In‐Situ Fibrillation of Ny6/6 During Processing of PP/Ny6/6 Blends, Slightly Below the Ny6/6 Melting Temperature

Abstract

The focus of the present research is on in‐situ fibrillation of a dispersed minor phase during processing of binary immiscible polymer blends. This structured morphology is attained by extrusion compounding and injection molding at a temperature slightly below the melting temperature (Tm) of the dispersed phase, yet, well above the melting temperature of the matrix. Binary polypropylene/nylon‐6/6 [PP/Ny] blends were compounded (twin screw extruder) and processed (injection molding) both slightly below and above the Ny Tm under different blending conditions. To study the processing‐structure‐property relationships the blends were characterized using scanning electron microscopy (SEM), high resolution scanning electron microscopy (HRSEM), differential scanning calorimetry (DSC), X‐ray diffraction (XRD), and tensile mechanical behavior. Compounding and processing slightly below the Ny Tm resulted in Ny fibrils formation throughout the specimens' volume, as opposed to spherical/ellipsoidal Ny particles observed in the melt processed blends. The initial extrusion‐compounding stage has an important role in attaining Ny fibril morphology in the subsequent injection molding step, where further fibrillation takes place. The additional stretching of Ny fibrils results in the formation of highly ordered Ny crystals, having a higher melting temperature than the regular Ny crystallized from the melt, and some degree of crystal orientation. The morphology of the binary blends can be explained by the “capillary instability” mechanism and examining the relation between the time required for fibril breakup and the residence time in a die. The Ny fibrils' orientation along the applied load direction contribute to enhanced strength and modulus displayed by the 260°C injection‐molded blend compared with the blends molded at the other temperatures.