ISSN:
0021-8995
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The radiation chemical process in polyvinyl chloride has been studied by means of electron spin resonance, optical spectroscopy, and measurement of gas evolution. The chief technique was to irradiate samples at -196°C. and then follow the change or changes with rising temperature. Resonance results showed that, on irradiation, several primary radicals, such as —CH2—ĊH—CH2—, —CHCl—ĊH—CHCl—, etc., were produced. Among them some —CH2—ĊH—CH2— radicals could recombine to form crosslinks during irradiation even at -196°C. A mechanism for the discoloration of PVC, based upon results obtained by these three different methods, has been postulated. Discoloration is caused by the formation of polyenyl radicals or polyene molecules of considerable conjugation lengths, some as long as 9 conjugated double bonds. Polyenyl radicals are produced as a result of a thermally induced secondary reaction of the —CHCl—ĊH—CHCl— radical, above -70°C., thereby accompanied by hydrogen chloride detachment following the so-called “zipper” mechanism. An equation relating the pressure of evolved HCl to the reaction temperature has been derived by a simple kinetic treatment of the zipper reaction. Some effect of heat treatment and increasing dose on discoloration was discussed.
Additional Material:
16 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1962.070062405
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