Vulcanizate studies

FIGURE 12.4 Morphology of rubber vulcanizates studied A, B - NBR-W-REF C, D -NBR-W-48 magnification 5000x. 

Mechanical properties of the vulcanizates studied, containing virgin and plasma modified fillers are presented in Figs. 12.6a-12.6f. 

Mechanical properties of the vulcanizates studied were determined with a Zwick 1435 universal mechanical testing machine (Germany). Tests were carried out on dumbbell shape, 1.5 mm thick and 4 mm width specimens. 

Wire and cable insulation based on vulcanizates of PZ has also been studied. Again, low fire risk was the target property, and this was achieved. The need to vulcanize the coating, somewhat modest tensile properties, tensile strength of 5.2 to 12.2 MPa (760 to 1770 psi), and high dielectric constant (4—5 at 10,000 Hz) limited interest in this appHcation (19). 

Fluoroelastomers Novikova et al. [32] reported unproved physico-mechanical properties of fluoro mbbers by reinforcement with chopped polyamide fibers. Other fiber reinforcements are covered by Grinblat et al. [33]. Watson and Francis [34] described the use of aramid (Kevlar) as short fiber reinforcement for vulcanized fluoroelastomer along with polychloroprene mbber and a co-polyester TPE in terms of improvement in the wear properties of the composites. Rubber diaphragms, made up of fluorosilicone mbbers, can be reinforced using aramid fiber in order to impart better mechanical properties to the composite, though surface modification of the fiber is needed to improve the adhesion between fluorosUicone mbber and the fiber [35]. Bhattacharya et al. [36] studied the crack growth resistance of fluoroelastomer vulcanizates filled with Kevlar fiber. 

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. 

The effect of palm oil fatty acid additive (POEA) on curing characteristics and vulcanizate properties of sdica-filled NR compounds was studied by Ismail [30]. The incorporation of POEA improved the cure rate and state of cure of the compounds. Compared to the control, the incorporation of POEA not only enhanced the vulcanizate properties but also improved the reversion resistance of the silica-filled NR compounds. 

The hydrogenation of unsaturated polymers and copolymers in the presence of a catalyst offers a potentially useful method for improving and optimizing the mechanical and chemical resistance properties of diene type polymers and copolymers. Several studies have been published describing results of physical and chemical testing of saturated diene polymers such as polybutadiene and nitrile-butadiene rubber (1-5). These reports indicate that one of the ways to overcome the weaknesses of diene polymers, especially nitrile-butadiene rubber vulcanizate, is by the hydrogenation of carbon-carbon double bonds without the transformation of other functional unsaturation such as nitrile or styrene. 

High MW fraction in EPDM ought to contribute favorably to the vulcanizate tensile properties ( ). The following preliminary observations were gathered to examine whether difference in. tensile strength of samples prepared with various catalysts studied was due primarily to the difference in MWD of the terpolymers. ... 

On the other hand, silicones are used in organic composites. The application of alloys composed of the fully cured silicone rubber particles in a continuous thermoplastic phase, called thermoplastic silicone vulcanizate, which offers high-performance materials, has been reported.506,507 Functionalized POSS was not only co-polymerized, but also blended with poly(methylmethacrylate) to study the effect of silsesquioxanes on the thermal stability of thermoplastics.508... 

R. Hulst, R. M. Seyger, J. P. M. van Duynhoven, L. van der Does, J. W. M. Noordermeer and A. Bantjes, Vulcanization of butadiene rubber by means of cyclic disulfides. 2. A 2D solid state HRMAS NMR study on cross-link structures in BR vulcanizates, Macromolecules,... 

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