The Impact on Properties of Block Rubber of Using Adulterated Coagulants in Cup Lumps of Natural Rubber

Cup lumps are raw materials used in block rubber production and commonly contain adulterants among the chemicals used for rubber coagulation. This study aimed to identify the composition and concentration of components in commercial coagulants for producing cup lumps in the Northeastern and Northern regions of Thailand. A further goal was to study the impact of using these cup lumps to make block rubber. Detection of coagulant concentration by ion chromatography found that 25% of the samples were composed of formate ions and 50% of the samples were composed of sulfate ions ranging from 17.89 to 93.46% and 36.17 to 97.74% by weight, respectively. Among the adulterated coagulants, they were mixed with formate ions and chloride ions in 18.75% of the samples and sulfate ions mixed with chloride ions in 6.25% of the samples. Additionally, block rubber containing adulterants had Po, PRI, and Mooney viscosity values that meet the lower grade STR 20 standard. Block rubber made from cup lumps coagulated using formic acid showed physical properties that met the STR 5 standard.