Investigation of Physical and Mechanical Properties of Polyester Matrix Polymer Composites Containing Walnut Shell Waste and CEN Sand

The aim of this study is to investigate the potential of using walnut shells, which are agricultural waste, in polymer composites in order to reduce the environmental impacts and contribute to the production of sustainable materials. In this direction, Flame Retardant Polyester (FRP) was used as a binder in the production of composite materials, while standard CEN sand and Waste Walnut Shells (WWS) were used as filler materials. While creating composite mixture groups, FRP was preferred at 50% and filler at 50%. Then, while keeping the FRP ratio constant, WWS was replaced by standard CEN sand at 25%, 50%, 75% and 100% by volume. The apparent density, water absorption, porosity, ultrasonic pulse velocity (UPV) and compressive strengths of the produced polymer composites were investigated. In the specimens where WWS was replaced by 100% with standard CEN sand, a decrease of 27%, 20% and 28% was detected in compressive strengths, UPV and apparent density values, respectively, compared to the control specimen. The most negative behavior in terms of water absorption was observed in the specimen coded WS75 with a water absorption rate of 0.80%. The use of WWS in polymer composite production is evaluated as an economical raw material source, contributes to the prevention of environmental pollution and is also important with its potential to be recycled into the economy.