CRYSTALLIZATION OF POLYDIMETHYLSILOXANE - EFFECT OF SILICA FILLER ANDCURING

Previous publications on the low temperature behavior of polydimethyls iloxane (PDMS) described semiquantitatively or in an incomplete way th e different features appearing during the heating cycle of previously cooled PDMS. The main deficiency of these descriptions is in the quant itative measurement of the heat of fusion This value was reported per mole of chain atom, which has been misunderstood by other researchers as being per mole of structural units. The object of the present work is to give a systematic view of the low temperature behavior of PDMS w ith special attention to the melting behavior of the polymer. The effe cts of the previous cooling rate, molecular weight of the polymer, fil ler addition and crosslinking on the characteristics of d.s.c. thermog rams of PDMS are reported and discussed. A simplified view of the diff erent effects is presented, which allows the calculation of the heat o f fusion of the different samples from the corresponding value of a co mpletely crystalline polydimethylsiloxane. (C) 1998 Elsevier Science L td. All rights reserved.