English Abstract
Development of Thermoreversible Crosslinking Rubber using Supramolecular Hydrogen Bonding Networks
Keisuke CHINO
Research & Development Center, The Yokohama Rubber, Co. Ltd., Kanagawa, Japan
Nippon Gomu Kyokaishi,(2005),78(3),106-110 General Review in Japanese

Thermoreversible Hydrogen-bond crosslinking isoprene rubber (THC-IR) was synthesized by modification of isoprene rubber (IR) with maleic anhydride followed by the addition of 3-amino-1,2,4-triazole(ATA), in solid phase. The mechanical properties of the resulting rubber were more similar to the sulfur-vulcanized rubber than general thermoplastic elastomers (ex. SEBS). Although the tensile strength and elongation at break were lower than those of a corresponding sulfur-cured rubber, the moduli were as high as those of sulfur-cured rubber.
Reforming could be repeated more than 10 times without significantly changing its mechanical properties. Differential scanning calorimetry (DSC) revealed that the superior mechanical properties and good recyclability are attributable to the strong hydrogen bonding.
The TRC-IR showed an endothermic transition peak at around 185 on the DSC chart, indicating cleavage of the hydrogen bonding. Moreover, small angle X-ray scattering (SAXS) clarified the crosslinking point is aggregated structure of ca. 5 nm by supramolecular hydrogen bonding.
A hypothetical model was suggested which comprises strong crosslinking moiety formed by the seven points hydrogen bonds. The thermoreversible crosslinking system could be applied to EPM and AEM, as well.
These rubbers also showed superior mechanical properties as well as excellent recyclability.

Rubber, Maleic anhydride, Amino triazole, Thermoreversible Crosslinking, Supramolecular Hydrogen Bond, Recycling