Melt crystallisation of polymer materials: The role of the thermal conductivity and its influence on the microstructure

Even though many characteristics of the quiescent crystallisation process o f polymers have been deeply investigated in the long run, some subjects are still open. Indeed, the theory of nucleation and growth, originally develo ped for metals and low molecular weight materials, have been extended to po lymers without taking into account all the characteristics of macromolecule s that can induce a crystallisation behaviour different from that of atoms or small molecules. This paper, within the framework of nucleation and grow th, reviews the main aspects of the crystallisation process of polymers and discusses its influence on the microstructure, also in comparison with met allic and ceramic materials. Additional factors, often neglected, affecting the crystallisation process have been also identified. In particular, cons ideration is given to heat flow from solid to melt during polymer crystalli sation that can provide an explanation for modified spherulitic morphologie s found in fibre based composite materials and blends. Moreover, the circum stances under which thermal gradients within polymer samples may play a dom inant role in crystallisation are underlined. Finally, several examples of polymer textures, that could have been originated by heat transfer anisotro py inside samples, are shown. (C) 2001 Kluwer Academic Publishers.