An experimental verification of gel network formation theories

✍ Scribed by Scott, Kenneth W.

• Publisher: John Wiley and Sons
• Year: 1962
• Weight: 928 KB
• Volume: 58
• Category: Article
• ISSN: 0022-3832
• DOI: 10.1002/pol.1962.1205816629

✦ Synopsis

Abstract

Precise sol fraction determinations over the range 0.07–1% have been made on milled natural rubber crosslinked with varying amounts of the quantitative crosslinker, dicumyl peroxide. The benzene‐soluble sol fraction was determined following an initial acetone extraction to remove the nonrubber, soluble reaction products of the crosslinking. The milled natural rubber had a viscosity‐average to number‐average molecular weight ratio close to that of a random or most probable distribution of molecular weights. The sol fraction dependence on the amount of crosslinking has been compared with the predictions of gel network formation theory. The agreement between theory and these experimental results is good, both as to the form of the molecular weight distribution and the number average molecular weight. This agreement establishes the validity of calculation of either the number of crosslinks or the molecular weight distribution from sol fraction measurements when the other is known. The extent of permanent molecular scission that might occur during the crosslinking reaction was also determined from these data. The ratio of permanent molecular scissions to crosslinked units introduced is not significantly different from zero, and at the 95% confidence level this ratio can be said to be less than 0.0048. A number of simple, rapid methods for estimating molecular weight distributions from sol fraction–crosslinking studies are described.