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Abstract
Epoxide groups in Natural Rubber. II.
13C-NMR study of undegraded Natural Rubbers
The level of epoxide groups on the natural
rubber main-chain molecule is examined by 13C-NMR spectroscopy. The results
show that while all the rubber samples contain trans isoprene units, purified
rubbers from fresh latices contain no detectable amount of epoxide groups.
This is also found to be the case for fractionated rubbers of different
molecular weights, rubber samples of different clonal origin as well as
rubbers isolated from different zones of centrifuged fresh latex. Nevertheless,
of the six commercial solid rubber samples examined, SMR L and SMR 10 were
found to contain trace amount of cis epoxide, the levels of which are similar
to that of trans isoprene units. It is concluded that natural rubber has
no detectable amount of epoxide groups on the main-chain molecule.
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