INFLUENCE OF MORPHOLOGY ON THE MICROHARDNESS OF POLY(ETHYLENE NAPHTHALENE-2,6-DICARBOXYLATE)

The microhardness (H) of poly(ethylene naphthalene-2,6-dicarboxylate) (PEN) with a wide range of crystallinities, spherulitic morphologies a nd different lamellar periodicities has been determined. The influence of the temperature and time of crystallization from the glassy state upon the microhardness values has been examined. For structures where primary crystallization is incomplete, it is shown that H increases li nearly with the volume fraction of spherulities. For materials where p rimary crystallization is completed, H depends on the crystallization temperature and appears to be a function of both the crystallinity and the crystal size. The results are discussed in the light of theoretic al predictions of hardness.