FTIR Analysis of Silica-Filled Natural Rubber

Abstract

Abstract The interactions of silica filler in zinc activated, sulfur vulcanized cis-1,4-polyisoprene (IR) were characterized using Fourier Transform Infrared (FTIR)-Attenuated Total Reflectance (ATR) spectroscopy. The variables examined were increased levels of silica and quality of mixing of the batch. The increased silica level resulted in band broadening and a frequency shift to lower wavenumbers of the silica absorbance region (1250-1000 cm−1) due to a combination of physical and chemical adsorption of the rubber and parts of cure system on the silica surface. The peaks that appeared near 1040 and 1017 cm−1 were attributed to physical interactions between silica and the natural rubber. However some chemical bonding of the IR was present as a result of a free radical reaction that takes place during the milling process. Inefficient mixing had an affect comparable to adding less filler, according to the results above. That is, there was less “effective” filler in the poorly mixed samples because poor dispersion promotes agglomeration of the polar silica in the nonpolar hydrocarbon rubber.