Application of a novel organic nucleating agent: Cucurbit[6]uril to improve polypropylene injection foaming behavior and their physical properties

In this study, polypropylene (PP) foams were prepared with cucurbit[6]uril (Q[6]) used as a novel nucleating agent through a microcellular injection molding foaming process. The effect of Q[6] content (0.5-2.0 wt %) on the foaming behavior, as well as thermal, rheological and mechanical characterizations of the PP/Q[6](PQ) samples were performed. According to scanning electron microscopy (SEM) images, the microstructure of foams exhibited a smaller cell size, higher cell density, and more homogeneous distribution of cells at a higher Q[6] content. It was found that the peak temperature of crystallization, the crystallinity and the crystallization rate of PP can be obviously improved by adding a low content of Q[6] (0.25-1.0 wt %), whereas further increasing the content of Q[6] (2.0 wt %) would disfavor the effect. With increasing the Q[6] concentration, the PQ composites had higher complex viscosities at low frequencies and higher modulus than that of PP except the content of 2.0 wt %. Furthermore, the introduction of Q[6] into PP can produce a mild increase in tensile strength, flexural strength and impact strength of PQ foams. This can be due to the well dispersion of Q[6], good compatibility between PP and Q[6], as well as the improvement of the cell morphology. (C) 2016 Wiley Periodicals, Inc.