INFLUENCE OF NON-RUBBER CONSTITUENTS ON ELASTIC PROPERTIES OF NATURAL-RUBBER VULCANIZATES

Natural rubber (NR), which is derived from latex of the Hevea brasilie nsis tree, contains about 3-5% of non-rubber constituents. These have been found to cause, to some extent, variability of the vulcanizates' properties. Deproteinized NR (DPNR) and technically specified NR (tota l solid rubber; TSR) were initially produced to minimize this variabil ity. This investigation was carried out to determine the constituents of the NR latex which cause variability in the properties of the rubbe r vulcanizates. The contituents of the non-rubber were isolated from t he NR latex and were incorporated separately into purified NR to deter mine their effects on the physical properties of the vulcanizates. The effects of some of these non-rubber constituents on the elastic and s welling characteristics of vulcanizates are reported. In particular, t he change in modulus with humidity for the purified rubber doped with non-rubber constituents is discussed.