天然ゴム及び合成シス-1,4-ポリイソプレンのムーニー粘度と緩和弾性率の関係
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概要
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Relaxation moduli in the plateau and terminal zones were investigated using uncross-linked natural rubber (SMR 5L) and synthetic cis-polyisoprene (polymerised with Ziegler-Natta catalyst) of which Mooney viscosities were from 30 to 70. Stress relaxation experiments were carried out under smaller strain than 5% and at-50°C to 90°C. The relaxation moduli of both polymers could be superposed using the following shift factor, <I>a<SUB>t</SUB></I> ;<BR>log <I>a<SUB>T</SUB></I>=-8.86 (<I>T-T<SUB>s</SUB></I>) /101.6+<I>T-T<SUB>s</SUB></I><BR>where <I>T<SUB>s</SUB></I> =-25°C. The reduced relaxation moduli of natural rubber were higher than those of synthetic cis-1, 4-polyisoprene in the same Mooney viscosity. Measurements of limiting viscosity number and zero shear viscosity showed that natural rubber had higher mean molecular weight than synthetic cis-1, 4-polyisoprene in the same Mooney viscosity. Schlieren patterns by ultracentrifuge showed that natural rubber had broader molecular weight distribution than synthetic cis-1, 4-polyisoprene in the same mean molecular weight.