Pyrolysis of polyacrylonitrile and related polymers—VI. Acrylonitrile copolymers containing carboxylic acid and amide structures

✍ Scribed by N. Grassie; R. McGuchan

• Publisher: Elsevier Science
• Year: 1972
• Tongue: English
• Weight: 659 KB
• Volume: 8
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(72)90032-8

✦ Synopsis

Acidic comonomers exert a strong initiating effect on the exothermic nitrile group oligomerization in polyacrylonitrile. In contrast to the sharp intense transitions for pure homopolymers, the exotherms for the copolymers are very broad with much reduced differential temperatures. This is explained by the free radical mechanism in the homopolymer changing to a concerted or ionic mechanism in the copolymers. The detailed mechanism of acid initiation is complex; the possibility of imide intermediates is discussed. From the point of view of carbon fibre productioa, the thermogravimetric behaviour of these copolymers is better than that of the homopolymer since the chain scission and volatilization which occur during intense exotherms are greatly reduced.

Acrylamide also initiates the exotherm but in this case the copolymer exotherm can be more intense than that of the homopolymer so that the free radical nature of the reaction is retained in acrylamide initiation. In contrast, the behaviour of a closely related copolymer system containing amideoxime structures resembles that of the acid rather than the acrylamide copotymers.