Effect of hydrazine content on mechanical and thermal properties of hydrogenated natural rubber

Abstract

Hydrogenated natural rubbers (HNRs) with two different degrees of hydrogenation were prepared by the latex method. Effect of the molar ratio of hydrazine to double bonds was investigated. Proton nuclear magnetic resonance spectroscopy revealed that the structure of HNR contains some trans isomer formation. Degrees of hydrogenation were about 32% and 41% when the N₂H₄ molar ratios were respectively 1 and 1.5, whereas the trans isomer increased from 0 to 19%, depending on the degree of hydrogenation. Compared to the NR, a faster curing reaction with higher maximum torque was recorded for the HNR due to trans-isomer formation, resulting in a greater crosslink density in the HNR. The presence of a trans isomer together with a high crosslink density degraded the ability of the rubber molecules to relax. The tensile modulus of NR was increased by hydrogenation, but with reduced tensile strength and elongation at break. An increased percentage of hydrogenation improved thermal stability of the NR by at least 16°C at 32% hydrogenation, and escalated thermal degradation of the NR, resulting from a reduction of double bonds in the HNR.