Evaluation of Waste Tire Devulcanization Technologies

(INTERNAL REPORT) CENTERPLASTICS COMPOUND & ADDITIVES Feb. 2011 – M. S. Laura Fontana – Centerplastics Enterprise, Ltd Eastern Industrial Road, zip. 516127, Shiwan Town, Boluo Area, Huizhou, DongGuan, GuangDong, P. R. China PPH Chapter 1 – Introduction Approximately 25 potential devulcanization technology researchers and developers were identified throughout the world, however, only a very small number of devulcanization systems are now operating. These are primarily small-capacity systems, which are devulcanizing natural or synthetic rubbers (as opposed to devulcanizing the mixture of rubbers recovered from waste tires). The general types of devulcanization technologies identified and analyzed in the study are shown below. Technology Basis of Processing Zone of Reaction Chemical Chemicals/chemical reactions Surface of particles Ultrasonic Ultrasonic waves Throughout particles Microwave Microwaves Throughout particles Biological Microorganisms Surface of particles Other Mechanical Steam Surface of particles Key findings Reliable information and data on devulcanization of waste tire rubber are difficult to obtain due to proprietary claims, efforts to hide poor or infeasible process performance and product quality, and the limited number of technology researchers and developers and of peer-reviewed data. Reliable data relating waste tire characteristics, devulcanized rubber quality, end product performance, and production costs is scarce.  · Only a very small number of low-capacity devulcanization systems are operating in the United States (at approximately 50 Kg /hr, all R&D scale, mechanical, or ultrasonic). No proven commercial capacity units could be found that are currently devulcanizing waste tires, for example, at 500 Kg/hr or greater. The likely reasons include insufficient product quality and high costs of production.  · In terms of the potential of producing high-quality devulcanized rubbers (for example, high strength), the best technology appears to be ultrasonic, based on the current state of the art.  · Devulcanization of single rubbers has much more history than that of multi-rubber mixtures such as waste tires. Only a few companies devulcanize single formulation rubber as a result of captive conversion or merchant scrap recovery from manufacturing. The production of devulcanized rubber from home manufacturing scrap in the U. S represents about 1 to 2 percent of total U. S. rubber consumption.  · The quality of devulcanized single rubbers is higher than that of devulcanized multiple rubbers.  · Devulcanization that depends on surface devulcanization technologies (for example, chemical and mechanical) appears destined in the near term to produce low- or medium-quality devulcanized rubber material. The estimated cost for producing devulcanized materials from waste tires is $0. 3 to $0. 6/Kg  ± 30 percent, if including the cost of crumb rubber feedstock. This range of production costs is significantly greater than that of virgin rubbers. A typical tire compound contains the following constituents: Table 1. Composition of Tires Passenger Tire Constituents Common Materials Natural rubber 14 % Natural rubber Synthetic rubber 27% SBR, butadiene rubber Carbon black 28% Carbon black Steel 14%–15% Steel Fabric, fillers, accelerators, antiozonants, etc. 16%–17% Polyester, nylon, aromatic oil, coumarine resin, silica, bonding agent, stearic acid, ntioxidant, processing chemicals, sulfur, zinc oxide Truck Tire Natural rubber 27% Natural rubber Synthetic rubber 14% Synthetic rubber Carbon black 28% Carbon black Steel 14%–15% Steel Fabric, fillers, accelerators, antiozonants, etc. 16%–17% Polyester, nylon, aromatic oil, stearic acid, antioxidant, wax, processing chemicals, sulfur, zinc oxide Source: Rubber Manufacturers Association, 2004. †¢ Reclaiming is a procedure in which scrap tire rubber or vulcanized rubber waste is converted—using mechanical and thermal energy and chemicals—into a state in which it can be mixed, processed, and vulcanized again. The principle of the process is devulcanization (Franta, 1989). Historically and practically, in the concept of rubber reclaiming, devulcanization consists of the cleavage of intermolecular bonds of the chemical network, such as carbon-sulfur (C-S) and/or sulfur-sulfur (S-S) bonds, with further shortening of the chains also occurring (Rader, 1995). This description of devulcanization is different than that given below, which is limited to chemical interactions involving sulfur atoms. †¢ Reclaim is an interesting raw material as it reduces the production costs of new rubber articles, due to shorter mixing times and lower power consumption. The processing temperature is lower, and the material has a higher dimensional stability during calandering and extrusion due to the remaining three-dimensional network. The most important advantage of cured articles containing reclaim in terms of properties is an improvement of aging resistance. †¢ Devulcanization is the process of cleaving the monosulfidic, disulfidic, and polysulfidic crosslinks (carbon-sulfur or sulfur-sulfur bonds) of vulcanized rubber. Ideally, devulcanized rubber can be revulcanized with or without the use of other compounds. The different types of devulcanization processes also modify other properties of the rubbers. These processes cause diminution of some properties over those of the parent rubber. Ideally, devulcanization would yield a product that could serve as a substitute for virgin rubber, both in terms of properties and in terms of cost of manufacture. Polymers can be divided into two groups: thermoplastics and thermosetting materials. Thermoplastics soften when heated, making it possible to (re-)shape them at higher temperatures. Thermosetting materials, like rubbers, are crosslinked on heating and therefore cannot be softened or remodeled by raising the temperature. Therefore, thermosets are more difficult to recycle compared to thermoplastics. The three-dimensional network has to be broken in order to make the material (re-)processable: the so-called reclaiming process. In this process, either sulfur crosslinks connecting the polymer chains or carbon-carbon bonds in the polymer backbone are broken. The first mechanism is preferred, as the backbone of the polymer remains intact. Scission can be obtained by heat, shear or chemical reactions. Basically, processes of rupturing the rubber network by crosslink or main-chain scission can be classified into five main groups. †¢ Thermal reclaiming; †¢ Thermo-mechanical reclaiming; †¢ Mechano-chemical reclaiming; †¢ Reclaiming by radiation, and †¢ Microbial reclaiming. In actual practice, combinations of thermal and mechanical reclaiming are mostly used, with in some cases the addition of a devulcanization aid for chemical reclaiming. 1. 1-Thermal Reclaiming For this kind of processes, heat (often combined with addition of chemicals) is used to break the sulfur bonds and thus to plasticize the rubber. Hall patented in 1858 one of the oldest and most simple processes in the rubber reclaiming industry, the Heater or Pan process (Oil law). In this process, finely ground natural rubber powder is mixed with oils and reclaiming agents and treated with high or medium pressure steam at temperatures varying from 170 °C to 200 °C. The reclaiming time is long and the homogeneity of the reclaim is low, but this process is able to reclaim a large number of polymers: natural rubber (NR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR) and butyl rubber (IIR) and the equipment is rather inexpensive. The use of the heater or pan process became less popular after Marks patented the Digester or Alkali process in 1899. The fibers of the rubber scrap, remnants of the tire carcass, were first removed by mixing it with alkali, water, plasticizing oils and, if needed, chemical peptizers. The mixture was heated in a jacketed, agitator equipped autoclave to 180-210 °C. The most important disadvantage of this process is the pollution generated by the chemicals. Modifications of this process minimized the pollution, but increased the reaction times. Processes with short reaction times are for example the High Pressure Steam processes or the Engelke process. In the first process, a fiber-free, coarse ground rubber is mixed with reclaiming agents, and reclaiming is done in a high-pressure autoclave at approximately 280 °C. In the latter process, coarse ground rubber scrap is mixed with plasticizing oils and peptizers and is put into small autoclaves. The material is heated to very high temperatures for a short period of 15 minutes, after which it is lead through refiners (mills with very narrow gaps) and strainers. . 1. 1 – Steam With or Without Chemicals (Digester, DD-CR, HTDD-CR) Steam devulcanization of crumb rubber uses a steam vessel equipped with an agitator for continuous stirring of the crumb rubber while steam is being applied. There are two variants of the basis steam process, namely, â€Å"wet† and â€Å"dry. † The wet process uses caustic and water mixed with the rubber crumb, while the dry proce ss uses only steam. If necessary, various reclaiming oils may be added to the mixture in the reaction vessel. In one case, a wet process using diaryl disulfide and reclaiming oils with saturated steam at 190 °C (374 °F) was fed finely ground NR and synthetic rubber scraps. A charge of about 440 lbs. was partially devulcanized after 15 to 17 hours of processing. This process required 12 hours at ambient temperature for pre-treatment and 3 to 5 hours for steam or high temperature treatment (Adhikari, et al. , 2000). The dry process digester has the advantage of generating less pollution than the wet process. Scrap rubber containing natural and synthetic rubbers can be reclaimed by the steam digestion process. Reclaiming oil used for this process has molecular weights between 200 and 1000, consisting of benzene, alkyl benzene, and alkylate indanes. A generic processing diagram for steam devulcanization is shown in Figure A. Figure A. Schematic Diagram of a Steam Devulcanization System Devulcanized Rubber Dehydrating System Steam Reactor Rubber Crumb Chemical(s) Liquid By-Product 1. 