Improving the Adhesion between Pineapple Leaf Fiber and Natural Rubber by Using Urea Formaldehyde Resin

Abstract

Green composites, especially that are reinforced with natural fibers, have received a great deal of attention due to the problems of global warming and resources depletion. Pineapple leaf fiber (PALF) is an interesting choice because of its high mechanical properties and it is obtained from agricultural waste. In this work PALF is combined with natural rubber (NR) to produce green rubber composite with enhanced mechanical properties. Since the two materials are so different in their stiffness and polarity, poor interfacial adhesion and thus low stress transfer, between NR and PALF may be expected. Attempts were made to use urea formaldehyde (UF) resin to improve the adhesion between PALF and NR. PALF was coated with different amounts of UF resin in solution. The fiber was characterized with FTIR, XPS and SEM. Uniaxially aligned PALF reinforced rubber composites with a fixed amount of 10 parts per hundred of rubber (phr) PALF were prepared. The adhesion between PALF and NR was evaluated from the tensile stress-strain curve and fracture surface of the composite. It was found that UF resin had negligible effect in improving the stress transfer but rather reduced it as shown in the stress-strain curve. Thicker coating of UF resin led to lower reinforcement effect and, hence, lower modulus. Stress at break, on the other hand, increased with increasing the coating thickness.