摘要: The tear strength of polydimethylsiloxane (PDMS) networks was found to be only about one-third as large as that of polybutadiene (PB) or polyisoprene (PI) networks of similar M sub c when the tear strength was measured under thres... 展开 The tear strength of polydimethylsiloxane (PDMS) networks was found to be only about one-third as large as that of polybutadiene (PB) or polyisoprene (PI) networks of similar M sub c when the tear strength was measured under threshold conditions, i.e., at high temperatures, low rates of tearing, and with swollen samples. This striking difference in strength is attributed to the smaller length and extensibility of PDMS molecules in comparison with PB or PI molecules of the same molecular weight. Networks formed by trifunctional or tetrafunctional endlinking reactions with difunctional PDMS polymers were found to be only slightly stronger under threshold conditions, by up to 30 per cent, than PDMS networks formed by random crosslinking to the same M sub c. Endlinked PB networks were found to have substantially the same threshold strength as randomly-linked PB networks of the same M sub c. Thus, the threshold tear strength does not appear to depend strongly upon the uniformity of network strand lengths. (Author) 收起