Behavior of cis-Polybutadiene during Mastication
| Autor: | K. W. Rollmann, Gerard Kraus |
|---|---|
| Rok vydání: | 1965 |
| Předmět: |
chemistry.chemical_classification
Polymers and Plastics Radical chemistry.chemical_element General Chemistry Polymer Photochemistry Oxygen Surfaces Coatings and Films Catalysis Polybutadiene chemistry Natural rubber visual_art Materials Chemistry visual_art.visual_art_medium Molar mass distribution Bond cleavage |
| Zdroj: | Rubber Chemistry and Technology. 38:493-508 |
| ISSN: | 1943-4804 0035-9475 |
| Popis: | Cold mastication of natural rubber in presence of oxygen leads to scission by a shear mechanism with subsequent stabilization of the free radicals by oxygen, while at high temperatures oxidative scission becomes the dominant mechanism. Studies of the behavior of cis-polybutadiene reveal that similar reactions are effective, but occur at much reduced rates. Shear degradation is particularly difficult to achieve in typical cis-polybutadienes. This is related to the molecular weight distribution of these polymers which usually lack the very high molecular species most subject to shear-induced degradation, in agreement with the theory of F. Bueche. It is shown that when such a high molecular weight fraction is supplied, shear breakdown may be realized. All cis-polybutadienes undergo oxidative breakdown at high temperatures, the scission rate becoming appreciable above 140° C. A number of oxidation catalysts have been found which markedly increase the scission rate without leading to a correspondingly large increase in crosslinking. Significant improvements in processing may be realized in this manner. |
| Databáze: | OpenAIRE |
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