Copolymerization of ethylene with vinyl acetate. I. Effect of polymerization temperature on degree of branching
| Autor: | I. A. Zlochower, A. E. Kober, M. J. Wisotsky |
|---|---|
| Rok vydání: | 1971 |
| Předmět: |
chemistry.chemical_classification
Materials science Ethylene Polymers and Plastics General Chemistry Branching (polymer chemistry) Surfaces Coatings and Films Crystallinity chemistry.chemical_compound chemistry Polymerization Polymer chemistry Materials Chemistry Copolymer Vinyl acetate Moiety Alkyl |
| Zdroj: | Journal of Applied Polymer Science. 15:1737-1742 |
| ISSN: | 1097-4628 0021-8995 |
| DOI: | 10.1002/app.1971.070150717 |
| Popis: | The degree of branching of a series of ethylene–vinyl acetate copolymers was found to be strongly dependent upon polymerization temperature. The copolymers were prepared by free-radical polymerization and had low molecular weights and molar ratios of ethylene: vinyl acetate greater than 3:1. Nuclear magnetic resonance and infrared studies showed that copolymers prepared at 150°C were highly branched and had little crystallinity. Branches were mainly alkyl groups on the polymethylene backbone segments. There was no evidence of δ-acetoxyalkyl branches. Long branches originating by intermolecular H abstraction from the acetylmethyl groups were also expected but could not be detected. These results were consistent with an intramolecular “backbiting” mechanism similar to that found in ethylene homopolymerizations. There was little or no participation by the vinyl acetate moiety in the branching scheme. Copolymers prepared at about 90°C had very few long or short branches and were more crystalline. Copolymers prepared between these temperatures had intermediate degrees of branching and crystallinity. |
| Databáze: | OpenAIRE |
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