Inelastic Deformation of Glassy Polyaryleneetherketone: Energy Accumulation and Deformation Mechanism

The plastic deformation of glassy non-annealed polyaryleneetherketone (PAEK) was investigated via deformation calorimetry and thermally stimulated recovery of residual strain. Polymer samples were deformed at room temperature under uniaxial compression up to epsilon(def) = -(40-50)% at a rate of 0.04 min(-1). It was found that PAEK behaves in the deformation process similarly to many other glassy polymers: It stores internal energy excess at loading and contains two types of different inelastic strain carriers, namely the delayed elastic (epsilon(de)) and plastic (epsilon(pl)) strain carriers. The maximum level of the accumulated energy in PAEK reaches approximate to 8.3 J/g, which is close to those for glassy polystyrene and polycarbonate. Nearly all the deformation energy stored in PAEK is carried by the delayed-elastic strain. The carriers of plastic strain carry no extra energy or a very small amount of it. The inelastic deformation of glassy PAEK proceeds in two stages. The carriers of epsilon(de) are nucleated at the first stage of the deformation process, and the carriers of epsilon(pl) are nucleated at the second stage. It was shown that, during glassy-polymer loading, the molecular level structures carrying epsilon(pl) never appear by themselves, but appear only as a result of spontaneous reorganization of epsilon(de). In other words, the plastic deformation appears in PAEK owing to the two-step process. This situation is typical for all glassy polymers.