Annealing of polymers in the solid-melt region. I. A new approach to estimate the equilibrium melting temperature of polymer crystals

An annealing scheme for semicrystalline polymers is presented whereby a polymer is annealed in its solid-melt region, leading to crystals approaching the equilibrium crystals in terms of melting temperature. The annealing data is mathematically treated to estimate the equilibrium melting temperature (T⁰_m) of polymer crystals. As is the case with any extrapolation procedure, there are minor shortcomings with our approach, but these are far outweighed by the advantages; the latter are exemplified by a comparison with the widely used Hoffman-Weeks method for estimating (T⁰_m). The validity of our annealing scheme for the estimation of (T⁰_m) is demonstrated by analysis of well-studied polymers such as nylon 6, polyethylene terephthalate (PET), polyethylene (PE), polypivalolactone (PPL), and polytetrafluoroethylene (PTFE); other polymers studied include polyether ether ketone (PEEK) and nylon 4,6.