ISSN:
0022-3832
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Divinylbenzene (48%)/ethylvinylbenzene copolymer was converted to a series of pyrolytic derivatives. Enough of the carbon bond network remained intact throughout thermal rearrangement and condensation to retain the original gross shape of the copolymer in the final polymer carbon. Although a carbon residue (6% by weight) was obtained by direct heating of the copolymer, yields were increased eightfold by preoxidation or prechlorination. Such an alteration of thermal degradation is obviously a complex process involving both “inhibition,” in the ordinary sense, and a considerable contribution toward an increased valence network density. As a consequence, the average molecular weight of volatile fragments evolved during carbonization is inversely proportional to the oxygen content of the original hydrocarbon polymer. Pyrolysis of divinylbenzene copolymer, containing 18% oxygen, resulted in a 50% volume shrinkage, 50% weight loss, and a 100% density gain. Unless these data are attributable to extensive microporosity, it is difficult to account for the sorption of up to 3 cc. of helium gas per gram of polymer carbon at 30°C. and 600 mm. pressure; and calculated surface areas as large as 1400 sq.m./g. Abrupt changes in the progress of polymer carbon formation occurred between 600 and 700°C. The residue became rigid; vigorous evolution of volatile products, principally hydrogen, suddenly diminished; and paramagnetic resonance absorption (unpaired electron concentration) dropped about tenfold while d.c. resistivity decreased 106 ohm cm. In this region, also, x-ray patterns were most diffuse, exhibiting no maxima characteristic of carbon scattering in either hydrocarbons or condensed rings. Finally, the x-ray patterns of polymer carbon intermediates became less diffuse in samples prepared at 700°C. or above. Yet, scattering indicated the presence of crosslinked graphitic layers of such stability that reordering or true graphitization did not occur at 2400°C.
Additional Material:
18 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1955.120168202
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