Some studies on the effect of solvents in ENR 60 gel content measurements
2003
Tan, K. S. | Yusof A.
ENR 60 (60 mole% epoxidised NR) produced commercially by using performic acid generated in situ by the reaction of hydrogen peroxide and formic acid had significantly higher gel content if compared to ENR 25 and ENR 50. High gel causes processing problems especially in mixing or blending. This study was carried out to understand the solubility of the rubber in solvents and the formation of gel in ENR 60. Different solvents such as THF, toluene, ethanol and their mixture were used. The gel content of ENR 25 and ENR 50 obtained in toluene was higher than that in THF. The reverse result was found in ENR 60. Gel content in ENR 60 was found to be lowest in toluene and highest in ethanol. Decrease in the gel content and increase in swelling ratio of ENR 60 in toluene was found with the addition of 0.25% to 5% ethanol. It showed that there was some interaction; though to be hydrogen bonding, between the ENR 60 polymer matrix and the solvent molecules, which was enhanced by the ethanol molecules. The formation of gel, in ENR 60 was the result of a chemical reaction and the structure of ENR 60 was polarised to a greater extent than in ENR 25 and ENR 50.
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