COMPATIBILIZATION OF BLENDS OF POLYETHYLENE WITH A SEMIRIGID LIQUID-CRYSTALLINE POLYMER BY PE-G-LCP COPOLYMERS

The blends of thermoplastics with liquid crystalline polymers show, in general, poor properties because of the lack of adherence between the two phases. The use of ad hoc synthesized copolymers containing the m onomer units of the two polymers has been recently considered by some of us for blend compatibilization, and the results appear promising. I n this work, new PE-S-LCP copolymers, prepared either by the synthesis of the LCP in the presence of a functionalized PE, or by reactive ble nding of the latter polymer with preformed LCP, have been employed as compatibilizing additives for blends of PE with a semirigid LCP. The m orphology and the rheological and mechanical properties of the ternary blends, compared with those of samples without compatibilizers, or co ntaining conventional maleic anhydride grafted PE, indicate that the P E-g-LCP copolymers do in fact lead to an improvement of interfacial ad hesion, both in the melt and in the solid state, as well as to a modes t enhancement of the mechanical properties. The results may be rationa lized considering that the PE-S-LCP copolymers used by us consist of f airly short PE backbones with LCP grafts of various length. The molecu les with longer LCP branches are thought to become mixed at the surfac e of the LCP particles and to give rise to fairly weak interaction wit h the PE matrix. It is argued that new PE-S-LCP copolymers synthesized from higher molar mass functionalized PE samples might show much bett er compatibilizing performance.