TIT# Relating Microhardness of Poly(ethylene terephthalate) to Microstructure
AUT# Santa Cruz, C.; Baltà Calleja, F. J.; Zachmann, H. G.; Stribeck, N.;
     Asano, T.
SOU# J. Polym. Sci., Part B: Polym. Phys. (1991), 29, 819-824
LOC# xv011  @selbst.ftx
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ABS# The microhardness (H) of poly(ethylene terephthalate) (PET) containing
     catalysts, as well as of PET without catalysts has been investigated. Two
     types of morphologies have been examined:  (a) structures where spherulitic
     growth is incomplete, resulting from a primary crystallization from the
     glassy state and (b) samples in which spherulitic crystallization is
     completed. It is shown that for the former materials, H is an increasing
     linear function of the volume of the spherulites and depends on annealing
     time and catalyst content. For the latter materials, H is nearly constant
     with increasing annealing temperature ($T_A$). Results are discussed
     in thelight of three principal structural factors which determine the
     microhardness behavior: (1) the volume fraction of spherulites within
     the material; (2) the value of crystllinity within the stacks of lamella,
     which turns out to be a constant; (3) the average thickness of the crystals,
     which increases slightly with $T_A$ after crystallization is completed.
     An expression which takes into account the above parameters and offers
     a description of the H of PET is proposed.