Determination of orientation parameters in drawn films of thermotropic liquid crystalline polymer/polypropylene blends using WAXS

摘要

The effects of composition and compatibilizers on the molecular orientation in thermotropic liquid crystalline polymer (TLCP)/PP in situ composites films have been investigated using wide angle X-ray scattering (WAXS) techniques. The degree of preferred orientation for each component was evaluated using a novel separation technique based on a description of the scattering through spherical harmonic functions. The evaluated orientation parameters (P_2) and (P_4) of TLCP phase were found to increase up to 0.76 and 0.53, respectively, with increasing TLCP content and film draw ratio. In contrast, the PP component in all films exhibits a very low orientation ((P_2) approx 0.01) i.e. essentially isotropic. The PP component exhibits the so-called smectic phase which can be transformed to the more stable crystalline phase (alpha-form) by annealing at 110 deg C for 2 h, with a small increase in the level of preferred orientation. The inclusion of particular polystyrene-based compatibilizers was observed to have a substantial effect on the modulus of the composite and in some cases this is reflected in the level of preferred orientation in the TLCP. We deduce that the orientation parameters are largely insensitive to the fibril morphology once a certain aspect ratio has been exceeded.