PENGARUH PENAMBAHAN EKSTRAK BELIMBING WULUH SEBAGAI BAHAN PENGGUMPAL TERHADAP KUALITAS KARET SIR 20

The level of cleanliness and type of coagulant used were overlooked in processing latex into bokar. By reason of expensive and difficult getting formic acid, farmers generally use chemicals such as alum and TSP fertilizer as a coagulant. Thus, in this study is used Averrhoa bilimbi as an alternative coagulant and see its effect on the quality of rubber SIR 20. Latex coagulated with Averrhoa bilimbi extract water (100%, 75%, 50%, and 25%) and 2% formic acid as comparison, to achieve 4.5 to 4.8 of pH in the plastic tub and time of coagulation recorded. Coagulum (which had coagulated latex) observed in color, odor, and texture changes for 2 weeks. Then, coagulum milled with using a creeper to further tested dry rubber content, ash content, the initial plasticity (Po), plasticity retention index (PRI), levels of substance evaporates, and the levels of impurities. The results showed that the rubber is used higher concentration Averrhoa bilimbi extract produce higher Po and Po optimum achieve in Averrhoa bilimbi 75% extract. The optimum PRI is resulted by the higher Averrhoa bilimbi extract. The higher content of Averrhoa bilimbi extract, the greater of ash content, but the ash content is still under standard rubber SIR 20. The lower impurities levels rubber with Averrhoa bilimbi higher extract and when it compared with formic acid. For volatile substances, Averrhoa bilimbi extract showed almost the same results with formic acid coagulant. From these obtained data, the use of Averrhoa bilimbi extracts as an alternative coagulant should be considered