Thermal degradation of deproteinized natural rubber

Thermal degradation of deproteinized natural rubber (DPNR) was investigated by heating at 70 °C and 150 °C for 24 h, which was compared with thermal oxidative degradation of natural rubber (NR). The DPNR was prepared by incubation of the NR latex with urea and sodium dodecyl sulfate at room temperature for an hour followed by centrifugation. FT-IR, 1H NMR and 13C NMR measurements revealed significant differences between DPNR and NR after degradation at 150 °C; that is, cis-1,4-isoprene units of the DPNR isomerized to trans-1,4-isoprene units and vinyl groups, whereas those of NR reacted with oxygen radical and hydroxyl radical generated functional groups. The difference was attributed to an existence of proteins present in the nanomatrix structure, which adsorbed oxygen and water.