Realising the Potential of Pineapple Leaf Fiber as Green and High-performance Reinforcement for Natural Rubber Composite with Liquid Functionalized Rubber

Abstract

In this work, it is attempted to demonstrate the potential of natural fiber namely pineapple leaf fiber (PALF) as high performance green reinforcement for natural rubber. Liquid carboxylated isoprene rubber was used as an adhesion promoter (AP) to improve the adhesion between the fiber and the rubber matrix. Three types of fibers, i.e. untreated, sodium hydroxided treated and silane treated, were used. PALF and carbon black were combined to form hybrid reinforcement. Fiber content and carbon black were kept at 10 and 30 parts (by weight) per hundred of rubber (phr), respectively. Preferentially aligned fiber composite rubbers were prepared and tested using dynamic mechanical analysis. Scanning electron microscopy was used to study the cryogenic and tensile fracture surfaces of the composites. It was found that storage moduli of the composites containing the liquid AP dramatically increase in the temperature range above the glass transition temperature of the matrix. Fiber treatment provides negligible effect on storage moduli without the liquid AP. On the contrary, significant additional effects of sodium hydroxide treatment and silane treatment on the storage moduli were obtained when the liquid AP is present. This indicates an interacting and hence synergistic effect of the surface treatment and the liquid AP. Scanning electron microscopy images revealed that large PALF bundles break down into microfibers, in the presence of the liquid AP, to provide more efficient reinforcement. The highest room temperature modulus obtained was 230 MPa. Mechanism for the improvement in the reinforcing efficiency will be proposed and discussed.