Elastomer phase

Fig. 4. Phase arrangement in hard polymer/elastomer combinations in which the elastomer phase has been dynamically vulcanised.

Other thermoplastic elastomer combiaations, ia which the elastomer phase may or may not be cross-linked, include blends of polypropylene with nitrile (30,31), butyl (33), and natural (34) mbbers, blends of PVC with nitrile mbber (35,36), and blends of halogenated polyolefins with ethylene interpolymers (29). Collectively, thermoplastic elastomers of this type ate referred to herein as hard polymer/elastomer combinations. Some of the more important examples of the various types are shown in Table 3. 

Elastomer phase reported to be ionicaHy cross-linked (52). 

Although the elastomer phase is essentially in particulate form, the tensile strength of the blend can be increased five-fold by increasing the cross-link density from zero to that conventionally used in vulcanisation processes, whilst tension set may be reduced by over two-thirds. Since the thermoplastic polyolefin phase may be completely extracted by boiling decalin or xylene, there is apparently no covalent chemical bonding of elastomer and thermoplastic phases. 

Figure 11 Polarized microscope photographs ( x 800) (A) PBT-TLCP-elastomer blend (60 25 15 wt ratio). Dark phase is the TLCP phase. (B) Nylon 6-TLCP-elastomer blend (60 25 15 wt ratio). Dark phase is the TLCP phase and large white one is the elastomer phase. Source Ref. 56.

The blends are cured with a sulphur-sulphonamide zinc stearate mixture so that the elastomer phase is hardened and then microtomed. 

Thermoplastic elastomers (TPE), 9 565-566, 24 695-720 applications for, 24 709-717 based on block copolymers, 24 697t based on graft copolymers, ionomers, and structures with core-shell morphologies, 24 699 based on hard polymer/elastomer combinations, 24 699t based on silicone rubber blends, 24 700 commercial production of, 24 705-708 economic aspects of, 24 708-709 elastomer phase in, 24 703 glass-transition and crystal melting temperatures of, 24 702t hard phase in, 24 703-704 health and safety factors related to, 24 717-718... 

The type of rubber chosen depends on the desired mechanical properties and on the end use. If, for example, excellent outdoor weatherability is required, the use if saturated rubbers as elastomer phase is possible. 

The impact resistance of the SIN plastics increased with elastomer content and polyester content of the elastomer phase. 

Dynamical mechanical spectroscopy and Izod impact results suggest that the glass transition temperature of the elastomer phase constitutes the most critical parameter in achieving impact resistance in these materials. 

The modulus, elongation to break, ultimate strength, and toughness of the straight castor oil elastomers increase with increasing amounts of TDI employed as crosslinker. A similar trend was observed in the elastomeric SIN s (40% elastomer content) in which the elastomer phase was continuous. 

Processing oil is a well-known additive for rubbers and is commonly employed in PP/EPDM TPVs [10-12]. It lowers the hardness and improves the processability. The oil, in most cases paraffinic oil, can be considered as a low molecular weight olefin. The difference in polarity between the three components is small, and the oil is present in both the PP and in the elastomer phases [67]. In order to understand the mechanical and the rheological properties of olefinic thermoplastic elastomers (OTPEs), the concentration of oil in each phase must be known. 

Interfacial Bonding between Different Elastomer Phases... 

Evidence of Interfacial Bonding. In these experiments compounded blends were composed of two elastomer phases that were first mixed with curative ingredients before blending in various ratios. This procedure was adapted to ensure proper initial distribution of the ingredients between the two phases. Blending was accomplished, with one exception, by mill mixing on a small laboratory two-roll mill. After blending, cured specimens in the form of small 0.025-inch thick pads were swollen in a common solvent to observe the over-all state of network... 

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