Influences of coagulum maturation time of rubber latex coagulated with formic acid and microorganism on the effective storage time of natural rubber
2014
Zhang, B. L. | Wang, Y. Z. | Huang, H. H.
Fresh NR latex was coagulated using formic acid and microorganism. The resulting coagula were matured at various conditions, followed by creping, size reduction and drying at 115ºC for 5 hours. The dried coagula were then scanned using differential scanning calorimetry (DSC) and aged at various ageing times at 70ºC. The effective storage time (i.e. storage life) of the coagula was evaluated through heat accelerated storage ageing combined with the Doyle-Ozawa equation and the heat ageing life equation. The results showed that the effective storage time of natural rubber prepared by the coagulum of fresh latex coagulated with formic acid and matured for 6, 12, 18 and 24 h respectively increased to 45.6 years from 23.2 years at 30ºC, and increased to 100.5 years from 46.7 years at 25ºC. The effective storage time of natural rubber prepared by the coagulum of fresh latex coagulated with microorganisms and matured for 6, 12, 18 and 24 h respectively increased to 83.3 years from 57.7 years at 30ºC, and increased to 206.3 years from 132.8 years at 25ºC. Both effective storage time of natural rubbers coagulated with formic acid and microorganism increased with the prolonging of coagulum maturation time. The effective storage time of NR from the coagulum matured for 6−12 h increased fast, the effective storage time of NR prepared by the coagulum matured for 12−18 h increase slowly and the increase in the effective storage time of NR prepared by the coagulum matured for 18−24 h tend to be flat. The effective storage time of natural rubber coagulated with microorganisms is obviously longer than that of natural rubber coagulated with formic acid in the same storage conditions.
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