ISSN:
0887-6266
Keywords:
degradation, thermal, of copolycarbonates and their blends
;
glassy polymers, thermal chain fragmentation in liquid and solid states
;
copolycarbonates, pure and in blends, chain fragmentation in
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Thermally Activated fragmentation of copolycarbonates PC(TxA1-x) of bisphenol A (unit CA) and the Heat-sensitive diol 1,1,2,2-tetraethyl-1,2-di-(p-hydroxy) phenylethane (unit CT) was studied in the bulk, i.e., in the pure copolymers and in their blends with the polycarbonates of bisphenol A (PCA) or tetramethyl bisphenol A (TMPC). Fragmentation proceeds via dissociation followed by disproportionation at the central C—C bond of the unit CT. The reaction has rates that are convenient to study near the glass transition temperature. The “chemical” time constants τ for the entire reaction and τ2 for the disproportionation step compete with the “physical” time constants δα for segmental motion and δq for fragment diffusion. A cage effect is observed below τ2 = δα and effects of delayed matrix response below τ = δα and τ = δq. Owing to the two latter effects, parameters such as the glass transition temperature and the structure factor of concentration fluctuations do not respond primarily to the fragmentation, but rather to subsequent relaxation and diffusion processes in the polymer matrix.
Additional Material:
14 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/polb.1992.090300209
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