A basic study of orientation in poly(ethylene terephthalate) stretch‐blow molded bottles

A series of stretch‐blow molded poly(ethylene terephthalate) bottles were investigated using measurements of birefringences (in plane and out of plane) and wide angle x‐ray diffraction (WAXS) pole figures. Both bottles prepared in our laboratories and commercial bottles were investigated. Birefringences Δ n 13 and Δ n 23 of inside and outside surfaces of bottles were determined as a function of position along the length of the bottle (1‐bottle axis, 2‐hoop direction, 3‐thickness direction). The Δ n 13 , Δ n 23 for the inside surface of the bottles were found to be greater than those for the outside surface indicating heterogeneity through the thickness of the bottles. The WAXS studies indicate that the benzene rings in the polymer align parallel to the bottle surface. The chain axis in crystalline regions exhibit orientations close to equal biaxial orientation. Both Δ n 13 and Δ n 23 increased with inflation pressure.