2 – Thermo-Mechanical Reclaiming The thermo-mechanical reclaiming processes make use of shearing forces to plasticize the rubber. Energy is introduced into the materials, resulting in a significant temperature increase, high enough to cause thermal degradation. The Lancaster-Banbury process is one of the oldest processes. Fiber-free coarse ground rubber scrap is mixed with reclaiming agents and sheared in a high speed, high-pressure internal mixer. When a continuously working, multiscrew devulcanizer is used instead of the internal mixer, the process is called the Ficker reclaiming process. One of the first continuous reclaiming processes is the so-called reclaimator process. This is basically a single screw extruder that has been adapted to reclaim fibre-free rubber scrap in very short extrusion times. The short extrusion times make this method suitable for SBR, that tends to harden when longer recycling times are applied. Another mechanical reclaiming process is the De-Link process. In this process finely ground rubber powder is mixed with the De-Link masterbatch (DeVulc) : a zinc salt of dimethyldithiocarbamate and mercaptobenzothiazole in a molar ratio of 1:1 to 1:12, dispersed in thiols and activated by stearic acid, zinc oxide and sulfur. Advantages of the process are its simplicity and the fact that standard rubber equipment is used. No evidence is available to demonstrate that the De-Link process is used beyond laboratory or pilot scale. The Toyota process is another development of mechanical reclaiming. In this process a mixture of ground rubber, virgin rubber, oils and a devulcanization aid is masticated on a two-roll mill or in an extruder. Mechanical devulcanization is achieved through the repeated deformation of rubber particles under specific conditions of temperature and pressure. The result is a devulcanized rubber, ready for further processing. Toyota developed another continuous process, Toyota Gosei (TG) combining pulverization, reclaiming and deodorization. The rubber waste has to be ground to a particle size of 5-10 mm before it can be fed into a â€Å"modular screw-type reactor† with a pulverization zone and a reaction zone. The operating temperature is in the range of 100-300 °C and 100-900 rpm screw speeds are applied, the process requires about 100 Kw (kilowatts) to process 200 to 300 kg (kilograms)/hr of rubber, or approximately 0. 4 kW/kg. By manipulating screw configuration and rotational speed, and processing temperature, researchers are able to control the duration of the treatment. In this way they can, to some extent, control the properties of the devulcanizate. The TG process has been primarily, if not exclusively, used to devulcanize specific types of rubber compounds, such as NR and SBR. 1. 3 – Mechano-Chemical Reclaiming Mixing of the rubber powder with a peptizer (chemicals used to reduce the viscosity of NR) and a reclaiming agent prior to the mechanical breakdown of the material improves the reclaiming process. The devulcanization aid is supposed to selectively break the sulfur crosslinks in the rubber network. This chemical breakdown is combined with input of thermal and/or mechanical energy, as the rate of this process is sufficiently high only at higher temperatures. The most common devulcanization aids are disulfides, e. g. aryl disulfides or diphenyl sulfides, thiophenols and their zinc salts and mercaptanes. These chemical compounds are radical scavengers: they react with the radicals generated by chain- or crosslink scission and prevent recombination of the molecules. Typical concentrations for the reclaiming agents are 0. 5 to 4 wt%. Suitable peptizers are aromatic and naphthenic oils with a high boiling point. Figure B. Schematic Diagram of a Chemical Devulcanization System Devulcanization Agent Rubber Crumb Mixer Heated Extruder Devulcanized Filter Dryer Rubber Liquid By-Product Unfortunately, a detailed accounting of test materials, performance parameters, and conditions is lacking, thus inhibiting the extent of interpretation of the data. Comparisons of data are primarily limited to comparing the properties of virgin rubbers with compounds containing the virgin and devulcanized material at concentrations of about 30 percent devulcanized material. As shown by the data in the table, the properties of the mixtures containing devulcanized material are in general moderately lower than those of their virgin counterparts. The reported data reflect two different types of chemical devulcanization technologies. Table 2. Properties of Waste Tire Rubber Devulcanized Using Chemical or Chemical/Mechanical Technology Generic Technology Technology Surrogate Test Rubber Compound s % Devulc (or Ground) Mat'l Mooney Viscosity (ML-4 @ 212 °F) Tensile Strengt h (lbs/in2) 300% Modulus (lbs/ in2) Elongation to Break (%) Chemical STI-K Polymers DeLinka NR 0 61. 9 4,270 1,987 534 NR w/devulc NR 30 72. 3 4,020 2,151 489 Virgin SBR (1520) 0 96. 6 3,880 3,059 358 SBR (1520) w/devulc SBR 30 109. 2 3,580 2,923 345 Chemical/ Mechanical LandStar/ Guangzhou Research Instituteb NR 100 28. 4 680 SR 100 17. 2 514 AMRc Powder (devulc. additive) 100 23. 9 640 Tread Tire Compoundd 0 20. 3 772 28. 6 19. 7 628 Light Duty Truck Tire Compounde 0 23. 8 536 28. 6 20. 5 500 1. 4 – Reclaiming by Irradiation Bond type Dissociation energy (KJ/mol) C-C 349 C-S 302 S-S 273 Polysulfidic 253 Table 3. Typical bond energies 1. 4. 1 – Ultrasonic Rubber devulcanization by using ultrasonic energy was first discussed in Okuda and Hatano (1987). It was a batch process in which a small piece of vulcanized rubber was devulcanized using 50 kHz ultrasonic waves after treatment for 20 minutes. The process apparently could break down C-S and S-S bonds, but not carbon-carbon (C-C) bonds. The properties of the revulcanized rubber were found to be very similar to those of the original vulcanizates. One continuous process for devulcanization of rubbers is based on the use of high-power ultrasound electromagnetic radiation. This is a suitable way to recycle waste tires and waste rubbers. The ultrasonic waves, at certain levels, in the presence of pressure and heat, can quickly break up the three-dimensional network in crosslinked, vulcanized rubber. The process of ultrasonic devulcanization is very fast, simple, efficient, and it is free of solvents and chemicals. The rate of devulcanization is approximately one second. This may lead to the preferential breakage of sulfidic crosslinks in vulcanized rubbers. (Isayev, 1993; Yu. Levin, et al. , 1996; Isayev, et al. , 1997; Yun, et al. , 2001; Yun & Isayev, April 2003). Under a license from the University of Akron for the ultrasonic devulcanization technology, NFM Company of Massillon, Ohio, has built a prototype of the machine for ultrasonic devulcanization of tire and rubber products (Boron, et al. 1996; Boron, et al. , 1999). It was reported that retreaded truck tires containing 15 and 30 weight percent (percent by weight) of ultrasonicallydevulcanized carbon black-filled SBR had passed the preliminary dynamic endurance test (Boron, et al. , 1999). Extensive studies on the ultrasonic devulcanization of rubbers, and some preliminary studies on ultrasonic decrosslinking of crosslin ked plastics, showed that this continuous process allows recycling of various types of rubbers and thermosets (Isayev, 1993; Hong & Isayev, 2002 (pp. 160–168); Shim, et al. 2002; Shim & Isayev, 2003; Gonzalez-de Los Santas, et al. , 1999). As a consequence of the process, ultrasonically-devulcanized rubber becomes soft, therefore enabling this material to be reprocessed, shaped, and revulcanized in very much the same way as virgin rubber. This new technology has been used successfully in the laboratory to devulcanize ground tire rubber (commonly referred to in the industry as GRT) (Isayev, et al. , 1995; Yun, et al. , 2001; Boron, et al. , 1996), unfilled and filled rubbers N (Hong & Isayev, 2001; Yu. Levin, et al. , 1996; Isayev, et al. , 1997; Diao, et al. 1998; Shim, et al. , September 2002; Ghose & Isayev, 2003), guayule rubber (Gonzalez-de Los Santas, et al. , 1999), fluoroelastomer, ethylene vinyl acetate foam, and crosslinked polyethylene (Isayev, 1993; Isayev & Chen, 1994). After revulcanization, rubber samples exhibit good mechanical properties, which in some cases are comparable to or exceeding those of virgin vulcanizates. Structural studies of ultrasonically-treated rubber show that the breakup of chemical crosslinks is accompanied by the partial degradation of the rubber chain; that is, the C-C bonds (Isayev, et al. , 1995; Tukachinsky, et al. 1996; Yu. Levin, et al. , 1997 (pp. 641–649); Yushanov, et al. , 1998). The degree of degradation of C-C bonds can be substantial, depending on conditions. The mechanism of rubber devulcanization under ultrasonic treatment is presently not well understood, unlike the mechanism of the degradation of long-chain polymer in solutions irradiated with ultrasound (Suslick, 1988). Ultrasonic devulcanization also alters the revulcanization kinetics of rubbers. The revulcanization of devulcanized SBR appeared to be essentially different from those of virgin SBR (Yu. Levin, et al. , 1997, pp. 120–1 28). The induction period is shorter or absent for revulcanization of devulcanized SBR. This is also true for other unfilled and carbon black-filled rubbers such as ground rubber tire (GRT), SBR, natural rubber (NR), ethylene propylene diene monomer (EPDM), and butadiene rubber (BR) cured by sulfur-containing curative systems, but not for silicone rubber cured by peroxide. Ultrasonically-devulcanized rubbers consist of sol and gel. The gel portion is typically soft and has significantly lower crosslink density than that of the original vulcanizate. Due to the presence of sol and soft gel, the devulcanized rubber can flow and is subject to shaping. Crosslink density and gel fraction of ultrasonically-devulcanized rubbers were found to correlate by a universal master curve (Yushanov, et al. , 1996; Diao, et al. , 1999; Yushanov, et al. , 1998). This curve is unique for every elastomer due to its unique chemical structure. In a comparative analysis of ultrasonically reclaimed unfilled SBR, NR and EPDM rubbers, it was found that it was more difficult to reclaim EPDM than NR and SBR. Reclaiming of EPDM roofsheeting resulted in a good quality reclaim, which after revulcanization showed more or less equal mechanical properties compared to the virgin compound. The surface smoothness of the revulcanized compounds could be controlled by the process conditions. Most companies marketing ultrasonic devulcanization technologies are utilizing very similar technologies involving cold feed extruders and varying physical arrangements of ultrasonic equipment. Ultrasonic devulcanization technology is actually composed of a â€Å"devulcanization system†Ã¢â‚¬â€ namely, extrusion and ultrasonic processing. Two key differences in some cases are the equipment and materials used to generate the ultrasonic energy required for the process, and the positioning of the transducer(s) relative to