PMMAの最大緩和時間について : 高分子のレオロジー

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It is widely known that the "box" type curve is depicted in the rubbery region of the relaxation spectrum of a linear amorphous polymer. Three parameters, τ_l, τ_m and E_0 are defined as the minimum relaxation time, the maximum relaxation time, and the height in the "box" curve function respectively. One of these characterizing factors, τ_m was shown to be the function of molecular weight and temperature in a quantitative form for polymers by Tobolsky and Andrews, and later by Tobolsky and Murakami in a more refined form. The method of obtaining the value of τ_m suggested previously by Tobolsky and Andrews, is less natural than those proposed by Tobolsky and Murakami, which is so-called Procedure X. In the previous papers, the possibility of measuring the molecular weights by Procedure X was briefly described for some amorphous polymers such as polyisobutylene, polyvinyl acetate, and polystyrene. This paper deals with such a new procedure for polymethyl methacrylate with more details. The relation among τ_m, a maximum relaxation time, n^^-_u, weight-average chain length, T temperature and T_g, glass transition temperature, or T_s, WLF temperature, or T_d, Tobolsky's temperature is indicated as follows : [numerical formula] The value of I is g, s or d, changing the values of the constants C_1 and C_2 in each case. The samples of polymethyl methacrylate whose monomers were purified by means of vacuum distillation under the nitrogen currents were prepared in the presence of varying concentration of the init8iator 2-azobis isobutyronitrile at 60℃, using lower conversion around 10%. The radical-initiated polymers thus obtained were found to have a heterogeneity index of 1. 9. If the values of logτ_m are plotted against that of logP^^-_n, the lines consisting of two straight lines are obtained, in which the slope has a value of 3.4 in the ranges of more than logP^^-_n=3.4, or about P^^-_n=2500. and has a vale of approximately unity in the ranges of less than logP^^-_n=3.4. It is interesting to consider that the knick point by two straight lines may have a close relation with the critical molecular weight M_c, though this point looks located at the place somewhat higher than M_c of polymethyl methacrylate. If the value of [numerical formula] is plotted against that of log n^^-_w, beautiful straight lines are obtained for the data including polyisobutylene, polyvinyl acetate, and polystyrene. Finally, the dependency of τ_m on temperatures is studied for polymethyl methacrylate whose slope is unity. For this polymer whose slope is unity, the following equation is obtained. [numerical formula] It is found that the experimental relation between τ_m and temperature can be on the theoretical line shown by the above equation almost exactly.
社団法人日本材料学会の論文
1963-05-15

PMMAの最大緩和時間について : 高分子のレオロジー

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