Abstract
Compatibility is a serious problem in silica-added natural rubber (NR) because of the difference in the polarities of silica and NR. Thus, a coupling agent, such as silane, or a compatibilizer must be incorporated. In this work, amine-functionalized NR was synthesized by an in situ epoxidation process using performic acid and later modified with hexamethylene diamine (HMDA) by a ring-opening reaction. The effects of amine-modified epoxidized NR (ENR-HMDA) content on the cure characteristics, physical and mechanical properties of various NR blends (NR/ENR-HMDA) without filler were studied. ENR-HMDA enhanced the vulcanization process. The maximum torque of compounds increased with the corporation of ENR-HMDA and scorch time and cure time decreased. The cure rate index of NR/ENR-HMDA increased by 98%. All vulcanized rubber blends showed the strain-induced crystallization at high extension. Mechanical properties and crosslink density of the blends were higher than those of NR and NR incorporated with unmodified ENR. Tensile strength was 61% and 43% higher than that for NR and NR/ENR, respectively. The NR/ENR-HMDA blends showed a single Tg that indicated the miscibility of both components. The developed ENR-HMDA compound can be used to improve the compatibility of NR and fillers which would enable the fabrication of a wide range of rubber products.
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Acknowledgements
The authors are grateful for the financial support provided by Prince of Songkla University, Contract No. SCI610441S and to the Department of Materials Science and Technology for all facilities. We also acknowledge Mr. Thomas Coyne for his kind assistance in editing the English and colleagues for their support and encouragement.
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Longseng, R., Khaokong, C. Hexamethylene diamine-modified epoxidized natural rubber and its effect on cure characteristics and properties of natural rubber blends. Iran Polym J 29, 1113–1121 (2020). https://doi.org/10.1007/s13726-020-00865-x
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DOI: https://doi.org/10.1007/s13726-020-00865-x