the extruder. Two different arrangements of ultrasonic devulcanization systems are shown in Figures C and D. In this type of devulcanization system, size-reduced rubber particles are loaded into a hopper and are subsequently fed into an extruder. The extruder mechanically pushes and pulls the rubber. This mechanical action serves to heat the rubber particles and softens the rubber. As the softened rubber is transported through the extruder cavity, the rubber is exposed to ultrasonic energy. The resulting combination of heat, pressure, and mechanical mastication is sufficient to achieve varying degrees of devulcanization. The time constant of the devulcanization process takes place in seconds. Essentially all of the rubber entering the process is discharged from the extruder in semi-solid product stream. Process losses would be primarily those due to emissions of fine particulates or of gases, if any, generated due to the mechanical and thermal processes occurring during the devulcanization process. After exiting through the extruder die, the rubber is passed through a cooling bath and then dried. Figure C. Schematic Diagram of an Ultrasonic Devulcanization System Showing a Mid- Extruder Location for the Ultrasonic Subsystem Ultrasonic Processing Zone Cooling Bath Devulcanized Rubber Extruder Rubber Crumb Feed Hopper Figure D. Schematic Diagram of an Ultrasonic Devulcanization System Showing the Ultrasonic Subsystem Located at the Discharge End of the Extruder Ultrasonic Processing Zone Cooling Bath Devulcanized Rubber Feed Hopper Extruder Rubber Crumb Table 4. Properties of Waste Tire Rubber Devulcanized Using Ultrasonic Technology Technology Surrogate Test Rubber Compound s % Devulc or (Ground) Mat'l Mooney Viscosity (ML-4 @ 212 °F) Tensile Strength (lbs/in2) 100% Modulus (lbs/ in2) 300% Modulus (lbs/ in2) Elongation to Break (%) U of Akron SBR 1848a 0 2,415 740 780 SBR (1848) w/devulc SBRa 10 1,075 790 540 SBR (1848) w/whole train reclaima (10) 1,940 760 660 SBR (1848) w/30 mesh buffingsa (10) 1,440 780 480 100% NR (SMR CV60) & 0% SBR (23. 5% bound styrene, and Duraden 706)b 0 3,263 116 670 NR (SMR CV60) & 25% SBR (23. 5% bound styrene, and Duraden 706)b 0 1,885 123 600 NR (SMR CV60) w/devulc SBR (23. 5% bound styrene, and Duraden 706)b 25 580 123 380 NR (SMR CV60) & 50% SBR (23. 5% bound styrene, and Duraden 706)b 0 406 131 390 Technology Surrogate Test Rubber Compound s % Devulc or (Ground) Mat'l Mooney Viscosity (ML-4 @ 12 °F) Tensile Strength (lbs/in2) 100% Modulus (lbs/ in2) 300% Modulus (lbs/ in2) Elongation to Break (%) NR (SMR CV60) w/devulc SBR (23. 5% bound styrene, and Duraden 706)b 50 363 123 320 NR (SMR CV60) & 75% SBR (23. 5% bound styrene, and Duraden 706)b 0 363 145 295 NR (SMR CV60) w/devulc SBR (23. 5% bound styrene, and Duraden 706)b 75 276 131 250 100% SBR (23. 5% bound styren e, and Duraden 706)b 0 290 152 200 100% SBR (23. 5% bound styrene, and Duraden 706)b 100 290 138 180 Table 5. Percent Change from Virgin with Selected Devulcanization Rubber Formulations Test Rubber Compounds (grade) Parts or % % Devulc. or (Groun d) Mat'l. Hardnes s Shore Tear Strengt h Tensile Strengt h 100% Modulu s 300% Modulu s Elongatio n to Break Chemical STI-K Polymers DeLinka NR w/devulc NR 30 -5. 9% 8. 3% -8. 4% SBR (1520) w/devulc SBR 30 -7. 7% -4. 4% -3. 6% Kyoto Universityb Truck tire (93 NR+ 7 BR) 84 NR+ 6 BR + 20 devulc 18 8. 1% -2. 3% 2. 6% 0. 0% 74 NR+ 6 BR + 40 devulc 33 12. 9% -11. 9% 28. 2% -17. 4% 65 NR + 5 BR + 60 devulc 46 11. 3% -19. 1% 23. 1% -13. 0% LandStar/Guangzhou R Ic 100 SIR 10 + 50 devulc SIR vs. Case 1 33 4. 3% -23. 7% 6. 7% -6. 7% SIR vs. Case 2 33 6. 5% -23. 0% 11. 5% -8. 6% Tread Tire Compound 0 NR + 30 SR + 20 CIS-BR +40 AMR 28. 6 6. 7% -17. 3% -3. 0% -18. 7% Light Duty Truck Tire Compound 30 NR + 70 SR + 0 CIS-BR + 40 AMR 28. 6 1. 6% -10. 9% -13. 9% -6. 7% Retread Tire Compound c65 NR + 35 SR +40 AMR 28. 6 6. 3% -8. 6% -10. 3% -16. 8% Ultrasonic University of Akrond Versus Akrochem SBR (1848) SBR w/devulc SBR 10 -55. 5% 6. 8% -30. 8% Test Rubber Compounds (grade) Parts o r % % Devulc. or (Groun d) Mat'l. Hardnes s Shore Tear Strengt h Tensile Strengt h 100% Modulu s 300% Modulu s Elongatio n to Break SBR w/whole Tire Reclaim 10 -19. 7% 2. 7% -15. 4% SBR w/30 Mesh Buffings 10 -40. 4% 5. 4% -38. % Natural Rubber and SBR versus devulc Base 100% NR (SMR CV60) & 0% SBR (23. 5% bound styrene, and Firestone Duraden 706) 0 Add 25% SBR, 75% NR 0 -42. 2% 6. 3% -10. 4% Devulc SBR replaces SBR 25% devulc SBR, 75% NR 25 -69. 2% 0. 0% -36. 7% 50% devulc SBR, 50% NR 50 -10. 7% -5. 6% -17. 9% 75% devulc SBR, 25% NR 75 -24. 0% -10. 0% -15. 3% SBR versus devulc SBR 100% devulc SBR 100 0. 0% -9. 5% -10. 0% Heavy carbon-blacked rubber is the hardest to devulcanize, and silica, or other mineral-filled EDPM, is the easiest. Reincorporation of the devulcanized rubber is typically in the 20 to 40 percent range. Devulcanized single-product rubber applications are wide ranging. The reclaimed product may be reintroduced into the same end product or one with more tolerant performance characteristics for the devulcanized rubber. Devulcanized rubber seems to have advantages in bonding, strength, and tread integrity above the properties of crumb rubber, which acts only as a â€Å"rubber†-like filler. According to one developer of a devulcanization process, about 3 to 10 percent of the final product can be blended into virgin material before performance properties are affected. Variations of a few percent are reported by developers of devulcanization when they vary process run conditions. Run-to-run variations are normally acceptable. Devulcanized single rubber products have a much lower degree of degradation than multiple rubber mixtures with devulcanized rubber. Virgin single-grade SBR—or natural rubber replacement with devulcanized material shown by the STI-K and the University of Akron datasets —has, at worst, a reduction of 10 percent in tensile strength, modulus, or elongation. In some cases, the addition of devulcanized rubber causes a major reduction in performance of some properties, along with improvements in one or two properties (hardness and modulus). Because the modulus is the measure of deformation—that is, tension (stretching), compression (crushing), flexing (bending), or torsion (twisting). Similarly, the increase in hardness could be an improvement or detraction, depending on the application. The devulcanized rubber properties displayed are not necessarily optimized for a specific end use. Formulators will likely be able to incorporate devulcanized rubber along with other formulation components to achieve a higher level of final product performance. Key product performance variables are level of contamination, number of rubber types in the rubber mixtures, and additives used by the formulations. The effect of additives was discussed previously under â€Å"Product Characteristics. † The number of types of rubber in waste tires is one of the most important factors affecting quality of devulcanized waste tire rubber. Optimizing a devulcanization process is very difficult when more than one type of rubber is involved. Depending on the process used, process conditions, the material, and the blending level of the devulcanized rubber, most properties will be reduced by a few percent to more than two-thirds of those of the virgin material. In situations where the devulcanized rubber properties are within 10 percent of the original rubber material, blending would seem to be an attractive opportunity that offers the potential of adding a low-cost recycled substitute. The best operating model for devulcanizers of single rubber formulation is a dedicated devulcanization line (or long run) of specific rubber. Smaller volumes of single formulations require incurring extra costs for downtime and lost product caused by the cleanout between runs. The devulcanized rubber itself and some of its additives and fillers—such as carbon black— presumably add value. These fillers take the place of new additives and fillers that would otherwise be necessary. 1. 4. 2 – Microwave Microwave technology has also been proposed to devulcanize waste rubber (Fix, 1980; Novotny, et al. 1978). This process applies the heat very quickly and uniformly on the waste rubber. The method employs the application of a controlled amount of microwave energy to devulcanize a sulfur-vulcanized elastomer— containing polar groups or components—to a state in which it could be compounded and revulcanized into useful products such as hoses. The process requ ires extraordinary or substantial physical properties. On the basis of the relative bond energies of C-C, C-S, and S-S bonds, the scission of the S-S and carbon-sulfur crosslinks appeared to take place. However, the material to be used in the microwave process must be polar enough to accept energy at a rate sufficient to generate the heat necessary for devulcanization. This method is a batch process and requires expensive equipment. Figure E. Schematic Diagram of a Microwave Devulcanization System Rubber Crumb Microwave Unit Devulcanized Rubber Cooling System 1. 5 – Microbial Reclaiming Thiobacillus-bacteria are able to oxidise the sulfur in polysulfonic bonds to sulphate. This reaction is limited to a surface layer of the rubber with a thickness of less than 1 ? and the oxidation takes several weeks. The thiophilic bacteria Sulfolobus Acidocaldarius is able to split carbonsulfur bonds in a stepwise oxidation reaction of the carbon-bound sulfur into a sulfoxide, a sulfone and finally to a sulphate8, 9. The disadvantage of these processes is the low devulcanization rate. Apparently, these types of biological devulcanization processes are exclusively or primarily limited to the surface layers of the elastomers (Christiansson, et al. , 1998). This circumstance may explain the overall low rates of desulfurization based on total mass processed. Figure F. Schematic Diagram of Biological Devulcanization System Microorganisms and Host Media Mixer/ Reactor Rubber Crumb Devulcanized Rubber Dryer Filter By-Product Gases Liquid By-Product Chapter2 – Cost Analysis Given the lack of information in the literature, the cost estimates are based on a synthesis of information and data from multiple sources for a given generic type of technology; The analysis was generally performed by determining the costs (capital and operating and maintenance) of the processes and equipment described in the available literature. The cost analyses were conducted for three technologies that use different processing approaches: chemical, ultrasonic, and mechanical. * The key processing elements of each of these technologies have been previously described in this report, and they serve as the primary basis of estimating capital and operating and maintenance costs. The data in Table 6 summarize the capital costs and operating and maintenance costs for the technologies analyzed. The data for the capital cost analysis include an allowance for engineering services for the construction of the facility. The information shows that the capital costs for the processes vary from about $92,000 to about $166,000. ** Insufficient technical information and data were found during the study to enable reliable cost analyses for other devulcanization technologies. Table 6. Estimated Unit Costs for the Production of Devulcanized Rubber Item Mechanical Chemical Ultrasonic Capacity (lb/hr) 100 75 75 Capital Cost ($) 92,000 166,000 163,000 O Cost ($) 135,000 172,000 136,000 Amortized Capital and O ($) 143,000 186,000 150,000 Amortized Unit Cost ($/lb) 0. 