Effect of potassium oleate (PO) on the colloid stability of high ammonia (HA) natural rubber latex (NRL) after the freezing and thawing processes

摘要

High ammonia (HA) natural rubber latex (NRL) is generally very sensitive at lower temperature and will form big rubber lumps after the freezing and thawing processes. The growth of ice crystals in an aqueous medium during freezing causes the rubber particles to move closer together and thus disrupts the protein cloud surrounding the latex particles. The broken protein cloud causes rubber particles to coalesce and form big lumps after the thawing process. However, this phenomenon did not occur when potassium oleate (PO) was incorporated into the HA NRL medium. PO acted as a colloid stabiliser by means of adsorbance at the rubber latex surface, thus preventing the coalescence of rubber particles from occurring. This study investigated the effect of PO loading (0, 0.1, 0.2, 0.3, 0.4, and 0.5 phr) on the colloid stability of HA NRL after being subjected to both freezing and thawing. These latex mixtures were frozen by cooling it at -4 degrees C for 24 h and thawed by allowing them to stand at room temperature for 1 h followed by heating at 40 degrees C for another hour. The results obtained showed that the PO improved the colloid stability of HA NRL in terms of morphological properties, viscosity, and mechanical stability time values. Particle-size distribution of latex mixtures, however, did not vary even after freezing.