Branching in natural rubber
1998
Tangpakdee, Jitladda | Tanaka, Yasuyuki
The number of branch-points in natural rubber (NR) was analysed for the rubber from deproteinised fresh field (FL) and high-ammonia (HA) latices, using 13C-NMR and osmometric measurement before and after transesterification of the+ rubber. About two branch-points per chain was found for the rubber from FL-latex and two to five by increasing M in proportion to that of HA-latex. The Huggins ‘k’ constants of the fractionated transesterified rubbers were lower than that of the + original rubbers. The Mw and Mn values of each fraction decreased by about 10% - 50% after transesterification. The gel content of rubber from HA-latex was decreased from 55% to 15% after deproteinisation and further decreased to 1% after + transesterification. The most part of gel in NR was presumed to be formed from some functional groups in NR by aggregation reaction with proteins. The branch-points are originated from other functional groups in NR, presumably such as + phospholipids.
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