Urea as a single denaturing agent in deproteinisation of natural rubber latex

Abstract

This paper describes the utilisation of urea as a single chemical agent to obtain deproteinised high ammoniated natural rubber latex (HA-NRL). The role of urea in HA-NRL deproteinisation was further investigated by employing two different concentrations of urea solution which are low (0.01–0.05%) and high (1.0–5.0%) concentrations. The study assessed the potential usage of urea as a single denaturing agent in the presence of neither stabilising agent nor additives during the deproteinisation process. The effect of different urea concentrations on properties of deproteinised NRL was further scrutinised by using sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE), nitrogen content analysis, extractable protein (EP) content, Zeta potential, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and physical strength. The presence of residual urea is pertinent as the concentration of urea increases while contributing to the increase of total nitrogen content in the resultant film. Leaching the film with hot water is sufficient to remove the residual urea as supported by an ATR-FTIR analysis. Initial exploratory data analysis of low and high urea concentrations on the effect of nitrogen content, EP, surface charge properties of latex and green strength of the deproteinised NRL were evaluated and their relation to each factor was further discussed. Based on the initial findings, urea was observed to be less effective as a single denaturant. Nonetheless, the properties of the deproteinised HA-NRL treated with urea were revealed to be markedly influenced by the urea concentration.