Rubber compounding synthetic elastomers

The elastomer determines most of the physical and chemical characteristics of a rubber compound. Typical elastomers are natural elastomers such as natural rubber (NR), sometimes called crepe, and synthetic elastomers such as butyl (including chlorobutyl and bromobutyl), ethylene propylene diene monomer (EPDM), and styrene butadiene rubber (SBR). A list of commonly used elastomers is shown in Table 2. 

In the raw state elastomers tend to be soft and sticky when hot, and hard and brittle when cold. Compounding increases the utility of rubber and synthetic elastomers. Vulcanization extends the temperature range within which they are flexible and elastic. In addition to vulcanizing agents, ingredients are added to make elastomers stronger, tougher, or harder, to make them age better, to color... 

Plastics and Elastomers. Common plastics and elastomers (qv) show exceUent resistance to hydrochloric acid within the temperature limits of the materials. Soft natural mbber compounds have been used for many years as liners for concentrated hydrochloric acid storage tanks up to a temperature of 60°C (see Rubber, natural). SemUiard mbber is used as linings in pipe and equipment at temperatures up to 70°C and hard mbber is used for pipes up to 50°C and pressures up to 345 kPa (50 psig). When contaminants are present, synthetic elastomers such as neoprene, nitrile, butyl. 

Among the different pressure sensitive adhesives, acrylates are unique because they are one of the few materials that can be synthesized to be inherently tacky. Indeed, polyvinylethers, some amorphous polyolefins, and some ethylene-vinyl acetate copolymers are the only other polymers that share this unique property. Because of the access to a wide range of commercial monomers, their relatively low cost, and their ease of polymerization, acrylates have become the dominant single component pressure sensitive adhesive materials used in the industry. Other PSAs, such as those based on natural rubber or synthetic block copolymers with rubbery midblock require compounding of the elastomer with low molecular weight additives such as tackifiers, oils, and/or plasticizers. The absence of these low molecular weight additives can have some desirable advantages, such as ... 

The pneumatic tire has the geometry of a thin-wallcd toroidal shell. It consists of as many as fifty different materials, including natural rubber and a variety ot synthetic elastomers, plus carbon black of various types, tire cord, bead wire, and many chemical compounding ingredients, such as sulfur and zinc oxide. These constituent materials are combined in different proportions to form the key components of the composite tire structure. The compliant tread of a passenger car tire, for example, provides road grip the sidewall protects the internal cords from curb abrasion in turn, the cords, prestressed by inflation pressure, reinforce the rubber matrix and carry the majority of applied loads finally, the two circumferential bundles of bead wire anchor the pressnrized torus securely to the rim of the wheel. 

This group of synthetic elastomers is better known under the trade name ThiokoP. Polysulphide rubbers are condensation polymers of sodium poly sulphide and dichloro-compounds they have outstanding resistance to swelling by oils and solvents but tensile strength is... 

Uses Solvent for elastomers, natural rubber, synthetic rubber heat-transfer liquid transformer and hydraulic fluid wash liquor for removing C4 and higher hydrocarbons sniff gas recovery agent in chlorine plants chemical intermediate for fluorinated lubricants and rubber compounds fluid for gyroscopes fumigant for grapes. Not produced commercially in the U.S. 

Zinc peroxide is used as an accelerator in rubber-compounding, as a curing agent for synthetic elastomers, and as a deodorant for wounds and skin diseases. Zinc peroxide is a powerful ini taut to skm, eyes, and mucous membranes. The systemic toxicity is similar to that of zinc oxide, for which the LD o (rat, oral) is 7950 mg/kg. 

Modem civilization consumes vast quantities of organic compounds. Coal, petroleum, and natural gas are primary sources of carbon compounds for use in production of energy and as starting materials for the preparation of plastics, synthetic fibers, dyes, agricultural chemicals, pesticides, fertilizers, detergents, rubbers and other elastomers, paints and other surface coatings, medicines and drugs, perfumes and flavors, antioxidants and other preservatives, as well as asphalts, lubricants, and solvents that are derived from petroleum. 

The development of silicone elastomer technology has enabled synthetic rubber plants to obtain very convenient and practical rubber compounds. 

Meissner, B., Schatz, M. and Brajko, V., Synthetic Rubbers Epichlorohydrin Rubber , in Studies in Polymer Science. Vol. 1. Elastomers and Rubber Compounding Materials, Elsevier, Amsterdam, 1989, pp. 274-278. 

