Vulcanizate tensile strength copolymers

Clay hllers were surface modihed with TMPTA or triethoxyvinyl silane (TEVS) followed by EB irradiation by Ray and Bhowmick [394]. Both the untreated and treated fillers were incorporated in an ethylene-octene copolymer. Mechanical, dynamic mechanical, and rheological properties of the EB-cured unfilled and filled composites were studied and a significant improvement in tensile strength, elongation at break, modulus, and tear strength was observed in the case of surface-treated clay-filled vulcanizates. Dynamic mechanical studies conducted on these systems support the above findings. 

Hence, it was of interest to investigate any possible effects of the Ty and modulus of polymeric fillers on the tensile strength of vulcanizates. For this purpose a series of polymeric fillers was prepared by emulsion polymerization, using monomers or mixtures of monomers designed to yield polymers or copolymers of varying Tg and modulus. The experimental details of the polymerization will be described in a forthcoming publication. The characteristics of these polymeric fillers are given in Table I. 

Copolymers containing up to 10 mole% 0-pinene are rubbery (Tg -53°) and can be sulfur vulcanized. The non-filled vulcanizates are very soft rubbers (e.g., 300% modulus 7.7 kg/cm or 110 psi) with high ultimate tensile strength (eg, tensile strength 246 kg/cm or 3,500 psi). The high tensile strength is attributed to stress induced crystallization. 

New diene copolymers can be expected. Butadiene-acrylic acid and butadiene-methylvinylp3mdine copolymers have been reported. One of the former copolymers, compounded with zinc oxide, formed a vulcanizate with a tensile strength of over 8,000 psi, the highest on record. The latter copol3rmer has been quaternized with active halogen compounds to form a new type of elastomeric material. ... 

Some properties of sodium and zinc vulcanizates are compared with those of the acid precursor in Table 5.16. High tensile strength is a characteristic of ionic vulcanizates. As a comparison, a standard polybutadiene elastomer vulcanized with sulfur gives a strength of 1.9-5.8 MPa (275-841 Ibf/in. ), whereas an equivalent copolymer containing 1.5 mole% methacrylic acid, and vulcanized with... 

The arrangement of the blocks is important high-tensile-strength materials, with elastomeric properties similar to a filler-reinforced vulcanizate, are obtained only when the copolymer contains two or more polystyrene (S) blocks per molecule. Thus, copolymers with the structure S.B. or B.S.B. (who B is a polybutadiene block) are as brittle as polystyrene, but S.B.S and S.B.S.B copolymCTS are much tougher. At ambient temperatures these behave like conventional cross-linked rubbers, but they have the additional advantage that their thermal behavior is reproducible. 

Fig. 10. The influence of polystyrene on the tensile strength of the butadiene-acrylonitrile copolymer vulcanizates.

Trifluoronitrosomethane-tetrafluoroethylene copolymer has good thermal stability. The copolymer does not bum but decomposition into gaseous products begins at about 200°C. The glass transition temperature of the copolymer is -54 C and vulcanizates remain serviceable down to about -40°C. A limitation of the vulcanizates is their low tensile strength, although silica effects some reinforcement. 

Because of the regular structure both the raw polymer and the vulcanizates of these rubbers are claimed to be capable of crystallization (this implying some tactic homogeneity of the acrylonitrile in addition) so that the tensile strength of both cured and uncured stocks is higher than for conventional nitrile rubbers. Resistance to cut-growth and to creep tear are also said to be superior. Properties less dependent on structural regularity, such as oil resistance and low temperature properties are similar to those of free-radically produced random copolymers. 

TMO-AGE Elastomers. The sulfur vulcanizate of the 96-4 TMO-AGE copolymer had high tensile, modulus, and tear strength at 23 C. at a good elongation level (Table V). The hot tensile properties at 100 C. are somewhat lower but still good. Crystallinity and/or crystallization on stretching could enhance tensile properties at 23°C. apparently this is not the case, since the hot tensile results, which could not involve crystallinity... 

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