Elastic properties of oriented polymers, blends and reinforced composites using the microindentation technique

The elastic behaviour of poly(ethylene terephthalate) (PET) and nylon 6 (PA6), their blends (1:1 by weight) and microfibrillar-reinforced composites of the previously mentioned homopolymers has been investigated by means of load-displacement analysis from indentation experiments. The dependence of the elastic modulus of the homopolymers upon the degree of crystallinity and the crystal size, as derived from indentation experiments, is discussed. A linear correlation between the elastic modulus anisotropy and the microindentation hardness anisotropy values is also found to apply for the oriented materials. The results reveal that the indentation modulus values of the PET/PA6 blends follow the parallel additivity model of the individual components. The use of the additivity law is also shown to provide a value, otherwise not accessible from direct measurements, of the modulus of the microfibrils within the microfibrillar-reinforced composites.