HEAT-SENSITISATION OF AnnONIA-PRESERVED CENTRIFUBED NATURAL RUBBER LATEX CONCENTRATE BY POLYVINYLMETHYL ETHER. I. EFFECTS DF MATURATION, FORMER TEMPERATURE, OWELL TIME, LATEX pH, LEVEL DF ZINC OXIDE, DILUTION. AND CONCENTRATION AND MOLECULAR WEIGHT OF POLYVINYLMETHYL ETHER

ABSTRACT

This and a subsequent paper report the results of a systematic investigation of the factors which affect the heat-sensitisation of natural rubber (NR) latex by polyvinylmethyl ether (PUME). Possible mechanisms for the heat-sensitisation of aqueous latices by uateisoluble polymers such as PUME are outlined, and observations concerning the behaviour PUME in aqueous solution and the effects of maturation, former temperature, dwell time, latex pH, level of zinc oxide, dilution, and level and molecular weight of PUME upon heat-sensitisation are reported and discussed. The cloud-point temperature of PUME in aqueous solution is insensitive to polymer concentration, ionic strength, pH, polymer molecular weight, concentration of fatty-alcohol ethoxylate, and concentration of a hydrogen-bond breaker such as urea. Results for the effects of the variables listed above upon the heat- sensitisation being a consequence of PVME adsorbed at the surface of the rubber particles. rather than of PVME dissolved in the aqueous phase of the latex.