The heat capacity of poly(oxymethylene) as a function of crystailinity

Abstract

The heat capacity of several poly(oxymethylene) (POM) samples with crystallinities between 50 and 80 per cent are determined by DSC in the solid (−100 to 70°C) and liquid state (170 to 240°C). Linear relationships between heat capacity and crystallinity are found, if premelting phenomena are excluded. The heat capacities of crystalline and liquid POM are obtained by extrapolation. They differ from the hitherto recommended data. Above the glass transition region the extrapolated heat capacity for zero crystallinity agrees with the heat capacity of the melt extrapolated to lower temperatures. This is in contrast to recent results of Suzuki et al., who assume the existence of a rigid amorphous fraction which does not contribute to the glass transition.