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Action of dicumyl peroxide on polyolefins and their mixtures

J. Bartoň

Slovak Academy of Sciences, Bratislava

 

Abstract: Cross-linking of low-d. polyethylene (I), atactic polypropylene (II), and their mixts. by dicumyl peroxide (III), benzoyl peroxide (IV), azodiisobutyro-nitrile (V), and Et4Pb was studied. The mixts. of I and II with the initiators were heated in ampuls under N 4 hrs. at 145° (with III), 4 hrs. at 100° (IV), 1 hr. at 100° (V), and 2 hrs. at 195° (with Et4Pb), resp. The gel content was detd. by extn. with CCl4. The degree of cross-linking was detd. by swelling in CCl4 at 75° for 6 hrs. (Flory, CA 44, 5682f). The concn. of cross-link in I was proportional to the quantity of decompd. III; the no. of cross-link was equal to the no. of decompd. mols. of III, and was independent of III concn. The degradation:cross-linking ratio was in this case approx. equal to 0. IV caused much less cross-linking of I as compared with III; the min. concn. of IV needed for gel formation was 5 times as great. V and Et4Pb caused neither degradation nor cross-linking of I and II. No gel was formed in II at the III concns. up to 5.1%. It was assumed that the different behavior of I and II resulted from the different structure of their macroradicals: in I the nonpaired electron was mainly placed at a secondary C atom, whereas in II it was at a tertiary C atom. Recombination of hydrocarbon macroradicals occurred more easily if the nonpaired electron was at primary or secondary atoms, whereas degradation of macromol. chains took place mainly at tertiary C atoms. I-II mixts. were cross-linked by III; the gel concn. depended on II and III content. The higher the II concn. in a mixt. with I, the lower was the gel content and the higher the content of degraded polyolefins.

Full paper in Portable Document Format: 203a169.pdf (in Slovak)

 

Chemical Papers 20 (3) 169–179 (1966)

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