Use of surface modified silica in reinforcing carboxylated nitrile rubber latex

Coupling agents are a special category of chemicals used to impart interactions between filler and polymer in polymer industry. Applicability of natural polymers (NPs) as coupling agents for silica filled Carboxylated Actrilonitrile Butadiene rubber (XNBR) latex is evaluated. Cellulose, Gelatin Chitin and Chitosan were used as coupling agents for this investigation. Modification of surface of silica particles with NPs was affected by an in-situ surface modification process. Interactions between polar groups of silica and functional groups of NP which hinder the aggregation of silica particles were confirmed by FTIR spectroscopy. The colloidal stability of the unmodified / modified filler (UMF/MF) dispersions was evaluated by observing the phase separation upon standing. Stability of MF dispersions were found to be better than that of UMF dispersions. The reinforcing ability of silica through the surface modification by NPs was assessed by the evaluation of mechanical properties of XNBR vulcanized latex films filled with modified/unmodified fillers. The filler distribution within the rubber matrix was investigated through a metallurgical microscope by observing the films cross sections. NPs like chitin and gelatin were found to be effective coupling agents for silica probably by discouraging filler/filler interactions while encouraging rubber/filler interactions.