メタクリル樹脂の圧縮クリープとその温度特性 : 高分子レオロジー
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概要
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Most of the studies on the linearity of creep of linear high polymers have been carried out by tension experiment within the small deformations in which the strains can simply be given by one-dimensional elongation ratios. In this research, the creep behaviours of an amorphous high polymer polymethyl methacrylate in compression are precisely investigated, using the modified Koka Flow Tester with cylindrical test pieces of various dimensions. The temperature investigated covers a wide range from room temperature to that of the rubbery state of the sample, and the initial compressive stresses σ_0 between 2.5 and 100 kg/cm^2 are used. The one-dimensionally expressed apparent strain ε_c(t), defined by (h_0-h(t))/h_0 in which h_0 is the initial height of the specimen and h(t) the height at time t, ranges from 0.5 to 45% (Fig. 1). The results are as follows : To the creep within the "critical creep time for viscous flow" as well as to the instantaneous deformation, Mooney-Treloar-Rivlin's equation for rubber elasticity is found well applicable by neglecting the effects of compression surfaces upon the internal stress distribution and merely introducing thereinto the time factor as shown by the following two formulas : [numerical formula], (1) where G_<oe> is the rigidity for the ordinary instantaneous deformation and α_<oe> the corresponding deformation ratio given by h_<oe>/h_0 (Figs. 2 and 3), and [numerical formula]. (2) Where G_c(t) is the retarded rigidity defined by the one third of the reciprocal of the creep compliance J_c(t), and α(t) the deformation ratio given by h(t)/h_0 (Fig. 4 and Table 1). The fact that these relations are applicable is expected to be a good evidence not only of the linearity of creep but also of the ideally elastic response of the specimen at each instant. Furthermore, the apparent creep compliance ε_c(t)/σ_0 vs. log t curves for different temperatures with test pieces of prescribed dimensions (Fig. 5) are superimposed by shifting along the time axis, to give a single master curve (Fig. 6). From this curve, the true creep compliance J_c(t) vs. Log t curve is calculated by using the beforesaid Eq. (2) (Fig. 7). Although these treatments of experimental data of different temperatures may be explained by the "method of reduced variables", some undeniable critisisms must be given on the analytical method of creep by the mechanical models from the experimental facts concerning the heat absorption at the creep recovery of Oppanol B 100.
- 社団法人日本材料学会の論文
- 1961-05-15