Molecular analysis of the crystallization behavior of poly(aryl‐ether‐ether‐ketone)

The crystallization behavior, via annealing, of PEEK was investigated using FTIR spectroscopy. It was found that predominantly amorphous PEEK (e.g., quenched polymer) follows two distinct mechanisms when it is annealed. One is a lower energy relaxation process that involves the partial rotation of the ether linkages, allowing the molecular chains in the disordered phase to become better packed, and occurs from 50 to 140°C (slightly below T g ). This relaxation process is also observed by dynamic mechanical analyses. The other process is a crystallization that takes place above the glass transition, with its onset characterized by the rotation of the benzophenone linkages near T g . Isothermal crystallization kinetics data on PEEK can be described by an Avrami equation with an Avrami constant n of about 1.