7 1. 2 1. 0 Interest rate: 6% per year; Amortization period: 20 years Similarly, the data in the table indicate that the operating and maintenance costs for facilities of this type range from about $135,000 to $172,000. The operating cost estimates include the cost of crumb rubber feedstock for each of the processes. Based on the relative small size of the facilities, the costs of the rental of a building for processing in operating and maintenance are included. This eliminated the cost of building a structure. As shown in the Table, the estimated amortized costs for producing devulcanized rubber are: $1. 0/lb for the ultrasonic process, $1. 2/lb for the chemical process, and $0. 7/lb for the mechanical process. The analysis used an interest rate of 6 percent per year and an amortization period of 20 years. Due to uncertainties represented by the lack of detailed technical data and operating history for the technologies, the accuracy of the cost estimates is +/- 30 percent. As mentioned earlier, these costs reflect production at low capacities. Some reduction in unit cost would likely occur due to economies of larger scale production. However, estimating reduction in unit cost is difficult because of the lack of data relating to production costs to different levels of throughput capacity for particular devulcanization technologies. For the size of operations considered in this analysis, labor costs are a substantial portion of the production costs. It is very difficult, however, to estimate the magnitude of any potential reductions in unit labor costs that might occur if processing capacities were increased substantially. All circumstances considered, any estimates of commercial production costs for devulcanization of waste tire rubber are highly speculative at best. The best estimate of the study team is that perhaps production costs could be reduced by 25 to 30 percent if processing capacities were increased by a factor of approximately 5 to 10. The estimates of processing costs developed in this study do not include the costs of pollution control. The chapter lists the types of emissions that could be expected. The difficulty of permitting such a process and the cost of compliance with environmental regulations may comprise a significant barrier to the implementation of this technology. Conceivably, pollution control costs could add 10 to 30 percent to the cost of devulcanization. The difficulty of permitting—and the cost—would be a function of the type of devulcanization technology, the processing rates, and other factors. In general, the expectation is that the cost of environmental control systems for chemical devulcanization systems would be greater than that for ultrasonic or mechanical processes. The composition of rubber and additives that are used in rubber compounds in the manufacture of vulcanized rubber can and do have a dramatic effect on the properties of materials manufactured from devulcanized rubber. Apparently, the inferior properties of some poorly (inadequately) devulcanized rubber can be compensated for by the addition of chemicals and the adjustment of operating conditions, among other remedies. In many cases in the literature, this situation is not addressed or discussed. Consequently, comparing devulcanization technologies is difficult. From most of the literature descriptions of the processes, what happens to the sulfur and other vulcanization chemicals during the various processes is unclear. Chapter 3 – Environmental Analysis Little information is available in the literature on the environmental effects associated with waste tire devulcanization technologies. The lack of information apparently exists because business developers and researchers have concentrated their efforts primarily on technology improvements and achieving satisfactory properties for devulcanized rubber, an estimation of emission rates and a detailed environmental analysis are therefore not possible. However, using data and information from some other types of tire manufacturing processes (for example, extrusion of rubber) and the characteristics of vehicle tires, a qualitative analysis was performed. The environmental analysis described subsequently is limited to chemical and ultrasonic devulcanization and assumes that control of emissions would be required. 3. 1 – Chemical technology Chemical devulcanization processes are usually batch processes that involve mixing crumb rubber with chemical reactants at a specific temperature and pressure. Once the design reaction time has elapsed, the contents are then rinsed, filtered, and dried to remove any remaining unwanted chemical components. The product can then be bagged or otherwise processed for resale. A block flow diagram of a generic chemical devulcanization process is illustrated in Figure G, showing the raw material feed is crumb rubber. The crumb rubber is mixed with one or more devulcanization agents. Chemical agents identified as devulcanization agents are listed in Table 8. During processing in the batch reactor, vapors are released that must be collected and treated before release to the ambient atmosphere. Typical types of vapors that might be emitted from a batch reactor are listed in Table 9. The chemicals that would be vented from the batch reactor are dependent on the characteristics of the waste tire feedstock and on the chemical agent(s) used in devulcanizing the crumb rubber. For example, if disulfides are used in the process, they could result in formation of hydrogen sulfide (H2S) or methyl or other mercaptans (RSH). If the chemical agent orthodichlorobenzene is used, chlorinated hydrocarbons could potentially be released in the form of air emissions. Methyl iodide is volatile, and if used as a devulcanization agent, it could be vaporized. Since tire manufacturing utilizes zinc oxide and zinc carbonate, chemical devulcanization might also produce airborne metal particulates. Once the batch is fully processed, the reactor is vented. The vent gases are treated prior to release to the atmosphere. The vapors cannot be treated by vapor phase carbon because these chemicals will plate out and blind the carbon, making it ineffective. Instead, the vapor from the batch reactor needs to be thermally oxidized. At the high exit temperatures, typically as high as 2000 °F (1100 °C), the thermal oxidizer vent gases need to be cooled in a quench tower to approximately 300 °F (150 °C). Then, to remove any metals or other particulate, the vent gases are piped to a baghouse. Because of the high thermal oxidizer temperatures, methyl mercaptans (RSH) or hydrogen sulfide (H2S) from the crumb rubber is oxidized to sulfur dioxide (SO2). Therefore, downstream of the baghouse, a scrubber is required to remove sulfur dioxide (SO2), as shown in Figure G. Scrubbed vent gases are then released to the atmosphere. In addition to the scrubber vent gases described above, liquid waste is generated from the scrubber. This liquid stream contains sodium sulfate (Na2SO4). This liquid waste can be disposed in receiving waters such as a river, stream, or bay. However, discharging to receiving waters will require a significant amount of treatment equipment and eventually a permit. As seen in Figure G, the devulcanized rubber is moved from the batch reactor to a separator by a heated extruder. Liquid that drips off the devulcanized rubber is removed in the separator and eliminated by feeding it to the same thermal oxidizer as the vent gases from the batch reactor. After the liquid has dripped off the devulcanized rubber in the separator, any remaining moisture is removed in the dryer. Fired dryers are typically fueled by natural gas burners. Dryer vent gases are piped to the common thermal oxidizer. Based on the concentration of solids in the scrubber effluent, processing the scrubber effluent through a filter press to dewater the solids may be necessary and cost-effective. Filter-pressed dewatered solids are called â€Å"filter cake. Filter cake might require disposal in a hazardous waste site. Even though the waste disposal site may accept the scrubber effluent water, the economics may favor installation and use of a filter press. This is necessary to dewater the solids due to the high cost of disposal of liquid waste. Figure G. Block Flow Diagram of a Chemical Devulcan ization System Solids H2O Batch Reactor Heated Extruder Separator Crumb Rubber Devulcanization Agent 300 ° F Liquids Devulcanized Rubber Dryer Natural Gas Vapors Thermal Oxidizer Quench Tower Baghouse Natural Gas Scrubber 2000 ° F 300 ° F H2O Air Emissions Air Emissions to Atmosphere Effluent Water Table 7. Tire Raw Materials Polymers Antiozonants Natural Rubber (polyisoprene) 2,2,4-trimethyl-1,2-dihydroquinoline (polymer) Styrene-Butadiene Rubber (SBR) n,n-(1,3-dimethylbutyl)-pphenylenediamine cis-Polybutadiene copolymer paraffinic wax Vulcanizing Agents Antioxidants Sulfur Alkylphenols Tetra-methyl thiurame sulfide Resorcinol Accelerators 2,6-Diterbutylhydroquinone Diphenylguanidine Retarders 2-Mercaptobenzothiazole n-Cyclohexylthiophthalimide n-Cyclohexyl-2-benzothiazolylsulfenamide Plasticizers 2-(n-Morpholinyl)-mercaptobenzothiazole Aliphatic oil Hexamethylenetetramine Aromatic oil Activators Naphthenic oil Zinc oxide Di-(2-ethylhexyl)-phthalate Zinc carbonate Extenders Stearic acid Silica gel Carbon black Table 8. Chemical Agents Used in Chemical Tire Devulcanization Processes Triphenyl phosphine Sodium di-n-butyl phosphite Thiol-amine reagents (specifically propane-thiol/piperidine, dithiothreitol, and hexane-lthiol) Lithium aluminum hydride Phenyl lithium Methyl iodide Hydroxide with quaternary ammonium chloride as a catalyst Orthodichlorobenzene Diphenyldisulphide Diallyl disulfide Toluene, naphtha, benzene, and/or cyclohexane, etc. in the presence of sodium Diamly disulfide Dibenzyl disulfide Diphenyl disulfide Bis(alkoxy aryl) disulfides Butyl mercaptan and thiopenols Xylene thiols Phenol sulfides and disulfides Alkyl phenol sulfides (for SBR) N,N-dialkyl aryl amine sulfides (for SBR in neutral or alkaline solutions) 3. 