Composite Materials for Shoe Soles

Abstract

The worldwide trend towards using inexpensive, nontoxic and durable materials from renewable resources or industrial wastes, which contributes to ecological and sustainable development has already caught mainstream attention. Use of rice straw, wood fibre, vegetal fibres, rice husk, groundnut husk, wheat straw etc. as filling material is on the rise. This study explores the potential use of a few of such industrial and agricultural wastes as a filling material in the conventional shoe sole polymers, with ease of adoption being a priority. Based on the feasibility of research study, thermoplastic rubber was chosen as the polymer matrix, and the synthesis of thermoplastic rubber granules as the stage of experimentation. Leather dust, rice husk and wheat straw/husk were used in bulk and powder forms and in various percentage loadings to synthesize different composites. Testing of various mechanical properties (hardness, tensile strength, abrasion etc.) was carried out for these composites and compared to that with CaCO3 as the filler. Addition of any filler resulted in an increase in specific gravity, hardness and abrasion and decrease in tensile strength and elongation at break. 15% loading is above the saturation limit of the polymer matrix and 10% is a more optimum loading. Powder forms gave better results than the bulk forms. Rice husk and wheat straw/husk give better resulting properties than CaCO3 filled composite, and offer a cost advantage over the original compound with no filler loading. This may contribute to an easier and quicker shift towards sustainability in the near future.