The crystal orientation and the microstructure of biaxially oriented polyethylene films are examined by means of wide (WAXS) and small angle X-ray scattering (SAXS) as a function of the final applied pressure. The SAXS patterns of the starting uniaxially oriented injection moulded materials, having a shish-kebab microstructure, yield two meridional maxima with long periods of 36 and ~ 50 nm. It is shown that with increasing applied compressive stresses the intensity of the initial meridional long period decreases, while a new equatorial long period appears in the normal direction to the initial orientation. This final long period only depends on the temperature of deformation. Results are discussed in terms of a gradual transformation from the original shish-kebab structure into oriented domains of the pressure-induced structure, appearing at right angles to the initial axial direction. The coexistence of microdomains, with chain and lamellar orientation at right angles to each other, yields tensile strength values in the two principal directions of the films which are larger than 100 MPa.
Посилання на статтю:
Structure formation and properties of biaxially oriented polyethylene films by compression of injected mouldings / F. Ania // Polymer. – 1992. – Vol 33. – P. 233-238.