Elastomer blends copolymers

Another area of recent interest is covulcanization in block copolymers, thermoplastic rubbers, and elasto-plastic blends by developing an interpenetrating network (IPN). A classical example for IPN formation is in polyurethane elastomer blended acrylic copolymers [7]. 

Compatibilization along with dynamic vulcanization techniques have been used in thermoplastic elastomer blends of poly(butylene terephthalate) and ethylene propylene diene rubber by Moffett and Dekkers [28]. In situ formation of graft copolymer can be obtained by the use of suitably functionalized rubbers. By the usage of conventional vulcanizing agents for EPDM, the dynamic vulcanization of the blend can be achieved. The optimum effect of compatibilization along with dynamic vulcanization can be obtained only when the compatibilization is done before the rubber phase is dispersed. 

Currently, important TPE s include blends of semicrystalline thermoplastic polyolefins such as propylene copolymers, with ethylene-propylene terepolymer elastomer. Block copolymers of styrene with other monomers such as butadiene, isoprene, and ethylene or ethylene/propy-lene are the most widely used TPE s. Styrene-butadiene-styrene (SBS) accounted for 70% of global styrene block copolymers (SBC). Currently, global capacity of SBC is approximately 1.1 million tons. Polyurethane thermoplastic elastomers are relatively more expensive then other TPE s. However, they are noted for their flexibility, strength, toughness, and abrasion and chemical resistance. Blends of polyvinyl chloride with elastomers such as butyl are widely used in Japan. ... 

Polyamide/rubber blends, 20 361 Polyamide block copolymers, 24 704, 708 Polyamide composite membranes, 21 633 Polyamide-elastomer block copolymers, 24 698... 

S—EB—S (compounds) polyurethane/elastomer block copolymers polyester/elastomer block copolymers polyamide/elastomer block copolymers polyetherimide/polysiloxane block copolymers polypropylene/EPDM or EPR blends polypropylene/EPDM dynamic vulcanizates polypropylene/butyl rubber dynamic vulcanizates polypropylene/natural rubber dynamic vulcanizates polypropylene/nitrile rubber dynamic vulcanizates PVC/ nitrile rubber blends... 

In this paper, we wish to report two different types of elastomer blends, ethylene-propylene-diene terpolymer/polyacety-lene and styrene-diene triblock copolymer/polyacetylene, in the hope that the stability of polyacetylene might be improved by... 

Morphology in multiphase systems As shown SemicrystaUine copolymers, blends, block copolymers Lamellae, width Lamellae, length Elastomer blends, major dimension 50-150 A 0.01-2 pm 0.5-10 pm (2-4,9,10)... 

Uses Lt. stabilizer for polyolefins, polyolefin-elastomer blends, fiber, tape, film, articles, food-contact propylene polymers/copolymers... 

Angier and Watson [A7, A9] found that graft copolymers could be prepared by masticating elastomer blends in the absence of oxygen. The systems studied included natural rubber/polychloroprene, natural rubber/ butadiene-styrene copolymer, and polychloroprene/butadience-styrene copolymer. The mechanism hypothesized was... 

The EP thermoplastic elastomers are distinguished from the crossUnked analogues, which are not thermoplastics since reforming is impossible. A very important thermoplastic elastomer is comprised of a blend of an EP copolymer with an ethylene-propylene-diene (EPDM) terpolymer. This latter material is, of course, a crosslinkable thermoset however, these materials can be processed as thermoplastics if the crosslinkable component is present at low enough concentration to be present as an isolated phase. Melt-processing causes the formation of chemical bonds within the isolated rubber phase, a process called dynamic vulcanization. A commercial example of this type of material is Santoprene [4] manufactured by Advanced Elastomer Systems. Other blends of noncrosslinkable TPEs with crosslinkable materials are used commercially. These materials are classified as elastomer blends and are the subject of Chapter 12. 

In contrast to the rigid TPOs described above, low-modulus/flexible grades of TPO blends are also produced commercially. In flexible TPOs, the rubber content can be as high as 60 %, and in some cases, the dispersed rubber may also be partially cross-linked during the mixing without losing the thermoplastic character of the matrix. However, the latter type of dynamically vulcanized elastomeric alloys or thermoplastic vulcanizate rubbers (TPVs) are considered as a separate class of elastomeric materials and hence will be discussed under elastomer blends. On the other hand, the soft TPO blends discussed here contain a low-modulus olefln copolymer elastomer as the major component with some polypropylene added to impart melt processability. 

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... 

