ポリプロピレンフィルムの弾性力の温度依存性
1966 年 22 巻 4 号 p. 143-148
詳細
1966 年 22 巻 4 号 p. 143-148
Granular polypropylene polymer dissolved in toluene was spread on glass plate and after the evaporation of the solvent the polymer was melted at 180°C and then supercooled. From this sample the spherulitic film (larger part is consisted of spherulite) was obtained after the heat-treatment for 100 min. at 130°C. Drawn film was prepared by stretching the spherulitic film at the speed of 110%/min. at 130°C. The effects of the temperature on the stresses of these two kinds of films were examined under equilibrium conditions.
(1) Restoring forces, f, developed in the range of less than 2% lower elongation consist of two parts of contributions, that is, enthalpy term, and correction term on the length at varying temperatures. Entropy term at constant length, which may be considered due to the change in molecular configurations, may be neglected. Thus the expression between the restoring force and the temperature may be expressed: where l is length, β the coefficient of linear expansion of the film, P pressure, f stress, H enthalpy, γ elongation and T temperature.
(2) Both the spherulitic and drawn films, which are equal in crystallinity, obey the linear relation between stress and temperature cited above. Deviation observed above 80°C become more serious in the drawn film than in the spherulitic one. This may be caused by any transition of crystalline parts. The abrupt deviation observed in drawn film may be due to the orientation of molecular chains in the drawing process.