This compounded cured elastomer or rubber99 shares with all the other methyl silicone products the common characteristic of exceptional thermal stability. The material does not melt when heated in air at 300° C., which is far above the decomposition temperature of natural rubber or of any of the synthetic organic elastomers. Service over long periods of time at 150° C. does not destroy its elasticity. 

Polymer A high-molecular-weight organic compound, natural or synthetic, whose structure can be represented by a repeated small unit, the mer e.g., polyethylene, rubber, cellulose. Synthetic polymers are formed by addition or condensation polymerisation of monomers. If two or more monomers are involved, a copolymer is obtained. Some polymers are elastomers, some plastics. 

Many different synthetic elastomers are also compounded and calendered to form sheet lining materials. Examples are neoprene, Hypalon, butyl and chlor-butyl rubber. 

Just as in the manufacture of sheet natural rubber and the asphaltic sheet linings, the basic material as the sheet lining manufacturer receives it from the plantation (rubber) or from the refiner or importer (asphalt), the manufacturer of the synthetic lining materials will receive his synthetic elastomer, thermoplastic or other basic resin from the company that produces it-and will have to blend it with fillers, stabilizers, plasticizers, and other materials to make a suitable compound which will-as a lining—perform its function satisfactorily under the anticipated conditions, and for an economical length of time. The actual amount of the basic resinous material in the compound may be as low as 70% of the total weight. 

The example chosen here to illustrate this type of composite involves a polymeric phase that exhibits rubberlike elasticity. This application is of considerable practical importance since elastomers, particularly those which cannot undergo strain-induced crystallization, are generally compounded with a reinforcing filler. The two most important examples are the addition of carbon black to natural rubber and to some synthetic elastomers and silica to polysiloxane elastomers. The advantages obtained include improved abrasion resistance, tear strength, and tensile strength. Disadvantages include increases in hysteresis (and thus heat buUd-up) and compression set (permanent deformation). 

The rubber is produced by copolymerizing butadiene and st3u-ene. As with natural rubber and the other synthetic elastomers, compounding with other ingredients will improve certain properties. Continued development since World War II has improved its properties considerably over what was initially produced by either Germany or the United States. 

A number of synthetic rubbers and elastomeric materials have been developed with special characteristics that extend the overall usefulness of the elastomers for corrosion-resistant equipment. In addition, polymers of ethylene and propylene have been developed with elastomeric properties. Like natural rubber, each of these may be compounded in several ways for maximum resistance to specific chemical exposures. Natural rubber and other elastomers are frequently used in combination with brick linings for temperature conditions that are above those allowed for elastomer material alone. They have proved to be excellent membrane linings for such construction. 

Compared with other adhesives systems, the formulation of the rubber-based adhesives is very complex considerable training and practical experience is necessary before they can be successfully formulated (see Rubber-based adhesives compounding). The properties of the elastomeric adhesives depend on both the chemical type and particular grade of the natural or synthetic elastomer and on the modifying additives that may be incorporated into the adhesive formulation (tackifiers, reinforcing resins, fillers, plasticizers, curing agents, etc.). 

Fatice Sometimes called artificial rubber or a rubber substitute , fatice is made by vulcanizing with sulfur a vegetable oils such as soybean, rapeseed, or castor oil. It is used as a processing aid and extender in natural-rubber compounds and synthetic elastomers. 

Elastomers are not typically recommended for use with ozone. Polytetrafluoroethylene (PTFE) plastics are the only acceptable material. Viton or Hypalon can be used but with low life expectancy. Rubber and synthetic rubber compounds are prohibited and polyvinyl chloride (PVC) is not recommended. All elastomeric parts need to be cleaned for ozone service. 

Crude petroleum is obviously vital to the rubber industry. All of the synthetic raw elastomers and the vast majority of the rubber compounding ingredients are directly dependent on petroleum as a feedstock. It is by far the most critical natural raw material for successful rubber production and fabrication. Without crude oil, at least in the short term, there would be no rubber industry as we know it today. There would be only natural rubber for the rubber base, no rubber accelerators, no effective antioxidants, no furnace carbon black reinforcement, and so on. In the long term, however, it would be possible to manufacture organic monomers and organic rubber chemicals from other carbon sources such as agricultural products and coal tar. However, this would result in major economic dislocations and require the development of a new infrastructure. 

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