Thermoplastic Vulcanized Elastomers

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... 

The effect of the injection molding process conditions (melt and mold temperatures, holding/packing pressure and injection velocity) over the adhesion resistance of two overmolded materials was studied. The materials used were a Thermoplastic Vulcanized Elastomer (TPV) (Santoprene 8211-55) and a Polypropylene (PP) (Moplen HP501H). The measurement of the adhesion resistance was done by Tensile Test and it was observed that the melt and mold temperature are the parameters that affect in greater degree the adhesion resistance. 

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... 

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. 

Chorvath I et al. (2001) Vulcanized thermoplastic silicone elastomers from nylon resins and polysiloxanes. WO Patent 2001072903... 

TPEs are blends of various amorphous rubbers such as ethylene-propylene and of polyolefin semicrystalline plastics such as PP. They are part of the family of TP olefins (TPOs). TPOs are mechanical blends consisting of a hard plastic and softer rubber. They are considered different from blends that are dynamically thermoplastic vulcanized (TPV) a process in which the elastomer phase is cured during mixing of the polymers.84 94... 

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 ° ... 

Dynamically vulcanized blends Dynamically vulcanized blends are produced by melt mixing an elastomer phase with a thermoplastic (the elastomer being the major component) and then curing the elastomer during melt mixing. The resulting blend comprises the thermoplastic resin filled with high concentration of rubber particles well bonded to the matrix. Examples include EPDM/PP (Santo-... 

A. Y. Coran and R. P. Patel, Thermoplastic elastomers based on dynamically vulcanized elastomer— Thermoplastic blends, in Thermoplastic Elastomer, G. Holden, N. R. Legge, R. Quirk, and H. E. Schroeder (eds.), Hauser, New York, 1996, p. 153, Chapter 7. 

In contrast to thermoplastic materials, crosslinked (vulcanized) elastomer products cannot be remelted. This puts narrow limits on material recycling or reuse. The case is different with the recycling and reuse of tires, the main elastomeric product. 

Biomedical elastomers can be classified as to whether they are thermoplastic or thermosetting in nature. Thermoplastic biomedical elastomers are gaining in commercial importance and in some cases replacing traditionally used vulcanized versions. Thermosetting elastomers are irreversibly crosslinked and have had the longest history of medical use. Both groups will be described citing representative medical elastomers that are either commercially available or that may replace elastomers that have been recently withdrawn from the market. 

SBCs are characterized by their molecular architecture, which has a hard thermoplastic segment and a soft elastomeric segment that alternate in many different ways. Figure 9.3 shows a typical molecular architecture of SBS rubber. In a very crude sense, SBCs have strength properties equivalent to vulcanized elastomer systems without vulcanization. 

Thermoplastic Dynamically Vulcanized Elastomer Blends (TPV Blends)... 

Dynamically vulcanized, elastomeric thermoplastic alloys or TPVs display properties as good as or even better than the block copolymers, viz., a high degree of rubber elasticity yet good melt processability. The main advantages of the thermoplastic vulcanizate elastomer blends over the uncured thermoplastic/elasto-mer blends are... 

A-B-A n. Thermoplastic elastomers. Three-block thermoplastic polymer elastomer, high-strength rubber, no vulcanization, completely soluble, two glass and two glass transition temperatures, i.e., styrene and butadiene. 

Montell s in-reactor Catalloy ( catalytic alloy ) polymerization process alloys propylene with comonomers, such as EPR and EPDM, yielding very soft, very hard, and rigid plastics, impact grades or elastomeric TPOs, depending on the EPR or EPDM % content. The term olefinic for thermoplastic olefinic elastomers is arguable, because of the generic definition of olefinic. TPVs are composed of a continuous thermoplastic polypropylene phase and a discontinuous vulcanized rubber phase, usually EPDM, EPR, nitrile rubber, or butyl rubber. 

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