Polypropylene synergistically nucleated by a novel β-nucleating and foaming nucleating agent: foaming performance and material properties

A novel β -nucleating and foaming nucleating agent (HQ[6]/EA) of polypropylene (PP) was synthesized by hemicucurbit[6]uril (HQ[6]) complexed with ethanedioic acid (EA) through the solution method. HQ[6] and EA bonded together through non-covalent bond force, and the morphology changed obviously. The maximum content of β -PP crystal form was 15.34% with 0.5% (by weight) HQ[6]/EA, and the crystallization rate and crystallinity of the nucleated PP were improved, and the decomposition temperature of PP composites was 50 ℃ higher than that of pure PP. During the injection molding process of nucleated PP foaming material, HQ[6]/EA was employed as the nucleating agent and azodicarbonamide as the foaming agent. While HQ[6]/EA was added with 0.5% (by weight), the average cell size of the foamed composite was reduced by about two times relative to that of pure PP, and the cell density was increased by about 6.5-fold. The mechanical properties of PP composited with HQ[6] and HQ[6]/EA with the loading from 0.25% to 5.0% (by weight) were examined. Among the different nucleating agents studied, HQ[6]/EA with a loading of 0.5% (by weight) exhibited a considerable improvement in the mechanical properties after comparison with pure PP. The overall enhancement of tensile properties for PP composites increased by 32.2%, the flexural strength properties increased dramatically by about 12.7%, and the impact strength increased by more than two times. Graphical abstract