Interfacial and physico-mechanical properties of walnut shell fiber reinforced polyester matrix composites

Abstract

Turkey produces over 200,000 tons of walnut annually as the fourth largest producer in the world. Walnut shells amount to 40-60% of the total weight, rendering over 100,000 tons of shells per year, mostly as waste. A limited quantity is utilized for fiberboard manufacturing, some as solid fuel or as scrubbing material in the chemical and metal industries. The purpose of this study is to develop low-cost polyester composites with enhanced physico-mechanical properties by using walnut cellulosic fibers as a reinforcement phase for polyester resin. The process not only makes production more economical but also reduces waste. The shells were ground and a detailed characterization of the waste fibers was carried out by scanning electron microscopy, X-ray diffraction, FTIR, laser diffraction and He gas picnometer techniques. The effects of the filler to matrix ratio as well as chemical treatment of walnut fibers on the physical and mechanical properties of the composite were determined. The composites were characterized by means of measurements for porosity, density, three point bending strength, impact resistance and hardness. The structure-property relationship of developed composites was discussed. Optimum physico-mechanical properties were obtained through a hydrophobic solution treatment of the powder since this provided better processability and enhanced interfacial adhesion.