Synthesis of sonochemical chloroacetated natural rubber and its potential use in passenger car tire tread

Abstract

This article describes the preparation of chloroacetated natural rubber (CNR) through the epoxidation of natural rubber (NR) latex with performic acid, followed by the reaction with chloroacetic acid. Ultrasound waves were utilized to accelerate the epoxidation reaction. The CNR samples obtained at various epoxidation durations were analyzed by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography, and differential scanning calorimetry techniques. Results showed that the chloroacetate content in CNR increased with increasing epoxidation time, i.e., the chloroacetate contents were 17.4, 18.5, and 19.7% at epoxidation times of 30, 45, and 60 min, respectively. The prepared CNR samples were then employed to replace NR in silica-filled tire tread compounds based on a 70/30 solution styrene butadiene rubber (SSBR)/NR blend. It was found that, compared with NR, CNR provided significantly higher rubber-silica interaction, leading to improved mechanical and dynamic properties. Such replacement not only reduced heat build-up and rolling resistance, but also increased the wet grip index, which is highly beneficial for the production of high-performance passenger car tires. It could be observed that the improvements in rubber properties and tread performance were more obvious when the chloroacetate content of CNR was increased, probably due to the enhanced rubber-filler interaction, as demonstrated by the increased bound rubber content.