2 – Ultrasonic technology Devulcanization by ultrasonic methods may be a continuous process (see Figure H). As the figure illustrates, crumb rubber is loaded into a hopper and is subsequently fed into an extruder. The extruder mechanically pushes and pulls the rubber. This mechanical action serves to heat the rubber particles and soften the rubber. As the softened rubber is transported through the extruder cavity, the rubber is exposed to ultrasonic energy. The resulting combination of ultrasonic energy, along with the heat, pressure, and mechanical mastication, is sufficient to achieve varying degrees of devulcanization. The exposure time to the ultrasonic energy is only seconds. Essentially all of the rubber entering the process is discharged from the extruder in a semi-solid product stream. Process losses would be primarily emissions of fine particulate or of gases, if any, resulting from the mechanical and thermal applications occurring during devulcanization. Since the typical operating temperature of an ultrasonic devulcanization reactor is about 230 °F (110 °C), less vapor emission would be expected than from chemical devulcanization. Furthermore, since no chemicals are added to break the sulfur bonds that caused vulcanization to occur, there would likely be lower air emissions. After exiting through the extruder die, the rubber is passed through a cooling bath and then dried. Vented vapors would need to be treated by one of two methods. One method would be to use a small thermal oxidizer. The design of the thermal oxidizer, baghouse, and scrubber would be similar to that described previously for chemical devulcanization. However, the physical size of the oxidizer would be smaller, and the baghouse and scrubber would be larger. A second method to treat the vent gases exiting the ultrasonic devulcanization reactor would be use of vapor phase carbon. In this method, due to the lower operating temperatures of the ultrasonic process, vent gas exiting the ultrasonic zone would have to be heated above the dew point temperature. If this elevation in temperature is not accomplished, the vent gases could condense on the surface of the carbon and thus blind the bed. In other words, adsorption sites on the surface of the carbon would be ineffective, and vent gases would exit the carbon bed untreated. If vapor phase carbon were to be used, the capital cost would be less than that of a thermal oxidizer. However, carbon is not very efficient. Weight loading can be approximately 10 weight percent—in other words, adsorbing ten pounds of vent gas contaminants for every 100 pounds of carbon used. Use of carbon will have a relatively high operating cost. Also, the disposal of spent carbon can be very expensive. This is especially true if the spent carbon requires disposal at a hazardous waste disposal site. Even if the carbon is regenerated on-site, adsorption efficiency decreases after each regeneration. Typically, carbon can only be regenerated ten times. For illustration purposes, Figure H indicates the use of vapor phase carbon. Devulcanized rubber exiting the ultrasonic processing zone has to be cooled. A common method of reducing the rubber temperature is a cooling bath. The volume of cooling water used would be significant. Cooling water may become ontaminated from the process; this effluent water leaving the cooling bath has to be treated. If an air cooler such as fin fans is used in lieu of water in the cooling bath, the volume of effluent liquid would be reduced. Another alternative would be to use a closed-loop cooling system, where the cooling water is cooled and returned to the process for reuse. If there is a buildup of contaminants, a small slipstream could be taken off and treated in a POTW, greatly reducing the amount of effluent that would otherwise require treatment. Figure H. Block Flow Diagram of an Ultrasonic Devulcanization System Ultrasonic Processing Zone Cooling Bath Devulcanized Rubber Feed Hopper Extruder Crumb Rubber Cooling Water Supply Effluent Water Heater Air Emissions Baghouse Carbon Air Emissions to Atmosphere Table 9. Potential Types of Chemical Compounds Emitted by Chemical and Ultrasonic Devulcanization Technologies Compound Probable Source Benzene Plasticizers: Aromatic oil Methylcyclohexane Plasticizers: Na phthemic oil Toluene Plasticizers: Aromatic oil Heptane Plasticizers: Aliphatic oil 4-Vinylcyclohexene Polymers: Natural Rubber (polyisoprene), styrene-butadiene rubber (SBR), cis- Polybutadiene Ethylbenzene Plasticizers: Aromatic oil Octane Plasticizers: Aliphatic oil p-Xylene Plasticizers: Aromatic oil Styrene Polymers: styrene-butadiene rubber (SBR) Nonane Plasticizers: Aliphatic oil 1,4-Cyclohexadiene-1-isopropyl-4- methyl Polymers: Natural Rubber (polyisoprene) Isopropylbenzene Plasticizers: Aromatic oil Cyclohexene-1-methyl-3-(1- methylvinyl) Polymers: Natural Rubber (polyisoprene) Propylbenzene Plasticizers: Aromatic oil Benzaldehyde Polymers: styrene-butadiene rubber (SBR) 1-isopropyl-4-methylcyclohexane (trans) Plasticizers: Naphthemic oil 1-isopropyl-4-methylcyclohexane cis) Plasticizers: Naphthemic oil 1-isopropyl-3-methylcyclohexane Plasticizers: Naphthemic oil Decane Plasticizers: Aliphatic oil Tri-isobutylene Polymers: styrene-butadiene rubber (SBR) & cis-Polybutadiene; Plasticizers: Naphthemic oil Cyclohexene-5-methyl-3-(1- methylvinyl) Polymers: Natural Rubber (polyisoprene) Indane Plasticizers: Naphthemic oil 1-Isopropyl-4-methylbenzene Plasticizers: Aromati c oil Cyclohexene-1-methyl-4-(1- methylvinyl) Polymers: Natural Rubber (polyisoprene) 1-Isopropyl-2-methylbenzene Plasticizers: Aromatic oil Dimethylstyrene Polymers: styrene-butadiene rubber (SBR) Undecane Plasticizers: Aliphatic oil Tetramethylbenzene Plasticizers: Aromatic oil 1,2,3,4-Tetrahydronaphthalene Plasticizers: Naphthemic oil 1,3-Di-isopropyl benzene Plasticizers: Aromatic oil 1,4-Di-isopropyl benzene Plasticizers: Aromatic oil Compound Probable Source 2-Isopropyl-6-methylphenol Antioxidents: Alkylphenols Cyclohexylisothiocyanate Retarders: n-Cyclohexyl-thiophthalimide Cyclododecatriene Polymers: cis-Polybutadiene Dodecane Plasticizers: Aliphatic oil Tridecane Plasticizers: Aliphatic oil Tetraisobutylene Polymers: styrene-butadiene rubber (SBR) & cis-Polybutadiene; Plasticizers: Naphthemic oil -ter-Butylstyrene Polymers: styrene-butadiene rubber (SBR) Dimethylpropylhexahydronaphthale ne Plasticizers: Naphthemic oil Tetradecane Plasticizers: Aliphatic oil Nonylbenzene Plasticizers: Aromatic oil 2,6-Di-ter-butyl-p-quinone Antioxidents: 2,6-Diterbutyl-hydroquinone Pentadecane Plasticizers: Aliphatic oil 1,6-dimethyl-4-isopropyl-1,2,3,4- tetra-hydronaphthalene Plasticiz ers: Naphthemic oil Decylbenzene Plasticizers: Aromatic oil Di-ter-butylthiophene Plasticizers: Aromatic oil Diethyl phthalate Plasticizers: Di-(2-ethylhexyl)-phthalate Hexadecane Plasticizers: Aliphatic oil ,2-Di-tolylethane Polymers: styrene-butadiene rubber (SBR) Heptadecane Plasticizers: Aliphatic oil 2,6-Di-ter-butyl-4-ethylphenol Antioxidents: Alkylphenols Octadecane Plasticizers: Aliphatic oil 1-Phenylnaphthalene Plasticizers: Aromatic oil Di-iso-butyl phthalate Plasticizers: Di-(2-ethylhexyl)-phthalate Tridecylbenzene Plasticizers: Aromatic oil Dibutyl phthalate Plasticizers: Di-(2-ethylhexyl)-phthalate Eicosane Plasticizers: Aliphatic oil Heneicosane Plasticizers: Aliphatic oil Docosane Plasticizers: Aliphatic oil Di-(2-ethylhexyl) phthalate Plasticizers: Di-(2-ethylhexyl)-phthalate Chapter 4 – Conclusions Devulcanization of specific types of rubber and/or waste tire rubber has a long history. However, only recently have limited technical data been reported in the available literature. Usually when reported, the tested properties of devulcanized rubber compose an incomplete list. This is especially true in the interpretation of how the devulcanized product would perform during compounding, in the manufactured end product, or both. Circumstantial and anecdotal evidence indicates significant technical and economic barriers to devulcanization of waste rubber. Based on the information collected in the study, is believed that the only method of achieving bulk devulcanization, as opposed to surface devulcanization, rests with ultrasonic or microwave devulcanization methods. Of these two methods of energy application, ultrasound appears to have substantially more research and development history. An important observation is that microwave technology is not an effective or efficient way to devulcanize non-polar rubber types, which collectively compose the vast majority of the mass of rubber in waste rubbers. Because of the ability to internally devulcanize cured rubber, ultrasonically devulcanized waste tire rubber may have more desirable marketing characteristics than those of surface-devulcanizing processes under similar conditions of cost and yield. The latter processes (surface devulcanizing) include mechanical, chemical, and biological processes. However, test data and applications for ultrasonically devulcanized waste rubber are lacking in the industry, along with process cost documentation. The devulcanized rubber market is most fully developed for single product materials made from manufacturing scrap that are reclaimed for reuse in the same process or in a broader specification application. The reprocessing of single rubbers depends upon being located near a large-volume rubber products company with enough scrap and enough rubber applications to justify the devulcanization step. Devulcanization of waste rubber, despite considerable research and developmental effort, is still in an early growth stage. Devulcanization lacks adequate test data and data interpretation, and it has poorly defined end product specifications without adequately justified and defined applications and uses. Research funds appear to be most available for studying devulcanization of single rubber types, as opposed to studying rubber types with complex mixtur. In applications already using crumb rubber, devulcanized rubber can have advantages if the process combines a vulcanized rubber or other compatible material to create an integrated structure. The structure must have much better properties than those imparted by the filler role that crumb rubber frequently serves.

