Thesis (M.Sc.)-- Chulalongkorn University, 2008

Mechano-chemical devulcanization process for vulcanized natural rubber (NR) was investigated in this study. A novel devulcanizing agent used in this study was thiosalicylic acid. Thiosalicylic acid/n-butylamine and diphenyl disulfide were used as the references. Optimum condition for devulcanization of NR vulcanizate was found to be grinding of the rubber vulcanizate and subsequent mixing with a selected devulcanizing agent at 140 oC for 48 h. Degree of devulcanization was indicated by using sol-gel fractions of devulcanized rubber. Revulcanized rubber was made by using virgin rubber blend with devulcanized rubber at various ratios: 95/5, 90/10, 85/15, 80/20, 60/40, 40/60 and 20/80, and the mixture were further revulcanized. Tensile strength of the conventional revulcanized rubber (5-15 phr) was decreased by 5–10%, while an elongation at brakes was improved by 5–10% when the revulcanized rubber was prepared by the devulcanized rubber in the presence of 1 phr thiosalicylic acid. These results showed that mechanical properties of the revulcanized rubber were recovered more than 90% compared with the vulcanized rubber.