Effect of Interphase on Physico-Mechanical Properties

Selective sorption by the filler sorption of one of the matrix components (residual monomer, low molecular homologs, various impurities) may lead to plasticization of the boundary layers and appearance of soft interphases [115,116]. 

Macromolecular fixation on the filler surface, their orientation in the direction complanar or normal to the surface and condensation result in hard interphases [116]. 

The method used for predicting the different physical and mechanical characteristics of crystalline or glassy polymeric composites is somewhat different. Most frequently it has been proposed (cf., e.g. [118]) to introduce an extra term into the relationship between some characteristic and the composition of the material based, more often than not, on the principle of additivity of the filler and matrix characteristics and taking into account their relative volumes in the composite. This extra term is the product of the interphase volume by a characteristic other than the characteristics of either the matrix or the filler. 

In this conceptual framework it is naturally impossible to simulate the effect of the interphases of complex structure on the composite properties. A different approach was proposed in [119-123], For fiber-filled systems the authors suggest a model including as its element a fiber coated with an infinite number of cylinders of radius r and thickness dr, each having a modulus Er of its own, defined by the following equation  

The exponentials Ki and K2 in the model account for the degree of heterogeneity of the interphase layer. The ratio of these exponentials is representative, as suggested in [121], of the load transmission between the fiber and the matrix (the adhesion factor a). 

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