Pets Should Be Treated As A Member Of The Family

Should we treat pets like human beings? Some people believe that pets should not be treated like human beings because people spend too much money on their pets. For example, they spend money on their insurance, on their health and many more. In other hand, many people believe that pets should be treated like human beings. Those people believe that pets have emotions as human beings. I think that it is a right approach to treat pets as members of the family because pets share the same living space with us, bring us a lot of joy and emotions.People usually bring pets in their houses for various reasons. People with disabilities have pets which helps them in many different ways, for instance, dogs can provide help to the disable people in daily activities. Therefore, these people need someone like pets all day around to feel themselves secure. They need someone on whom they can rely when doing basic things such as crossing the roads or stepping down the stairs.These are the things that normal people do habitually however; for people with disabilities these are the challenges they have to deal with every day. It goes without saying that pets that help people to cope with everyday life are truly family members and should be rewarded for their sacrifice to human beings. Why then pets should not be treated like human beings if they share some of the characteristics that relate to humans? On the other hand, pets are not like any other animals in our planet.We should give them respect their dignity even if they are just animals. When Pets are ill should be given most care and love as we are giving it to our children. We have to give a certain portion of attention as we are giving it to our children. Pets are not that intelligent as humans but they feel that we love them and pay us in the same way by helping our life. In conclusion, I think that pets deserve to be treated as human beings since they help us to overcome difficulties.

Asymmetric Synthesis Essay Example | Topics and Well Written Essays - 1000 words

Asymmetric Synthesis - Essay Example Hence, it is undeniably interesting to study the catalytic asymmetric synthesis of cinchona alkaloids , which have also been helpful in man's daily living. This includes its role in the production of food flavorings and medicines for different ailments like malaria. Additionally, the popularity of cinchona alkaloids over the years is also because of its qualifications in the three primary criteria of catalysts, which are as follows: 1) the diversity of reactions that the catalyst can trigger; 2) the accessibility of both enantiomeric antipodes of the catalyst at an affordable cost; and 3) the stability of the catalyst. The research aims to study the catalytic asymmetric synthesis of the popular two pairs of cinchona alkaloids which are enantiomeric in nature: cinchonine and cinchonidine, and; quinine and quinidine. The researcher aims to study the two pairs by isolating them through extraction of the bark of the cinchona tree; a native of tropical regions. Due to their widespread use, all four members are readily available in large quantities from most chemical suppliers. Furthermore, before conducting several experiments for the research, the researcher will gather enough materials documenting the history of cinchona alkaloids. ... erature section of the research, which will include information about cinchona alkaloids from one of the earliest uses of cinchona alkaloids in asymmetric catalysis which was demonstrated by Pracejus in the 1960's to catalyze the asymmetric alcoholysis of ketenes (Pracejus, 1964) to its modern uses. Moreover, the study's related literature will consist of theories proposed about the asymmetric synthesis of cinchona alkaloids by chemists of different ages. One interesting theory which will contribute to the study of the alkaloid's catalytic asymmetric synthesis is that the alcohol is activated via a hydrogen bond with the tertiary amine of benzoylquinine. Addition of the alcohol to the ketene is followed by quenching of the resultant enolate by the chiral ammonium salt. The resultant esters are isolated in up to 76% enantiomeric excess. The research will strive to replicate the experiments conducted to support this theory. Also, with the proliferation of recent publications studying cinchona-ketene systems for asymmetric synthesis (Blake, 2001), the study will investigate different assumptions about the asymmetry in the synthesis of cinchona alkaloids. One of the most noticeable of these recent publications which the researcher intends to focus is Lectka's -halogenation of acid chlorides (Wack, 2001). Lectka stated that the benzoylquinine-ketene system reacts with quinone based electrophilic halogenating reagents to yield activated -halogenated esters with enantioselectivities as high as 99%, and with good yields. The study will try to prove this through catalytic asymmetric fluorination, where cinchona derivatives have already been used, though only stoichiometrically (Muiz, 2001). However, despite the efforts to base certain experiments upon previous studies, the

