Peter E Wei

Heterogeneity and Crosslinking of Elastomer Blends. Investigations of Chlorobutyl with Highly Unsaturated Elastomers

Abstract Literature on the fundamental physios and chemistry of elastomers blends is limited, even though blends are employed commercially. Past research on individual elastomers is inadequate for a good understanding of blends. Properties of elastomers blends, unlike those of plastic blends, depend on vulcanization chemistry. The general problem is therefore one of understanding the nature and properties of elastomer blends in which complex chemical reactions have been superimposed on a complex physical state. The present paper is a preliminary examination of both of these aspects.

Reactions of Isoparaffins with Sulfur and DI-t-Butyl Peroxide

Abstract The role which sulfur plays in the peroxide vulcanization of polyisoparaffins has been investigated. The problem was studied by using a system in which 2,4dimethylpentane is a model for the polyisoparaffin chain. Two alternative reaction mechanisms are proposed. Work with the model system shows that polysulfides formed from the isoparaffin are the dominant products. By analogy it is inferred that polysulfide linkages join the polyisoparaffin chains, preferably at what were formerly tertiary hydrogen sites. Nearly all of the high boiling products are disulfides and, or, polysulfides, and these total at least a 28 mole per cent yield based on peroxide charged. Thus, it is indicated that sulfur plays a major role, and does not simply prevent minor side reactions. Study of the gaseous reaction products indicates that sulfur does not alter the course of the initiation step. A reaction mechanism is proposed which is consistent with literature and with our experimental work.

New Vulcanizing Agents for Ethylene Propylene Elastomers. III

Abstract Di(trichloromethyl) sulfone and dichloromethylene-bis(trichloromethyl sulfone) can vulcanize saturated hydrocarbon elastomers like EPR when used in combination with sulfur. The activity is enhanced by the presence of certain metal oxides. These agents are also effective in some other elastomers, and in their blends with EPR. They are also effective in combinations with octachlorocyclopentene, and with cumyl peroxide. Synergistic effects are observed in the tensile properties of such systems. Dichloromethylene-bis(trichloromethyl sulfone) is so active in EPR that it gives rise to scorch. Efforts to alleviate this drawback by the use of sulfur donor compounds or retarders, and by other means, have not yet proved to be successful. Di (trichloromethyl) sulfone appears to be quite tolerable as far as scorch is concerned, but its lachrymatory nature might be a disadvantage in large-scale non-vented processing operations. Chemical studies carried out with model systems indicate that perchloromethyl sulf...

Readily Curable Chlorinated Poly-α-Olefins and Ethylene-α-Olefin Copolymers

Abstract Chlorinated polyolefins have been prepared which are readily curable at 287° F at low chlorine contents. Their preparation depends primarily on using a chlorination solvent, generally an aromatic compound, which introduces both reactive chlorine and unsaturation. A process has been developed wherein ethylene propylene copolymers are first prepared and then chlorinated in the same aromatic solvent. Chlorinated copolymers have been cured with a variety of formulations which take advantage of the lability of chlorine atoms or of unsaturation, or of both. Properties of vulcanizates of chlorinated ethylene propylene copolymers are described.

New Vulcanizing Systems for Ethylene-Propylene Elastomers

Abstract The absence of chemical functionality in ethylene-propylene elastomers precludes crosslinking with conventional rubber vulcanizing agents. It is known that such elastomers can be vulcanized with combinations of sulfur and certain organic peroxides, but the resulting vulcanizates leave something to be desired from the standpoint of tear strength, odor, and peroxide cost. A chemical study of the reaction between isoparaffins, sulfur, and organic peroxides gave results showing that some important alterations must be made of previous views that have been advanced for the vulcanization of saturated hydrocarbon elastomers by peroxides alone. A new reaction scheme is briefly reviewed. In the course of this study, three new classes of substances have been discovered to be effective vulcanizing agents for ethylene-propylene elastomers, and for other rubbers also. The outstanding characteristics which these new agents produce in ethylene-propylene elastomer vulcanizates are excellent tear strength and no o...