Influence of matrix polymer on deformation and morphology of injection molded immiscible blends with high interfacial contact

Immiscible blends of poly(ethylene terephthalate) (PET)/polypropylene (PP), polycarbonate (PC)/PP and PC/linear low-density polyethylene (LLDPE) were examined to study the influence of the high interfacial contact (pseudo-adhesion) on the mechanical properties and the morphology developed during elongation. The high interfacial contact resulted from the contraction difference of the two polymers during cooling from processing temperature to room temperature. It was confirmed that high interfacial contact could improve the mechanical properties of the blends. By calculation, the compressive force in the PET particles for PET/PP blends exceeded the yield stress of PET, satisfying the conditions for solid in-situ fibrillation. But scanning electronic microscopy (SEM) micrographs showed that PET particles were only slightly deformed into ellipsoids. The morphological evolution of PC/PP and PC/LLDPE blends were in line with the prediction for solid in-situ fibrillation. In addition, the factors determining the solid in-situ fibrillation of the immiscible blends were summarized: (a) the specimen has sufficient large deformation, (b) the matrix has sufficient high modulus, and (c) interfacial interactions are strong enough.