Psychopharmacology and the Mental Health Counselor Assignment

Psychopharmacology and the Mental Health Counselor - Assignment Example Thus, most of these conditions can be treated with a variety of behavioral and cognitive therapy techniques, but what happens when a patient comes in and has a psychological condition that is based off a chemical imbalance in the brain. This requires the use of psychopharmacology to regulate the chemical imbalance in order to change the abnormal behavior. Most counselors do not have the appropriate knowledge to know the entire effects of drugs on their patients. According to Buelow, Hebert, and Buelow (2000), many counselors do not have enough knowledge in the area of psychopharmacology to adequately provide medication for patients. Juxtaposed, many treatment models now incorporate a hybrid technique dealing with both therapy and the use of pharmaceuticals. The counselor should also be aware of the patient’s wishes when talking about drug therapy. It is recommended that the counselors become sensitive to the patient’s feelings regarding pharmacotherapy, the patient†™s previous experience with the negative side effects of drugs, nonadherance of the patient to the set regiment and the patient’s use of drugs and alcohol (Meyer & Simon 1999b). Client education of the drugs used in practice is also important. The first priority is determining whether the illness requires the use of medication or not.

Molecular and ellular Biology Essay Example | Topics and Well Written Essays - 2500 words

Molecular and ellular Biology - Essay Example Genes may be incorporated into bacteria, plants or animals. In this process recombinant DNA (rDNA) technology is used to incorporate gene of interest into organisms and that organism in which gene is inserted is said to be genetically engineered. Through this process off springs with unique characters are produced. Recombinant DNA is also referred to as Chimera. By the combination of two different strands of DNA a new strand of DNA is obtained. The first step in genetic engineering involved the production of hormone insulin which is important and helps the cells to properly absorb sugar. In recombinant DNA technology recombinant DNA is made by splicing a small fragment of a foreign DNA into a small molecule that can replicate on its own such as bacterial plasmid as a result a clone of inserted DNA can be obtained. AN organism that receives a foreign DNA is called transgenic organism and these organisms can be used in research or in commercial applications such as production of human insulin in transgenic bacteria (which receives genes from human responsible for the production of insulin). This application gives the idea that how important DNA recombinant technology is.(Recombinant DNA technology). Two classes of enzymes play an important role in DNA recombinant technology. Restriction endonucleases: They recognize specific sites on DNA and cleave DNA at that site into smaller fragments. DNA ligases: They link the foreign DNA with the vector DNA. Cloning of DNA involves the following steps: 1: First step in making recombinant DNA is to isolate donor and vector DNA. 2: Cloning vector is cleaved with restriction endonucleases. 3: gene of interest is obtained by cleaving chromosome of foreign DNA with the same restriction endonuclease into smaller fragments. 4: Fragments are ligated to the cloning vector by DNA ligase as a result a recombinant vector is obtained. 5: This recombinant DNA is introduced into the host cell where it replicates and produces copies of recombinant DNA. (Lehninger, Principles of Biochemistry fourth edition). Recombinant DNA technology in the synthesis of insulin: Insulin is an important hormone which regulates the storage of carbohydrates in the body. It is secreted by the beta cells present in the pancreas islets of langerhans. Insulin is a small protein and is composed of two polypeptide chains which are linked together by disulfide bonds. When blood glucose level is high insulin is secreted into the blood stream and removes excess of glucose from the body. Human insulin is the only known protein which can be produced in bacteria by DNA recombinant technology in a way that its structure and composition resembles the original molecule. In diabetes patients problems are associated with the production of insulin due to which sugar increases to dangerous levels which could be life threatening. These patients are treated with insulin which is produced in another organism. Although insulin can be produced in animals whose insulin resembles human insulin in terms of composition with minor variations like bovine and porcine insulin but, it was observed that when bovine and porcine insulin were injected into the patient’s body antibodies were produced against them thereby, neutralizing it’s action and producing inflammatory response at the site of injection. These problems suggest that a suitable vector like E.coli could be used to produce insulin. E.coli is a common inhabi tant of the human digestive tract and is a key organism used in the production of insulin by genetic engineering. Following are the steps involved in the production of insulin from a bacterial host. 1: Isolate gene: The gene that produces insulin in human is isolated and is

Commodities, mining, FDI, and the awakening Chinese dragon. Where next Essay

Commodities, mining, FDI, and the awakening Chinese dragon. Where next for China - Essay Example China’s open door policy does not only serve as the catalyst for the robust economic growth of China, it is considered as the primary impetus, strongest and decisive factor catapulting China as one of the most powerful economy in the 21st century (Chen 2012; Liu and Daly 2011; Yao 2006). This supposition is maintained on the premise that with the open-door trade policy of China, the country has become the preferred country of foreign investors and as such, recipient of numerous foreign direct investments (FDI) (Yao 2006). From 2000- 2011, China received the largest FDI inflows compared with other developing or transition economy (Davies 2012). In 2011 alone, China’s FDI inflows has reached US$124 billion compared with other countries such as Brazil with US$ 67 billion, Russia with US$ 53 billion, Singapore with US$ 64 billion, and India with US$32 billion (http://stats.unctad.org/fdi/). This shows the continued confidence of investors to China. China’s good perfo rmance in the 1997-1998 Asian crises and the recent global economic slump affirms the view that China’s economy is resilient and China offers a reliable risk-avoidance haven that is suitable for international investors (Davies 2012) as the country continuously moves towards becoming the world’s largest economy (Davies 2012). In this regard, the research will look into the impact of FDI in China with specific focus on the mining industry. This is important, as China is responsible for the net growth in world demands since 1995 (Evans –Pritchard 2012). In fact, just recently, China’s growth contributed to the appreciation of copper in the market (Rowley and White 2012).However, Rio Tanto has announced cost-cutting measures in operating costs across the business amounting to $ 5 billion by 2014, while BHP Billiton is diversifying its portfolio (Rowley and White 2012). In addition, there is apprehension across the mining industry since China is shifting to â €Å"modern, sleek, consumer and service driven economy† (Evans-Pritchard 2012,  ¶ 9). The slowdown in China’s economy and macro-volatility of the global market feed the apprehensions in the mining industry On the other hand, Vivoda (2011) argues China is mining industry continuous to lag behind other industries in terms of foreign investments. In fact, the government consistently reforms and rectifies foreign trade policies to attract investors in the mining sector of the country; nonetheless, foreign investors steer away from China because of uncertainty and lack of transparency within the mining industry (Suxun and Chenjunnan 2008). In the face of this dichotomy in position pertinent to China’s mining industry and FDI, the research may help in clearing some concepts that conflates the trepidation concerning China’s economic slowdown. In addition, some limitations are observed in terms of focus in existing literatures that deal with the issue (Vivoda 2 011). Most literatures tackle specific country/ regional concerns or undertake comparative studies (Vivoda 2011). In this regard, the study contributes to the existing literature, as it will try to explore the developments within China’s mining industry vis-a-vis FDI and understand the impact of the industry to the country as China moves towards bec

Employee retention Essay Example | Topics and Well Written Essays - 1750 words

Employee retention - Essay Example One of the first things a company can implement to retain employees is to offer benefits both tangible and intangible. According to the article â€Å"His job: helping employers hold on to their staff; High turnover can be costly. Consultant says its vital to offer respect, good pay, retirement plan† by Kasandra Kyle the most important thing that a potential employer can offer a new employee is good pay, respect and a retirement package . These benefits help make employees comfortable in their current position and will retain an employee sometimes even when another job offer with a more lucrative offer comes around. Another fringe benefit is the flexible work schedule. Although this is not practical in all cases, if it is at all possible it serves as an excellent retention strategy. Offering tangible and intangible benefits are essential, but it is imperative to work diligently to keep specialty trained staffers. The low turnover of maintaining skilled employees offers the benefits of low turnover and positions companies for growth. The author goes on to say that the cost of training specialty staffers can cost the company valuable time, enormous finances and slowed production (Kyle, 2008). Although it is important to offer workplace benefits at your larger companies, it is dire to offer those benefits at a small business. The article, â€Å"Workplace benefits are strategic in small business† states that recent study performed by MetLife’s annual Employee Benefits Trends study shows more than half (55%) of smaller employers, those with fewer than 500 employees say benefits play a very important role in employee retention. However, there is contradictory results as the study goes on to reveal that only 34% of workers at smaller employers say the benefits they receive are a very important reason to remain with their employer, versus 53% at larger firms. In addition, just 37% of employees at smaller corporations say they are

Project Risk and Procurement Management Essay Example | Topics and Well Written Essays - 2500 words

