Submitted to: Thermochimica Acta
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/1/2008
Publication Date: 8/15/2008
Citation: Martins, M.A., Moreno, R.M., McMahan, C.M., Brichta, J.L. 2008. Thermooxidative study of raw natural rubber from Brazilian IAC 300 series clones. Thermochimica Acta. 474:62-66. Interpretive Summary: The USDA’s Domestic Natural Rubber project has studied the biochemistry of rubber biosynthesis in different rubber-producing species with a focus on natural rubber from Parthenium argentatum, guayule, a woody desert shrub suitable for cultivation in some parts of the United States. However, interspecific comparisons have been invaluable in the elucidation of the molecular biology, biochemistry, and botany of natural rubber biosynthesis. Our Brazilian collaborators at Embrapa and at APTA/IAC bring expertise in many aspects of rubber production by the Brazilian rubber tree, Hevea brasiliensis, the primary source of natural rubber in the world today. The collaborative study of H. braziliensis will therefore contribute to development of P. argentatum or other domestic rubber-producing species. In the example presented here we have learned that oxidative stability of rubber varies by clone in Hevea, and that during the thermal process, Hevea rubber forms crosslinked and cylic network structures in both inert and oxygen atmospheres. Gel structures in Hevea are well known and may be responsible for some of the outstanding performance of the rubber. In contrast, guayule has poorer oxidative and thermal stability, yet also forms these same crosslinked/cylic structures in response to heat. (data not included in this publication).
Technical Abstract: The improvement of rubber tree species is of key importance due to the worldwide market demand of this renewable material essential for several types of industries. The thermal performance of natural rubber produced from new clones of IAC 300 series, and the Malaysian RRIM 600 clone (used as control) have been evaluated using DSC and TGA/DTG techniques in air and nitrogen atmospheres. The results have shown that in oxidative atmosphere, the thermal stability of the Brazilian clones was slightly better than that of the Malaysian clone RRIM 600, and that, in an inert atmosphere, there are no significant differences in the thermal behavior among them. The natural rubbers from IAC clones have shown good thermal stability up to 300 oC in inert and oxidative atmospheres, which is important for several industrial applications. The decomposition changes from a one step process to a three step process, when moving from an inert to an oxidative atmosphere. The index of thermal stability has shown that the natural rubbers have higher thermal stability in inert atmosphere.