Shear‐induced fibrillation and resultant mechanical properties of injection‐molded polyamide 1010/isotactic polypropylene blends

It is feasible to control the phase morphology and orientation for immiscible polymer blends to manipulate their properties. In this paper, the blend of polyamide 1010 (PA1010) and isotactic polypropylene (iPP) (mainly at a fixed ratio of PA1010/iPP = 80/20) was used as an example to demonstrate the effect of shear on the morphology and resultant mechanical properties. After being melt blended, the injection‐molded bars were prepared via a dynamic packing equipment to impose a prolonged shearing on the melts during the solidification stage. By controlling the shear time, the structure evolution and morphological development of the blends can be well controlled. Mechanical measurement of the molded bar showed a dramatically improved tensile property and impact strength with increasing shear time. Morphological examination revealed that the iPP droplets are elongated and become thin fibrils along the shear direction with increasing shear time. The shear‐induced fibrillation, instead of orientation, is believed to be responsible for the largely improved properties of the blend, particularly for the impact strength. The toughening mechanism is discussed based on the combined effect of hindrance of crack propagation and the transferring and bearing of the load due to the existence of the fibrils. This was further proved by changing the blending ratio and using low molecular weight iPP. Finally, we propose a concept for designing blending materials with good comprehensive properties.