Fabrication of lightweight, tough polypropylene composite foams: effects of nucleating agent structure on the foaming behavior and tensile property of polypropylene foams

The type and structure of nucleating agents have an important influence on the properties of the final foam as well as on the nucleation of the bubbles during injection foaming. In this study, a simple melt blending method was used to prepare polypropylene/nucleating agents (PP/NAs) composites containing nucleating agents with different structures, and the rheological behavior of the PP/NAs composites was studied using a rotational rheometer. According to the rheological data, the structure of the nucleating agent was not the primary reason for influencing polymer viscosity. Additionally, PP/NAs composite foams were prepared by chemical foaming injection molding process and the bubble dynamics, cell quality and tensile properties were investigated. The results exhibited that polymers with β-cyclodextrin (β-CD), which had a self-contained cavity-circular table structure, as the nucleating agent have better bubble nucleation dynamics. The tensile toughness of PP/β-CD foam was increased from 8.21 MJ/cm³ to 20.54 MJ/cm³, an improvement of 150.34% by comparison with pure PP foam, which was attributed to having an average cell diameter of 23.98 μm and a cell density of 2.36 × 10⁷ cells/cm³. Therefore, this study provides a reference for the design of efficient nucleating agents for the preparation of structural foam materials with lightweight and tough properties.