New approach on structure-property relationships of stabilized natural rubbers

The stabilization of natural rubber (NR) was studied using four NR samples, namely, whole natural rubber (WNR), deproteinized natural rubber (DPNR), acetone extracted natural rubber (ANR) and purified natural rubber (PNR). Proteins and lipids, which are non-rubber components in NR, significantly affect storage hardening via gel formation. The main function of the applied viscosity stabilizer was to perturb the dynamics of the NR structure, or alternatively, the formation of gel networks of the rubber chains with lipids and proteins, respectively. The Mooney viscosity and molecular weight of NR samples with the viscosity stabilizer added were found to be almost constant after 12 weeks. Moreover, the NR samples with the viscosity stabilizer required a longer curing time, presumably due to less gel network formation and the conventional packing of linear rubber chains. The results from crosslinking density and molecular weight measurements revealed that the viscosity stabilizer also had a role in stabilizing crosslinks between the chains and preventing the reversion to NR. The new approach of on structure-property relationships of stabilized natural rubbers has been proposed.