A unified view of polymer chain orientation in complex orientation state

A general view of polymer chain orientation for fabricated polymer products which have complex states of orientation is investigated, by means of refractive index, infrared absorption, and wide angle x-ray diffraction measurements. The polymer processes focused on the skew stretching of films and injection molding for polycarbonate, poly(ethylene terephthalate), and high density polyethylene. For the determination of the principal/symmetry axes of orientation, an ellipsoidal representation for the second-order tensorial quantities was applied. In particular, a second-order tensorial quantity from wide angle x-ray diffraction pole figures was developed.;The complex chain orientation state of injection molded parts showed that the direction of the major principal axes was not uniquely in the flow direction but skewed to it. The behavior of the directions of principal axes and associated principal birefringences of polycarbonate was interpreted by the superposed effects of flow induced and thermal quenching stresses. The wall region exhibited biaxial orientation and the intermediate region, if orientation exists, uniaxial orientation character. For high density polyethylene, the major principal axis was closer to the flow direction compared with polycarbonate, which might be explained in terms of chain rearrangement during crystallization. The general behavior of crystalline orientation showed typical b-axis orientation along thickness direction, and c- and a-axes biaxial orientation in a flow-width plane.;A phenomenological approach for establishing the relationship between the chain orientation of a crystalline polymer and that of its melt prior to the onset of crystallization is proposed. This is based on a quasi-linear anisotropic relationship between two orientation tensors for the melt and the crystallized states, respectively.;The complex chain orientation state of skew stretched films showed that the major principal axes tend to move toward the second stretching direction with increasing second stretch ratio. The chain orientation state of skew stretched films exhibited biaxial behavior at low second stretch ratios, and increasing uniaxial orientation at high second stretch ratios. The mechanical properties of these films were found to be linearly related to their chain orientation state.