No abstract

An effective quaternary catalyst consisting of trialkyl aluminum, phosphoric acid, electron donor, and water for ring-opening polymerization of epichlorohydrin (ECH), as well as its copolymerization with ethylene oxide (EO), propylene oxide (PO), and allyl glycidyl ether (AGE) to obtain elastomers, were studied. We investigated the optimum composition for the quaternary catalyst; the character of the catalyst; the reactivity of the four alkylene oxides during homopolymerization and copolymerization; the behavior of ECH, EO, and PO during terpolymerization; and glass transition temperatures of the copolymer and terpolymers. The results showed that the nitrogencontaining electron donors are suitable as the third component, whereas oxygencontaining electron donors are not. Water as the fourth component can increase the molecular weight of the homopolymer and copolymers of ECH. According to the polymerizability of tetrahydrofuran with the quaternary catalyst and the reactivity ratios of the four alkylene oxides, the quaternary catalyst was assumed to be of a coordinated anionic type. The reactivity ratios for these four alkylene oxides were determined to be EO Ͼ PO Ͼ AGE Ͼ ECH. They were verified by terpolymerization of ECH, EO, and PO. The glass transition temperature of the terpolymer exhibits a minimum value at nearly 3:1 molar ratio of PO to EO, when the molar ratio of ECH used is constant at the beginning of terpolymerization.

Hydrogenation of carboxylic styrene-butadiene rubber latex was carried out using hydrazine and hydrogen peroxide with ferrous sulfate as a catalyst without pressurized hydrogen and an organic solvent. A mixed inhibitor was used during hydrogenation to prevent gel formation. Various hydrogenation conditions were studied. Ferrous sulfate is better than is cupric sulfate as a catalyst. The hydrogenation degree can reach over 90%. The hydrogenated product was characterized by IR and DSC. The hydrogenated products behave as a thermoplastic elastomer with excellent thermooxidation resistance, due to the absence of most double bonds and the presence of crystalline domains of polyethylene segments formed by the hydrogenation of polybutadiene segments. Ionomers were obtained by neutralization of the hydrogenated product with metallic ions and characterized by IR, DSC, and TEM. The ionomers also behave as thermoplastic elastomers with mechanical properties better than those of the hydrogenated product without neutralization, due to the existence of ionic domains besides the crystalline domains.

Hydrogenation of nitrile-butadiene rubber latex was carried out using hydrazine and hydrogen peroxide, with copper sulfate as catalyst and without pressurized hydrogen and organic solvent. A special inhibitor was used during hydrogenation to reduce gel formation. Various hydrogenation conditions were studied. The gel content of the hydrogenation product can be reduced to ϳ15%, and hydrogenation degree can reach ϳ87%. The hydrogenated product was characterized by infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. The hydrogenated product behaved as an oilresistant thermoplastic elastomer with excellent thermooxidation resistance, due to the absence of most double bonds and the presence of crystalline domains of polyethylene segments formed by hydrogenation of polybutadiene segments and nitrile groups. The higher the hydrogenation degree, the higher were the mechanical properties and thermooxidation resistance of the product. The product with a hydrogenation degree of 87% withstood thermooxidation quite well at 150°C for 65 h, maintaining ϳ98% of its tensile strength and 96% of its ultimate elongation.

Maleation of EPDM in xylene solution using dibenzoyl peroxide as initiator at the boiling point of solution was studied. Effects of amounts of dibenzoyl peroxide and maleic anhydride (MAH), reaction time and temperature, as well as the concentration of EPDM on the bond MAH content of the product were investigated. The results showed that by optimization of the maleation conditions, maleated product with high bond MAH content up to 20 wt % can be obtained without gelation. The maleated EPDM (MEPDM) was utilized in the blending of acetal copolymer and rubber such as EPDM or cis-1,4-polybutadiene. Both the impact strength and the tensile strength of the blends increased when a certain amount of MEPDM was added. Decrease of crystallinity of acetal copolymer in the blends determined by wide angle X-ray diffraction and morphology of the blends examined by scanning electron microscope demonstrated the action of MEPDM as compatibilizer.