Before reviewing in detail the fundamental aspects of elastomer blends, it would be appropriate to first review the basic principles of polymer science. Polymers fall into three basic classes plastics, fibers, and elastomers. Elastomers are generally unsaturated (though can be saturated as in the case of ethylene-propylene copolymers or polyisobutylene) and operate above their glass transition temperature (Tg). The International Institute of Synthetic Rubber Producers has prepared a list of abbreviations for all elastomers [3], For example, BR denotes polybutadiene, IRis synthetic polyisoprene, and NBR is acrylonitrile-butadiene rubber (Table 4.1). There are also several definitions that merit discussion. The glass transition temperature (Tg) defines the temperature at which an elastomer undergoes a transition from a rubbery to a glassy state at the molecular level. This transition is due to a cessation of molecular motion as temperature drops. An increase in the Tg, also known as the second-order transition temperature, leads to an increase in compound hysteretic properties, and in tires to an improvement in tire traction... 

As a result of the poly addition of the DBDI based materials by the one shot synthesis in melt, it obtained opaque solid elastomer blends consisting of two copolymers, one of which was soluble in DMF (87%), while the other was insoluble in DMF (13%), (PUioo — Table 3.11). 

Polypropylene homopolymer, polypropylene copolymer, and a polypropylene elastomer blend (TPO) were melt compounded with 2.0,4.0, and 6.0 wt% additive. Additional tests with additive levels of 0.5,1.0 wt, and 1.5 wt% were made with Struktol TR-016. HiMod-360 mica was used at 30 wt% levels in all formulations, and there was a constant 0.2 wt% level of a stabilizer package in each compound. The maleic anhydride-modified polypropylene most effective in increasing performance properties was Unite MP-1000, but many other similar products made by a variety of companies performed nearly as well. To select the very best product, one must consider the relative costs of such additives and required use levels. 

Uniroyal, Inc. see W. K. Fischer), Dynamically Partially Cured Thermoplastic Blend of Monoolefin Copolymer Rubber and Polyolefin Plastic, Br. Pat. 1,380,884 (1975). Dynamic partial cure of EPDM or EPM. Thermoplastic elastomers. Blend with polyethylene or polypropylene. Simultaneous blending and semicuring. 

In practice, the existence of both UCST and LCST has been established for polymer-solvent systems. About 10 years ago, Schmitt discussed UCST, LCST and combined UCST and LCST behavior in blends of poly(methyl methacrylate) with poly(styrene-co-acrylonitrile) (PMMA-PSAN), Ueda and Karasz reported the existence of UCST in chlorinated polyethylene (CPE) blends using DSC, Inoue found that elastomer blends of cis-l,4-polybutadiene and poly(styrene-co-butadiene) exhibit both UCST and LCST behavior and Cong et al. (72) observed that blends of polystyrene and carboxylated poly(2,6-dimethyl-l,4-phenylene oxide) copolymers with a degree of carboxylation between molar fraction 8% and 10% exhibit both UCST and LCST behavior. They used DSC to establish the phase diagram. 

Blends of NR and ethylene-vinyl acetate copolymer (EVA) (physical blends and statically vulcanized) combine the good elastomeric and mechanical properties of NR with the excellent ageing and flex crack resistance of EVA. Blends of NR/EVA copolymer are becoming an important rubber/thermoplastic elastomer blend. Applications of these materials can be found in fields where... 

Commodity resins. Outside the range of phase co-continuity the PO/PS blends need to be compatibilized. There are several methods of compatibilization out of which the addition of styrene-elastomer block copolymers and reactive radical co-grafting are most conunon. For example, PCW comprising 55-75 wt% PO, 5-25 wt% PS, 5-15 wt% PVC, and 0-10 wt% of other thermoplastics, was compatibilized with 3-20 wt% SB, and stabilized by adding 0.1 -0.5 wt% of pentaerythritol ester and tris(2,4-di-tert-butyl phenyl) phosphite at a ratio of 5 1 to 1 5. The recycled mixtures showed good long-term performance [8]. 

Other elastomer blends of commercial utility have been cited in the literature [96-98]. Polyolefin blends have been utilized in many forms to achieve modifications yielding environmental stress rupture resistance and to improve impact strength, flexibility, and filler acceptance [99,100]. The addition of ethylene-propylene rubber (EPR) or blends of EPR and high-density PE to PP has been specifically utilized for improving the low-temperature impact strength [101]. Low-modulus materials can be produced from EPR-PP blends containing more than 50% of EPR. These products include those under the trade names TPR, Somel, and Telcar [102-105]. Addition of rubber inclusion has been shown to yield definite improvements in the environmental stress rupture resistance [106]. Other examples of commercial rubber-based blends are impact-PS, ABS and bisphenol A polycarbonate blends and polysulfone blends made of a block copolymer of polysulfone and nylon 6 [107]. 

The topics presented here are a subset of self-organization and pattern formation processes, which are also seen in various other settings such as evaporation, condensation, elastic instabilities in various materials including elastomers, block copolymers, blends, and liquid crystals. An interested reader is advised to consult some excellent review papers on each of the themes, some of which are cited in the reference section. 

Kai ger-Kocsis J and Kiss L (1987) Dynamic mechanical properties and morphology of polypropylene block copolymers and polypropylene/elastomer blends, Polym Eng Sci 27 254-262. 

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