Properties of in situ composites based on semiflexible thermotropic liquidcrystalline copolyesteramide and polyamide 66 blends

Liquid crystalline polymer-polyamide 66 (LCP/PA 66) blends were compounded using a Brabender mixing followed by compression moulding. The LCP employed was a semi-flexible liquid crystalline copolyesteramide based on 30 mol% o f p-amino benzoic acid (ABA) and 70 mol% of poly(ethylene terephthalate) (P ET). The in situ composites were investigated in terms of thermal, dynamic mechanical, morphological and rheological properties. The differential scan ning calorimetry (DSC) results showed that the inclusion of the semi-flexib le LCP into LCP/PA 66 blends retards the crystallization rate of PA 66. Fur thermore, the melting temperature, the crystallization temperature and the degree of crystallinity of PA 66 were reduced considerably due to LCP addit ion. On the basis of DSC and dynamic mechanical analyses (DMA), PA 66 and L CP components of the blends were miscible in the melting state, but is part ially miscible in the solid state. Hot-stage optical microscopy examination reveals that the LCP microfibrils with random orientation are formed in th e PA 66 matrix of compression moulded LCP/PA 66 blends. In addition, the LC P domains within the PA 66 matrix deformed microfibrils, and oriented along the flow direction under the application of shearing force. The formation of microfibrils resulted in an increase in the storage modulus. Finally, th e viscosity-concentration curves of the LCP/PA 66 blends exhibited an appar ent maximum at 2.5 wt% LCP content, thereafter, the viscosity fell dramatic ally with increasing LCP concentrations.