An improved model for crystalline orientation of spherulitic polymers

A model is proposed to account for the orientation of crystals in spherulites upon deforming a polymer. The model assumes affine deformation of the spherulite accompanied by three processes of crystal reorientation within the spherulite. These are tilting of molecular chains with respect to the plane of the lamellae, characterized by a parameter K , twisting of the lamallae about the spherulite radii described by η, and rotation of the b crystal axis about the c axis characterized by a third parameter, P . Values of these parameters are fitted to measured orientation functions and compared with experimental measurements of the azimuthal variation of the intensities of the 110 and 200 crystal reflections from low‐density polyethylene. Good agreement is found between the experimental and theoretically predicted intensity variation. Time‐dependent experiments under relaxational and vibrational conditions are also treated by the theory.