結合脂肪酸の影響 [in Japanese] CRYSTALLIZATION BEHAVIOR OF NATURAL RUBBER, PART 2 EFFECT OF LINKED FATTY ACID ON THE CRYSTALLIZATION OF CIS-1, 4 POLYISOPRENE [in Japanese]
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The effect of fatty acid linked to <i>cis</i>-1, 4 polyisoprene on the crystallization of polymer chain was investigated by differential scanning calorimetry (DSC) and dilatometry at -25°C. Synthetic <i>cis</i>-1, 4 polyisoprene (IR) was esterified with stearic acid selectively at 3, 4 isoprene units after introduction of OH group by hydroboration (IR-C 18). The rate of crystallization of IR-C 18 was increased by the addition of saturated fatty acids. The addition of methyl linoleate promoted the crystallization of IR-C 18, whereas it suppressed the crystallization of IR. This was explained to be due to a synergistic effect of mixed and linked fatty acids on the crystallization of IR. Stearic acid was introduced into natural rubber (NR) by esterification after purification of NR by deproteinization followed by acetone extraction and transesterification with NaOCH<sub>3</sub>. The content of stearic acid in the esterified NR (DPNR-C 18) was about 1/2 compared to the ester content in untreated NR. The rate of crystallization of DPNR-C 18 was similar to that of DPNR-TE and was not increased by the addition of methyl linoleate. Precooling of the rubber at 0, 10 and 30°C before crystallization at -25°C resulted in a significant difference in the crystallization rate between untreated NR, DPNR-TE and DPNR-C 18, where the crystallization of only untreated NR was promoted by precooling. This demonstrates the presence of a critical concentration of linked fatty acid on the crystallization of NR, at which the synergistic effect was promoted with mixed fatty acids.
GOMU 72(5), 294-300, 1999-05-15
THE SOCIRETY OF RUBBER SCIENCE AND TECHNOLOGYY, JAPAN