Utilization of Natural Rubber Latex as Raw Materials for Rubber Shoe Outsole

The utilization of natural rubber (NR) latex waste as raw materials is a common practice to improve the sustainability of the environment and to reduce the cost. The objective of this task is to utilize NR latex waste as new material for rubber shoe outsoles. The NR latex waste used in this project was based on old NR latex (OL), compounded NR latex (CL) and rejected NR glove (RG). The OL and CL were subjected to coagulation process with 2% of sulphuric acid. While the vulcanized waste (CL after coagulation and RG) underwent the reclamation process under shearing mechanism. The preliminary study on the loading of calcium carbonate (CaCO3) at 60 and 70 phi was carried out, in which 60 phr loading achieved the properties required for the shoe outsole. Subsequently, the rubber compounds with different types of raw materials (SMR20 and reclaim rubber) and combination of 50/50SMR 20/reclaim rubber with 60 phr of CaCO3 loading were prepared. Based on the mechanical and physical properties, 100% OL showed high tensile strength with low value of abrasion resistance and compression set. While for combination of SMR20 with reclaim rubber (RG and CL) showed high tensile strength and high abrasion resistance but inversely for compression set. Based on the specification of rubber shoe sole, the 100% OL and 50/50 SMR20/OL are suitable NR latex wastes that can be used as raw material for rubber compound for shoe sole application.