An analysis of the Plasticity Retention Index of the Standard Malaysian Rubber Scheme
1989
Sambhi, M. S.
Molecular degradation is the main process occurring during the Plasticity Retention Index {PRI) test of commercial grades of raw natural rubber. The relationship between Wallace plasticities and number-average degrees of polymerisation allows one to express the PRI in terms of number-average degrees of polymerisation. The degradation data, for a number of commercial grades of natural rubber, can be represented by typical first-order type of kinetic equations. For such rubbers, the dependence of PRI on the initial Wallace plasticity and the chain scission rate constant is determined. A generalised treatment of the factors that influence the PRI value is presented and some of the empirical observations made with regard to the PRI are rationalised. The effectiveness of the PRI, as a measure of the susceptibility of raw natural rubber, is gauged.
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