Effect of nanosilica and polyphosphazene elastomer on the in situ fibrillation of liquid crystalline polymer (LCP) and thermo-mechanical properties of polybutylene terephthalate (PBT)/LCP blend system

Nanocomposites of polybutylene terephthalate (PBT) and liquid crystalline polymer (LCP) with either polyphosphazene or nanosilica, or in combination of both were prepared by melt blending. The compatibility between the polymeric phases (PBT&LCP) was observed to be increased by the addition of polyphosphazene while the nanosilica promoted the LCP domain deformation from spherical to ellipsoidal shape. LCP fibres were produced in presence of both polyphosphazene and nanosilica due to the compatibilization of polyphosphazene and bridging effect of nanosilica through hydrogen bonding. All these above structural changes were confirmed by scanning electron microscope (SEM). Transmission electron microscope (TEM) images showed better dispersion of nanosilica in presence of polyphosphazene than nanosilica alone. There is remarkable increase in storage modulus with the addition of nanosilica, individually and in combination with polyphosphazene. Percentages of crystallinity for the concerned nanocomposites were calculated through X-ray diffraction study (XRD). Tensile strength and Young modulus were increased with addition of nanosilica and polyphosphazene but percentage of elongation at break was higher for polyphosphazene added nanocomposite. This is due to flexible compatibilizing effect of polyphosphazene, which delays the detachment of liquid crystalline polymer (LCP) domain from the polybutylene terephthalate (PBT) matrix and thus detains the fracture.

► Effect of polyphosphazene and nanosilica in the blend of two incompatible thermoplastics.
► Incorporation of polyphosphazene enhances thermal stability of blends but the % crystallinity reduced.
► Addition of both nanosilica and polyphosphazene increases the thermo-mechanical and crystallinity.