部分および完全蟻酸化ポリビニルアルコールの線型粘弾性について

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The linear viscoelastic behavior of polyvinyl alcohols, those partially formylated and those completely formylated, including stereo-regular polyvinyl formates, was investigated at various temperatures above the glass transition temperature in order to obtain the effect of successive change of polymer structure, from semi- to quasi-crystalline and to amorphous, upon its mechanical behavior and temperature dependence. The temperature dependence of the shift factor above the glass transition temperature for composing the master relaxation or complex dynamic modulus function of a basis of the hypothesis of time-temperature superposition could not be expressed by the WLF equation for the partly formylated semi- to quasi-crystalline polymers. The temperature dependence of the apparent activation energy for the relaxation process evaluated from the above temperature dependence of the shift factor showed the maximum at a particular temperature T_<s,1>, which is closely correlated, as observed in amorphous polymers, with the glass transition temperature, plus the maximum at a temperature T_<s,2> above T_<s,1> for the partially formylated polymers, which may be correlated with the crystal disordering temperature. The above anomalies suggest the existence of another type of intermolecular relaxation mechanism on the plateau of leathery consistency for the partially formylated polymers, which is probably due to loosening of crystal structure in contrast to that of merely mechanical entanglement between the polymer chains for amorphous polymers, and invalidate the hypothesis of time-temperature superposition over the range of glassy to leathery consistencies for the semi- to quasi-crystalline polymers. From the complex dynamic modulus function, mainly the loss modulus functions, two types of relaxation mechanism for the partially formylated polymers, intra- and inter-molecular relaxation mechanisms, were separated on the assumptions that the moduli are taken to be additive for assessing the contribution of each mechanism to the viscoelastic properties; the loss modulus function of each mechanism is given by a symmetric functions, such as Gaussian type, with respect to log. frequency; and the hypothesis of time-temperature superposition is valid for each relaxation mechanism, independently.
社団法人日本材料学会の論文
1967-07-15

部分および完全蟻酸化ポリビニルアルコールの線型粘弾性について

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