Vulcanized elastomer

Fig. 1. Retention of elongation of vulcanized elastomers at 150°C. A, nitrile mbber, NBR B, ethylene—propylene—diene mbber, EPDM C, acryflc...

Subsequently, much improved thermoplastic polyolefin rubbers were obtained by invoking a technique known as dynamic vulcanisation. This process has been defined (Coran, 1987) as the process of vulcanizing elastomer during its intimate melt-mixing with a non-vulcanizing thermoplastic polymer. Small elastomer droplets are vulcanized to give a particulate... 

B. Properties of Conventionally Vulcanized Elastomer-Plastic Blends... 

Isayev, A.I., Continuous ultrasonic devulcanization of vulcanized elastomers, US Patent, 5,258, 413, 1993. 

These products find use in specialty applications requiring better thermal stability than available in the sulfur vulcanized elastomers. Other processes are also used to crosslink polydiene rubbers (Secs. 9-2c and 9-2d). 

The diffusion coefficient D is always related inversely to the crosslink density of vulcanized elastomers. When Z)is extrapolated to zero concentration of the diffusate, it is related to the weight of the principal section of the elastomer, i.e., the weight of the segments between crosslinks. 

Cured polymers of butadiene with low cross-link density do not tend to cold flow and are useful elastomers. These vulcanized elastomers crystallize when stretched, but when the stress is removed, the restoring force is largely entropy and most of the crystals melt and the chains return to the random conformation.The tensile strength is increased dramatically when large amounts of carbon black or amorphous silica are added. 

Identical to chemically cross-linked (vulcanized) elastomers, the modulus of radiation cured gum elastomers depends on the concentration of elastically effective network strands and temperature. ... 

Thermoplastic elastomers (TPEs) are either block copolymers (SBS, SEES, SEPS, TPU, COPA, COPE) or blends, such as TPO (elastomer/hard thermoplastic, also referred to as thermoplastic olefin) and TPV (fhermoplastic vul-canizafe, blend of a vulcanized elastomer and a hard fhermoplastic). These types represent the majority of fhe TPEs other types are either specialty or small-volume materials. 

Early investigations of crosslinked polymeric materials observed line width changes with cure. An increase in the line width is observed in vulcanized elastomers at room temperature, compared with the unvulcanized samples 13). The effect of vulcanization on line widths of butadiene-styrene copolymers in a temperature range near the glass transition (Tg), was interpreted in terms of the formation of cooperative domains, which lead to larger linewidths (Av)14). Both, an increase in Av and shift of the transition range to higher temperatures due to the restriction of molecular mobility... 

Andreis M, Liu J, Koenig JL (submitted to J. Polym. Sci., Polym. Phys. Edn. for publ.) Solid state carbon-13 NMR studies of vulcanized elastomers. V. Observation of new structures in sulfur vulcanized natural rubber... 

Many studies of vulcanized elastomer blends have revealed discontinuities in physical property trends attributable to poor interfacial bonding. Recently Rehner and Wei (5) have observed discontinuities in the swelling of blended crosslinked networks swollen in a common solvent. This departure from an averaged swelling behavior, based upon compositional ratios and the swelling behavior of the two homophases, re-... 

Bonding of already vulcanized elastomers to themselves and to other materials is generally completed by using a flexible thermosetting adhesive such as epoxy-polyamide or... 

The possibility of employing block copolymers as materials that might possess desirable properties was originally considered by Mark In the first period the effort in preparing block copolymers was directed to radical polymerization and it was only in 1956 that Szwarc obtained well-defined block copolymers by anionic polymerization . In block copolymers, the incompatibility between polymeric chains becomes an advantage a phase separation of the blocks occurs leading to the formation of microdomains which are responsible for the ecific properties of block copolymers. For instance, the presence in a molecule of an elastomeric block linked by its ends to thermoplastic blocks generates a polymer in which reversible physical multifunctional cross-links allow the behaviour of conventional vulcanized elastomers at room temperature, but the material remains easily moldable at elevated temperature just as normal thermoplastic resins ° ... 

Vulcanization is an industrial process applied to various polymers from the class of unsaturated polyhydrocarbons. The major practical use of vulcanized elastomers is the tire industry. Tires are made from various polymer blends, including natural rubber, typically between 20 and 50%. The other polymers used in various blends that can be vulcanized include copolymers such as poly(styrene-co-1,3-butadiene) or SBR, poly(acrylonitrile-co-1,3-butadiene-co-styrene) or ABS, poly(isobutylene-co-isoprene), poly(ethylene-co-propylene-co-1,4-hexadiene, etc. 

Methyl Niclate . [R.T. Vanderbilt] Nidrel dimediyiditidocarbainate antioxidant for epchloiohydrin and peroxide vulcanized elastomers. 

The quantity of rubber insoubilized by carbon black due to adsorption from the bulk is known as bound rubber. It has long been assumed that the mechanism by which bound rubber is formed is also responsible for reinforcement in the vulcanized elastomer. This section deals with several aspects of the formation of bound rubber and its relationship to reinforcement. 

The blends of EPDM terpolymers and isotactic PP with curing agents, such as peroxide, phenol resins, and sulfur, are termed as thermoplastic vulcanized elastomer (TPV) since the rubber domains are vulcanized. Polyolefin copolymers, such as random copolymer of propylene with ethylene, copolymers of other olefins, elastomeric PP, and elastomeric PE, are developed with recent advances of... 

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