Effect of acetone extraction on elastic constants and mechanical strengths
2012
Azemi S.
Vulcanised unfilled natural rubbers containing different quantities of oil were prepared. The amount of oil was varied from 5, 10, 25, 35 and 40 p.p.h.r. The oil was later extracted by means of hot-acetone extraction. Simple extension tests were conducted to determine the elastic constants C1 and C2 before and after acetone extraction. The elastic constant C1 decreased with increasing amounts of oil due to the dilution effect. After the oil had been fully extracted, the elastic constant C1 also decreased in the order of increasing oil initially present in the rubber. Statistical theory of rubber elasticity was referred to explain the phenomenon. It was found that the Tg of the rubber was not affected very much by aromatic oil but was affected significantly by paraffinic oil. The Tg decreased with increasing amounts of paraffinic oil present in the rubber. After acetone extraction, the Tgs of the vulcanisates were the same. Tensile strength of unfilled NR did not show much difference before and after acetone extraction. In contrast, tearing energy of vulcanised black-filled NR was significantly affected by oil extraction. This work has important practical issues since the loss of oil through slow evaporation may affect the stiffness of the rubber component. In rubber engineering applications, consistency in stiffness is very important in service performance.
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