The potential mechanical response of macromolecular systems—A composite analogy

A variety of macromolecular systems including crystalline and oriented thermoplastics, block copolymers, and flexibilized thermosetting resins can realistically be viewed as composite systems. This paper examines the utility of using predictive methods developed for two‐component engineering composites to predict the mechanical properties of macromolecular systems. The concepts presently available for the prediction of stiffness and expansion coefficients of short‐fiber rein‐forced plastics are reviewed with respect to their engineering accuracy in structural systems design. These techniques are then applied to predict the stiffness of a hybrid polymer system lying midway between an engineering composite and a crystalline polymer. The hybrid consists of a polymer matrix (butadiene‐acrylonitrile copolymer) reinforced with in‐situ crystallized, low‐molecular‐weight filler (acetanilide). Finally, the composite approach is applied to the prediction of stiffnesses and expansion coefficients of crystalline polyethylene as a function of volume fraction crystallinity and crystallite morphology.