MICROCOMPOUNDING OF SMALL SAMPLES OF NATURAL RUBBER

ABSTRACT We describe a microcompounding method that can be used to characterize and compare cured small natural rubber samples. First, commercial Hevea and dried guayule ( Parthenium argentatum ) latex samples were microcompounded to validate the method. Latex was then extracted from the ground branches of six greenhouse shrubs of different ages and genotypes of wild type and transgenic guayule and coagulated into rubber samples. Size exclusion chromatography showed that the samples had different molecular weights and oligomer content. Little variation in physical properties was found between rubber extracted from shrubs of different age within a genotype, but a larger variation among genotypes was found. The new method allows testing of cured rubber samples from experimental variants and early screening out of genotypes to assess the impact of variations in cultivation practices or lab-scale processing conditions on rubber quality.