An Investigation of Coconut Shell Extract as an Alternative Coagulating Agent for Natural Rubber Latex

Abstract

The rubber industry in Sri Lanka is one of the most important industries, earning a significant amount of foreign earnings. Raw natural rubber processed from coagulation of natural rubber latex is the main raw material used in the local rubber industry. Formic acid is the widely used chemical to coagulate natural rubber latex. In the face of export restrictions and rising cost of this imported material, the use of formic acid in rubber processing has now become unaffordable. The use of coconut shell extract as an alternative coagulating agent for natural rubber latex was investigated in this study. Coconut shells are considered as wastes of coconut based products that have not been utilized efficiently. By using these abundant bioresources as raw materials, we were able to produce coconut shell extract at a comparatively low cost. To understand the effect of coconut shell extract as an alternative coagulant material for natural rubber latex, different ratios of coconut extracts prepared using hot water extract technique was used to coagulate the latex. Ribbed Smoked Sheet (RSS) rubber was manufactured using the coconut shell extract according to the standard manufacturing procedures. Raw rubber properties of RSS rubber were evaluated. The results revealed that the addition of coconut shell extract as an alternative to the formic acid substituent gives similar effect on the raw rubber properties of the RSS except Plasticity Retention Index (PRI). Change of sheet color of RSS could be observed with the addition of coconut shell extract as the coagulant. Overall results of the study found the potential of the application of coconut shell extract as an alternative coagulanting agent for formic acid for coagulation of natural rubber latex.