Abstract
This report relates to the effects of the density and the type of crosslinking of NBR on the rate fo solvent crack growth. The rate of solvent crack growth increases with an increase of crosslinking, while critical extensions decrease. As to the type of crosslinking, the rate of crack growth of C-C bond is higher than that of any other type such as C-S-C or C-Sx-C, whereas the critical extension ratio shows the reverse tendencies.
Critical extension ratios are plotted against Mc1/2, where Mc is the number average molecular weight between crosslinks, showing a linear relation. The slopes of these straight lines do not depend upon the type of crosslinkings, but when these straight lines are extrapolated to zero critical extension, Mc of C-C bond becomes higher than those of others. Discussion was made on these results with respect to the homogeneity and heterogeneity of the crosslinking.
