Effects of Phase Morphology on Mechanical Properties: Oriented/Unoriented PP Crystal Combination with Spherical/Microfibrillar PET Phase

In situ microfibrillation and multiflow vibrate injection molding (MFVIM) technologies were combined to control the phase morphology of blended polypropylene (PP) and poly(ethylene terephthalate) (PET), wherein PP is the majority phase. Four kinds of phase structures were formed using different processing methods. As the PET content changes, the best choice of phase structure also changes. When the PP matrix is unoriented, oriented microfibrillar PET can increase the mechanical properties at an appropriate PET content. However, if the PP matrix is an oriented structure (shish-kebab), only the use of unoriented spherical PET can significantly improve the impact strength. Besides this, the compatibilizer polyolefin grafted maleic anhydride (POE-g-MA) can cover the PET in either spherical or microfibrillar shape to form a core–shell structure, which tends to improve both the yield and impact strength. We focused on the influence of all composing aspects—fibrillation of the dispersed PET, PP matrix crystalline morphology, and compatibilized interface—on the mechanical properties of PP/PET blends as well as potential synergies between these components. Overall, we provided a theoretical basis for the mechanical recycling of immiscible blends.