Improving thermal and ozone stability of skim natural rubber by diimide reduction

The physical, chemical and thermal properties of diene-based polymers are improved by a chemical modification method such as hydrogenation. Skim natural rubber (SNR) which is mainly comprised of cis-1,4-polyisoprene was hydrogenated by diimide reduction in latex form, using hydrazine and hydrogen peroxide with copper sulfate as catalyst. The effect of various parameters on the level of hydrogenation calculated from proton nuclear magnetic resonance spectroscopy (H-1 NMR) was investigated. The kinetic results indicated that the diimide hydrogenation of skim natural rubber latex (SNRL) exhibited a first order behavior with respect to the C=C concentration. The apparent activation energy of the catalytic and non-catalytic hydrogenation of SNRL was calculated as 9.5 and 21.1 kj/mol, respectively. From the TEM micrograph of hydrogenated SNRL particles, non-hydrogenated rubber core and hydrogenated rubber layer were observed according to a layer model. The results from thermal analysis confirmed that thermal stability of hydrogenated SNR was improved compared with the starting SNR. In addition, the thermal aging and ozone resistance of vulcanized hydrogenated SNR blends were also investigated. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.