Abstract
In order to ascertain the dynamic viscoelastic behavior of baked coating films during deformation process at a room temperature, the frequency dependence of rigidity modulus G and viscosity η of the films are measured by using a torsional pendulum of improved design consisting of a horizontal steel rod with two equal load disks fixed symmetrically with respect to the rod center at which the lower end of a sample film strip is attached. As the samples, phenol-cresol formaldehyde resin films of thermo-setting type unplasticized and plasticitized with P. V. B. or Epon _??_1009 and Fuji film of thermo-plastic type for the sake of contrast are used. The period of the pendulum is varied within the range of 1.5-17 sec. by shifting the load disks. The frequency dependence of G and η at 20_??_21°C is found as follows:
(1) With all the film examined, G values remain nearly constant but η values change considerably.
(2) η-period relation of Fuji film is of an approximate straight line passing through the origin whereas that of all the other films are of curves of third degree intercepting 7) axis.
(3) η-period relation for all the films is explained satisfactorily by the model of Voigt 4 elements.
(4) The relaxation time τ2=η2/G2 of films plasticized with P. V. B. or Epon _??_1009 is longer than that of unplasticized although η2 and η3 values of the former are smaller than those of the latter.
