(ii) they could be some fraction
of high molecular weight NR that were not dissolved in toluene (swollen gel fraction) and eliminated
in the purification of the raw NR.
In this sense, it has been described that the non-rubber components (mainly proteins and phospho- lipids) of NR can interact at the molecular chain ends of the polymer, forming a tree-dimensional pseudo end-linked network, contributing to the outstanding physical properties and characteristics of the un-vulcanized NR