Abstract
There are three difficult points in the studies on the filler reinforcement: (1) the formulation concerned with the internal deformation which must be distinct from the external one, (2) the quantitative representation of the boundary state between the filler and the rubbery medium, which is not easy of the scarcity of experimental information, (3) the formulation of the cavitation caused by elongation which is observed only in filler-reinforced vulcanized rubber.
As have already been treated in our several foregoing papers, the above mentioned difficulties may be solved as follows: the actual adhesion state is approximated by a mixed system comprising both the idealized state of perfect adhesion and the idealized state of perfect non-adhesion; a ratio of the former to the latter is (1-ζ):ζ, where ζ denotes a certain parameter characteristic of the actual adhesion state in question.
By means of this method the internal mechanism of the filler reinforcement may be understood in all the aspects, especially it is made clear that the reinforcement consists of three effects: the volume effect, the surface effect and the cavitation effect.
Although two parameters K0 (that is gf(m)/(grd), which is a ratio of the surface density to the volume density)and (1-ζ)in this theory have been hitherto determined only by the mechanical experiment, we will compare in the present study the two pairs of parameters, the parameters which are determined from the mechanical data and the ones which are determined from optical data.
The filled specimens containing various concentrations of basic magnesium carbonate as filler; X=0, 0.084, 0.168, 0.252, 0.336 and 0.42 have been examined here.
From the analysis of both experimental data by means of this theory, we have obtained the common value K0=2.3, and made clear that the degree of adhesion (1-ζ) tends towards the saturate value, already at the second elongation, in the mechanical experiment, and that the strain birefringence is independent of the repeating times and filler concentration X.
Since the isochromatic lines for the specimens having higher concentration, such as X=0.336, 0.42, are not clear and moreover the transparency of the above specimens are bad, the optical data cannot be analyzed in the present study. We are going to perfrom a more accurate study before long by the use of more transparent specimens.
This theory has been found to be comparatively satisfactory from the viewpoint also of the data of the above experiments.
