Preparation of compounded rubber from natural rubber modified with cardanol and formaldehyde

Abstract

This research studied the preparation of compounded rubber from natural rubber (NR) modified with cardanol-formaldehyde (CF) resin. The cardanol was obtained from cashew nut shell liquid. This resin was synthesized using a condensation polymerization of cardanol with formaldehyde in the presence of a base catalyst. The resin was characterized by infrared and nuclear magnetic resonance spectroscopies. For the preparation of compounded rubber, the aqueous dispersion of the additives was prepared using ball mill for 3 hours. Then the concentrated latex and cardanol-formaldehyde resin emulsion were added and mixed at apropriate time. The latex compounds were coagulated by 5%v/v formic acid and then vulcanized at 150 ํC for 10 minutes. The compatibility of additives and rubber latex in rubber compounds was determined by scanning electron microscopy (SEM) and optical microscope (OM). The mechanical properties, such as tensile strength, modulus, elongationat break, and hardness were also determined. Furthermore, the rubber compounds were studied for thermal properties by aging and thermogravimetric analysis (TGA). The effects of the sulfur quantity (0.5-2 hour) on those properties of rubber compounds were studied. The result indicated that the formulation of compounded rubber, which gave the best properties, were 2 phr sulfur, 2 phr cardanol-formaldehyde resin, and hte approperiate mixing time was 0.5 hour. This formulat ion gave tensile strength of 17.26 MPa, elongation at break of 2183 percent, hardness value of 34.5, and the thermal properties were also improved by incorporation of cardanol-formaldehyde resin.