A novel thiourea based interfacial modifier for silica‐filled natural rubber composites

Abstract In this paper, a novel interfacial modifier, namely 2‐hexylthiouronium bromide (HTB), for silica has been synthesized and applied into silica‐filled natural rubber (NR) composites. HTB was synthesized from the reaction of thiourea with hexyl bromide at 65°C. Fourier‐transform infrared (FTIR) and Proton nuclear magnetic resonance spectrometry ( 1 HNMR) were used to characterize the chemical structure of HTB. Different loadings of HTB were used to prepare a series of silica‐filled NR composites with the aim of verifying the optimal loading of HTB. The cure characteristics, swelling, mechanical, aging and morphological properties of the resulting composites were studied and compared with the unmodified silica‐filled NR composite. The thermal stability of the composites were also studied by thermogravimetric analysis. By examining the properties of the composites, it was found that the addition of HTB had a significant effect on the properties of the silica‐filled NR composites, resulting in shorter scorch and cure times, as well as better swelling, mechanical, aging, and thermal properties than those of the unmodified composite. Furthermore, it was found that 2.5 phr loading of HTB was preferable to obtain a composite with superior tensile properties as its composite's tensile strength increased by 104% over the unmodified composite.