Elastomers natural rubber

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. 

Elastomer Natural rubber Halobutyl rubber Dimethylpolysiloxane polymer EPDM... 

Elastomers Natural Rubber, Kostin V SBR, Si licones, Polybutadiene... 

A number of manufactured products comprising thermoplastics (polyethylene, polyvinylchloride, polyamides,. ..) or elastomers (natural rubber, nitrile rubber, ethylene propylene rubber, silicones) are processed by cross-linking to improve their performances in insulated electric wires and cables, multilayered films for cooking pouches, shape memory tubes, pressure resistant water pipes, expandable foams, automotive parts exposed to motor... 

Elastomer Natural rubber Butyl rubber Chlorinated Butyl Rubber Nitrile rubber Silicone rubber Hypalon Chloroprene Viton EPDM EVA... 

The choice of elastomer has the greatest effect on a formulation. The most common elastomers that can be used for closures for injectable products are given in Table 12.5. Of these elastomers, natural rubber, synthetic polyisoprene, butyl, chlorobutyl and bromobutyl rubber are typically used for the manufacture of rubber closures and stoppers used in the packaging and administration of parenterals. 

Cross-Hnked elastomers natural rubber, natural rubber latex (NR)... 

Rubber is the most important of all elastomers. Natural rubber is obtained from the bark of the rubber tree and has been used by humans for many centuries. It is a polymer with repeating units of isoprene. In 1823, rubber was vulcanized with sulfur whilst heated and this process made it to become the valuable material it is today. In this process, sulfur chain fragments attack the rubber polymer chains, which leads to cross-linking. Most of the rubber used in the world is a synthetic variety called styrene-butadiene rubber. 

Since the density of plastics highly depends on the presence of fillers or other additives, this property is far from being a characteristic feature. Unfilled polyolefines (polyethylene and polypropylene), a number of elastomers (natural rubber and silicone rubber), and foamed plastics come within the rare category of polymers which float on water. Some fluoropolymers exhibit a density around or greater than 2 g/cvo (see also Table 3.3). 

FIGURE 10.15 Fracture energy, G, for a strain-crystallizing elastomer, natural rubber, as a function of temperature, T, and rate of tearing, R. (From Greensmith and Thomas (1955).)... 

Cold water preserves natural rubber, but if exposed to the air, particularly in sunlight, rubber tends to become hard and brittle. It has only fair resistance to ozone. Unlike the s)mthetic elastomers, natural rubber softens and reverts with aging to sunlight. In general, it has relatively poor weathering and aging properties. 

Thermoplasts and thermosets Synthetic elastomers Natural rubber Synthetic fibers Natural fibers and fibers from naturally occurring raw materials Cotton... 

Diene Types The diene elastomers are based on polymers prepared from butadiene, isoprene, their derivatives and copolymers. The oldest elastomer, natural rubber (polyisoprene), is in this class (see Section 9.2). Polybutadiene, polychloroprene, styrene-butadiene rubber (SBR), and acrylonitrile-butadiene rubber (NBR) are also in this class. 

Pressure-sensitive adhesives form physical bonds with other materials upon brief contact and with light pressure. Examples include self-stick stamps, packaging tape, double-sided tapes, paper labels, and the ubiquitous Post-iE notes. Bond formation results from the polymeric material being able to flow under light pressure, thereby establishing good contact area with the substrate. The debonding step involves deformation of the polymeric material under stress (see Section 12.8.3), followed by separation from the substrate. The adhesives most often involve triblock copolymers such as poly(styrene-h/ock-isoprene-h/ock-styrene) or poly(styrene-Wodc-butadiene-h/ock-styrene), SBR elastomers, natural rubber, or acrylic copolymers (92). 

Parel elastomer, natural rubber, and neoprene, compounded with standard recommended formulas for each, were heat aged in a 125 C. forced draft oven. Figure 3 is a plot of the change in tensile strength and hardness of the vulcanized Parel and neoprene elastomers. Neoprene maintained its properties for 3 days, but after a week at 125 C., it was quite hard and brittle. Results with natural rubber are not included in the figure because it failed so quickly at 125 C. It was seriously deteriorated in about 3 days at 100 C. 

Medical tapes are the oldest application of pressure-sensitive tapes [203]. Major progress towards skin compatibility was made by introduction of zinc oxide into the rubber-based PSAs [282]. With the development of polyisoprene, polyisobutylene, and other synthetic elastomers, natural rubber was replaced to a certain extent in medical products by synthetic rubbers. These were followed by the styrenic block copolymers [211, pp. 317-373]. 

Most pressure-sensitive masscoats contain a blend of elastomers—natural rubber, reclaim and SBR—with tackifiers of low or medium molecular weight, antioxidants, etc. These are applied to the web-tape or label backing from solutions but the newer thermoplastic elastomers —block copolymers of styrene with is-oprene or butadiene—can be applied from melt. Where excellent color and resistance to light and oxidation are needed, the higher priced acrylic ester copolymers are preferred. Polyisobutylene, also resistant to ultraviolet degradation, is utilized for removable labels. 

As with most elastomers, natural rubber can be readily bonded with cyanoacrylates although in these trials [2] the adhesion achieved with the toughened cyanoacrylates was relatively low (Table 4.7). 

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