Effects of polyamide 6 on the crystallization and melting behavior of β-nucleated polypropylene

Non-nucleated polypropylene alloy with polyamide 6 (PP/PA6) and β-nucleated polypropylene (β-PP)/PA6 alloy, as well as its compatibilized version with maleic anhydride grafted PP (PP-g-MA) were prepared with an internal mixer. In the all alloys, PP formed a continuous phase with a dispersive PA6. Effects of PA6 on the non-isothermal crystallization behavior, melting characteristics and the β-PP content of alloys were investigated by differential scanning calorimeter (DSC) and wide angle X-ray diffraction (WAXD). The results indicated that the crystallization temperature (image) of PP shifts to high temperature in the non-nucleated PP/PA6 alloys due to the α-nucleating effect of PA6. However, in the β-nucleated PP/PA6 alloys, PA6 hardly has an effect on the image of PP. The β-PP content in the alloys not only depends on the content of the PA6, but also on the melting temperatures. It is proved by etching the alloys with sulfuric acid that the nucleating agent mainly disperses in the PA6 phase and/or the interface between PP and PA6 when blended at high temperature. Addition of PP-g-MA promotes the formation of β-PP in the β-nucleated PP/PA6 alloys. The increase in the PA6 content has a little influence on the image of PP and the β-PP content in the compatibilized β-nucleated PP/PA6 alloys. The non-isothermal crystallization kinetics of PP in the alloys was evaluated by Mo’s method.