Solid‐state foaming of carbon fiber/polypropylene/nano‐CACO₃ composite using supercritical CO₂

Abstract In this work, nano‐CaCO₃ was used to improve the foamability of carbon fiber (CF)/polypropylene (PP) composite in solid‐state foaming using supercritical CO₂. The CF content was maintained at 15 wt% and four concentrations of nano‐CaCO₃ content, 1, 3, 5 and 8phr, were used. The surface of nano‐CaCO₃ was firstly treated by silane coupling agent. By the way, the properties of the nano‐composites with various nano‐CaCO₃ contents were analyzed by scanning electron microscope (SEM), differential scanning calorimeter (DSC), and torque rheometer. Before foaming, the gas absorption experiment was done using gravimetric method. Concerning on determination of the foaming conditions, it is found that 175°C and 60s were suitable as foaming temperature and time. Furthermore, we can also find that the foamed composites with 3phr nano‐CaCO₃ showed the smallest mean cell diameter and largest cell density compared with the other nano‐CaCO₃ contents under the given saturation condition. In addition, the mean cell diameter decreased while cell density increased as saturation pressure increased because of the higher gas solubility in the composites. When the saturation pressure was 25MPa, the mean cell diameter and cell density with 3phr nano‐CaCO₃ were 17μm and 2.20×10⁷cells/cm³, respectively. POLYM. COMPOS., 35:1723–1735, 2014. © 2013 Society of Plastics Engineers