Effect of LiCl on the miscibility and crystallization behavior of a hydrophilic PP/PP-g-MAH/PA6 blend

Abstract

In order to investigate the effect of LiCl on the miscibility and crystallization behavior of polypropylene/maleic anhydride-grafted polypropylene/polyamide-6 (PP/PP-g-MAH/PA6) blends, a series of PP/PP-g-MAH/PA6 blends with different LiCl contents were prepared by using a twin-screw extruder. The phase morphology of blends, crystallization behavior, crystal forms and compatibilizing mechanism were investigated by scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC) and X-ray diffraction analysis(XRD). The results showed a small amount of LiCl could improve the miscibility of PP/PP-g-MAH/PA6 blends due to its catalysis for the reactions of anhydride of maleic anhydride-grafted polypropylene (PP-g-MAH) with the amino end groups of polyamide 6 (PA6). However, the situation was just the opposite in the presence of more than 0.75 wt% of LiCl. In addition, the hydrophilicity of polypropylene (PP) was largely improved due to the introduction of hygroscopic PA6 and LiCl. The water contact angle of PP-PA 2.25 decreased from 103° to 65° compared with pure PP. Thus this study might provide a promising route to generate polymer membranes in the wastewater treatment field.