Project Risk and Procurement Management - Essay Example The study investigates global catalogue facility in IBM that supports strategies aimed at offering IBM innovative catalogue solution for indirect purchases while supporting all teams in need of catalogue functionality. Issue at hand Procurement teams face challenges as well as opportunities from the increased competition, accelerated globalization and growth of services as essential differentiators in the marketplace, it is essential for organizations have to reassess their prevailing strategy and constantly validate its efficiency based on current and expected future business environment. At the core of IBM’s integrated supply chain is its global procurement’s value coming from its people and technologies that secure goods as well as service in support of internal partners and external clients in development and delivery of quality products and offerings (Williams, Lueg & LeMay 2008). IBM’s global supply chain involves a large number of suppliers is used to addr ess every product and service offering the company produces. Devising supply chain of this dimension and complexity while attaining end-to-end perceptibility and total incorporation is not a small task. Collaboration with suppliers and business partners remains crucial for the company in today’s business because it enables communication in the supply chain and ensures that suppliers are agile and responsive. Currently, the company’s supply chain is complex and functions much like a multi-point network configuration with movement of goods, processes and communications essential to the network (Baraldi 2008). Concept of supply chain management Supply chain management in the past few decades became extremely essential to companies operating in the competitive global marketplace. Although there are many definitions on the concept of supply chain, supply chain entails the context in which goods, services and information flow from the supplier to the end user; however, in re cent past supply chain expanded to include flow in the opposite direction. Therefore, supply chain management entail effective and efficient supervision of the supply chain and relationships between parties taking place in the chain. The significance of supply chain management is often associated with benefits it offers to organizations in the chain because it offer benefits like decreased costs, boosts revenue, increases satisfaction in customers and improves delivery and product or service quality. The benefits arise from various factors associated with supply chain management like information sharing, coordination and the resulting synergies between organizations (Baltacioglu, Ada, Kaplan, Yurt & Kaplan 2007). Moreover, through supply chain management, market data needs can efficiently be monitored and changing consumer needs and demands can easily be accessed and satisfied through proper production processes. As well, providing the right products and services at the right time a nd location offers customer satisfaction, and this potentially increases sales and revenue. Supply chain is essential considering that in the current global market it is impossible

Crooks Essay Example for Free

Crooks Essay Crooks as the biggest victim on the ranch discuss Monday 24th October 2011 In the novel ‘Of Mice and Men’ Steinbeck presents Crooks, the black stable-buck as the biggest victim on the ranch because of his race. Crooks is also the most damaged person, emotionally and physically. He has a crooked back and has begun to mimic the cruel and violent behaviour of the other men on the ranch. The impact of his loneliness also makes him push people away, leaving him even more lonely and segregated. The other men exclude Crooks because he is black. He is not allowed to go into the bunkhouse with all the white men because they are racist and follow the racist behaviour of segregation. It is clear that Steinbeck is critisising wider society through his description of Crooks. Crooks has his own room ‘had his bunk in the harness room’ he lives alone and is no more important than the animals symbolised by the nearness to the animals. He is alone all the time and gets lonely but never admits it because he is too proud. Steinbeck show’s the irony of Candy saying ‘must be nice to have a room all to your self’. When Lennie comes in to his room, Crooks has right to ask him to leave but instead acts as though he didn’t want Lennie to stay. He says – ‘come on in and set a while†¦long as you wont get out and leave me alone. ’ The ellipsis’ show his hesitation after he admitted he wants the company he realizes and changed it around to say he wants to be alone. This is so Crooks can maintain his pride and his dignity. He his so lonely that he admits to Lennie – ‘just a guy talking to another guy doesn’t matter if he understands. ’ This tells us Crooks is happy talking to Lennie even though Lennie does not understand most of the things Crooks is saying. It is the company and the talking to another human that matters to him. Steinbeck also adds that Crooks ‘reads a lot’. Steinbeck implies that even though Crooks is treated badly he could be the most educated worker on the ranch has a better understanding of things than most of the other men and is wiser because he is older and has seen more things. Also he has a ‘Californian Civil Code’ book, because he has this book and reads it often he knows a lot about the laws of discrimination in different areas. He is interested in is rights as a black man unfortunately, despite his knowledge Crooks is unable to change anything. Slim is the only man who treats Crooks sympathetically. He respects Crooks more and talks to him some times. Slim is ‘kind’ and ‘is a good listener’ but Slim and Crooks are the opposite- Slim is respected and has power whereas Crooks is disrespected and beaten by the men because of the colour of his skin. Slim is a ‘tall man’ who is ‘capable of killing a fly on the wheelers butt without touching the mule’ but Crooks was just a ‘stable buck, nigger with a ‘crooked back’. Through this contrast, Steinbeck provokes pathos about Crooks’ life. Ironically, even Slim is effected by the hardship on the ranch casually drowns four pups. Steinbeck depicts Crooks as the most physically damaged person on the ranch. One of the reasons for this is that the white men beat Crooks, just because he was black. The boss uses Crooks to let his anger out – ‘the boss gives him hell when he’s mad. ’ Even though the boss hired Crooks to do a job he beats him when he is angry, this shows Crooks is of a low status on the ranch and that he matters the least. The men are also very cruel to Crooks when they say ‘ Jesus we had fun. They are referring to a time when they beat Crooks. This is very cruel he had no way of defending himself by fighting back because he has a crooked back and is much weaker he also has no one on his side. What is more brutal is that they did it just for pleasure this suggests that the ranch is corrupting everyone. Steinbeck warns us of the consequences of brutality in the wider world. Furthermore the cruelty Crooks faces made him cruel to Lennie when he says – ‘I don’t blame the guy you travel with for keeping you outta sight. ’ and ‘what if he don’t come back. Crooks wants to frighten Lennie and is clearly jealous of the companionship he has with George. When ‘Crooks face lightened with pleasure in his torture’ it shows that Crooks has learnt from the other men how to be cruel. This is also another way he has been damaged emotionally by the ranch because most of the men become cruel and it is a violent world where only the fittest will survive. Crooks wishes that he could have what George and Lennie have so he gets dragged in to the dream against his better judgment – ‘Never a god dammed one of em gets it just like hea ven. Here is Crooks talks about men trying to get land for themselves. He does not believe in God because his life has been so bad that there cannot be a God but he still equates land with heaven. Crooks is lonely and has a room to himself on the ranch and in it there were ‘hung broken harness strips in process of being mended, strips of new leather. ’ Ironically ’Being a stable buck he was more permanent than other men’ His permanency does not give him status he is all alone and unlike the bunk house where games are played in the evenings his room is filled with work objects so he would not get much time to relax or rest. Also in his room is ‘a range of medicine bottles for himself and the horses. ’ This is another example of him being no more important that the animals and also part of the discrimination against him. Steinbeck depicts Crooks as a victim by the description of his physical appearance. – ‘His body was bent over to the left by his Crooked spine’ His lean face was lined with deep wrinkles, and he had thin, pain-tightened lips which were paler than his face. ’ His body is bent over because a horse has kicked him on the ranch so the ranch damages him physically. His lined face shows the evidence of the brutality of the ranch, he is older and weaker because of the hard work he has done and his thin, pain-tightened lips show the pain he is in. yet he still has to work everyday and he tries to soothe the pain by repeatedly applying liniment to his back. This reminds us of his pain – ‘he poured his liniment into his pink palmed hand. ’ Although Crooks is damaged by the ranch and has no status, he is a very proud, dignified man who wants people to respect the few rights he has, ‘you got no right to come in here’ he said to Lennie because his room was the only thing people has respect. He has read about black rights, he is interested in what rights he could have in other places. Although Crooks had the right to ban Candy and Lennie from his room the desire for company overrode this. He was happy to have the company of the two men, ‘well, why’n’t you kick ‘em out? ’ ‘I di’nt care much’. Steinbeck makes us sympathise with Crooks as he is presented as the biggest victim on the ranch because he is damaged mentally, physically and emotionally. Steinbeck also makes us sympathise with Crooks because he is lonely and how he is lonely from the isolation from the other men.

College Is Not for Everyone Essay Example for Free

College Is Not for Everyone Essay Going away to college is not for everyone. There are good reasons why a student might choose to live at home and attend a local school. Money, finding stability while changes are occurring, and accepting responsibility are three to consider. Money is likely to be most important. Not only is tuition more expensive, but extra money is needed for room and board. Whether room and board is a dorm or an apartment, the expense is great. Most students never stop to consider that the money that could be saved from room and board may be better spent in future years on graduate school, which is likely to be more important in their careers. Going to school is a time of many changes anyway, without adding the pressure of a new city or even a new state. Finding stability will be hard enough, without going from home to a dorm. Starting college could be an emotional time for some, and the security of their home and family might make everything easier. When students decide to go away to school, sometimes because their friends are going away, or maybe because the school is their parents’ alma mater, something that all need to decide is whether or not they can accept the responsibility of a completely new way of life. Everyone feels as if they are ready for total independence when they decide to go away to college, but is breaking away when they are just beginning to set their futures a good idea? Going away to school may be the right road for some, but those who feel that they are not ready might start looking to a future that is just around the corner.