Conclusion
tert-Butylperoxy isopropyl carbonate (BPIC) has recently been developed as a ne\v catalyst for the polymerization of a variety of monomers and the crosslinking of elastomers. T h e available commercial product (90 to 957, assay) is a liquid that i b relatively stable under ordinary storage and handling conditions. 'l'he main products of thermal decomposition are acetone: trrt-butyl alcohol, and carbon dioxide. T h e half life for 0.2.44 solutions in benzene characterizes BPIC a:: a n initiator active in a n intermediate temperature range. It is particularly effective foi the free radical polymerization of eth)-lene.
(3) navies. A. G., "Organic Peroxides," pp. 65, 67, Butterworths; London, 1961. (4) Da\ ies. A. G.. Hunter, K. J., J . Chern. SOC.1953, 1808. ( 5 ) Doehnert: D. F.: ihlageli. 0. L., .tlod. Plastics 36 (6), 142 11959,. (6)' Harrison, .J. B., Mageli. 0. L. (to LVallace 8: Tiernan), U. S. Patent 3,117,166 (.Jan. 7. 1964). (7) Ha\vkins, E. G.. "Organic Peroxides." pp. 329-31, Van Nostrand, New York. 1961. (8) Mageli. 0. L.. Stengel. S. D.: Doehnert, D. F.; '2lod. Plastzcs 36 (7). 135 (1959). (9) Mair. I>
literature Cited
I
(1) Dannenberg. E. M., Jordan, M. E., Cole, J. M., J . PoLymer Sci. 31, 127 (1958). ( 2 ) Miller, A . A , , Zbzd., 42, 441-54 (1960). RECEIVED for review July 9, 1964 ACCEPTED October 9, 1964
R = tert-butyl
Of the several peroxides, only txro exhibited a decrease in efficiency \\ ith increasing cure temperature : dicumyl peroxide ( I I I) and 2-(tert-butvlperoxy)-2-methyl1-chloropropane (IV).
Division of Industrial and Engineering Chemistry, 148th Meeting, ..\CS, Chicago, Ill., September 1964.
THE INFLUENCE OF PEROXIDE CURING SYSTEMS AND CARBON BLACKS IN ETHYLENE-PROPYLENE RUBBER L
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Enjay Laboratories, P . 0. Box 45.Linden, iV, J .
This study has provided some insight relative to the effects of peroxide substituent groups and coagents on the efficiency of peroxides as curatives for ethylene-propylene rubber (EPR) containing various types of carbon black. The tertiary butyl group-such as in di-fert-butyl peroxide-followed b y the cumyl group-such as in dicumyl peroxide-imparts the highest cross-linking efficiency as measured b y modulus. n-Butyl 4,4-bis(tert-butyl peroxy) valerate and dicumyl peroxide are the most promising curatives for EPR owing to the attractive cure cycle and low odor of the former and effectiveness and low cost of the latter. Coagents greatly improve the efficiency of peroxides. The degree of improvement depends on the type of coagent and peroxide as well as the type and oxygen content of carbon black. Thermal black i s the only type of black where polyfunctional coagents yield, in addition to high moduli, higher tensile strengths than those obtained with sulfur.
(EPR) is usually vulcanized system. Dicumyl peroxide and sulfur are. respectively. the most widely used peroxide and coagent. and the performance of this system is described extensively in the literature 17. 8, 9 ) . O n the other hand, information on other peroxides and coagents has been rather limited. In this study. the influence of several peroxideTHYI.ENE-PROPYLESE
RUBBER
E with a peroxide-coagent
coagent curing systems \vas investigated in E P R containing various types of carbon black. T h e purpose \vas to provide a n insight relative to the effects of peroxide substituent groups and coagents on the efficiency of peroxides as curatives for
EPR. T h e modulus developed a t the curing time \vhich corresponds to five peroxide half lives a t 320' F.. \vas the main VOL. 3
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