Possible role of soap strength on mechanical stability and other properties of low quality LA-TZ natural rubber latex concentrate

Abstract

Ever-growing impact of rubber and its products form an inseparable and integral part in human life. But today, rubber industries suffer from lack of quality latex for production. Over the last few decades, various efforts have been carried out to study the ability of Fatty Acid soaps to enhance stability of latex upon mechanical forces. However, an investigation has never been carried out in Sri Lanka on property variation of low quality latex upon soap addition. This study was undertaken with the view to fulfill this requirement. Current study consists of determination of MST and other properties of low quality latex and brief investigation on anti foaming behaviour of phenol on latex base. Latex was obtained with absence of added soap on a special request from centrifuge plant of Lalan group. They were collected from small holders of Matale, which represents the non-specific climatic conditions for latex production. Soap was added in different strengths at different maturity times. Following properties were investigated ut intervals: MST, KOH number, Viscosity, Foaming Height, and Conductivity. Anti-foaming behaviour of phenol on latex base was determined. Results of this study provide information of low quality latex upon soap addition and aging. Out 01" entire investigated properties response to the soap was remarkable in MST and Foaming Height upon aging. Viscosity showed great variation within 3 weeks maturation. Prevalence of soap was critical between soap levels of 4.2x 10-4and 5.0x 10-4 moles per 100g of latex. Results suggest that the system attain to critical micelle concentration within this range. Minimum soap level that is necessary to create observable change in MST and Foaming Height lies between 0.5x 10-4and 0.84x I0-4 moles per 100g latex. Soap level of 0.5x I0-4makes great variatiohs in Viscosity, Conductivity and KOH No. Effect of soap on Conductivity and KOH No diminishes after 8.41 x Io' moles of soap. Both properties are responsible for the total molecules that are present in the ionized form and not the total molecules in the medium. Since, the soap effect upon KOH No diminishes after certain soap level it cannot be used as an identification of soap addition to latex. However added soap can be identified by variation in the Foaming Height. Significant relationship between soap addition and foaming height reveals that the foreign soap molecules increase the froth formation in latex. Phenol addition can reduce the foaming in latex. But it reduces the MST of the latex and hence detri mental for the quality of latex. Variation in MST and Viscosity by deliberate soap addition primarily causes by Fatty Acid soap ions that are adsorbed at the particle surfaces. Variations in KOH No, Conductivity and Foaming Height has brought about by consequent changes taking place in the medium.