Study on melting and polymorphic behavior of poly(decamethylene terephthalamide)

This work describes the melting and polymorphic behavior of poly(decamethylene terephthalamide) (PA 10T). Both solution-crystallized (SC) and melt-crystallized (MC) PA 10T show double melting endotherms in DSC. The SC crystal form melts at 260–300°C giving the first melting endotherm, and meanwhile undergoes a polymorphic transition forming the MC crystal form. The subsequent melting of the MC crystal form gives the second melting endotherm at 300–325°C. This irreversible polymorphic transition is confirmed by variable-temperature WAXD and IR. Dynamic mechanical thermal analysis (DMTA) shows a glass transition temperature (T _g ) at 127°C and the presence of an α′ transition at 203°C (0.1 and 1 Hz). This transition could be confirmed by DSC and variable-temperature WAXD experiments. The α′ transition correlates with a reversible thermal process and a sudden change in intersheet spacing.