Fabrication of poly (vinyl alcohol)/graphene nanocomposite foam based on solid state shearing milling and supercritical fluid technology

Combining the nanocomposite and supercritical fluid (SCF) foaming technology develops an effective preparation method for new class of microcellular polymer nanocomposite foam, which has received much attention in both research and practice. In this paper, the poly (vinyl alcohol) (PVA)/graphene nanocomposites were successfully prepared at ambient temperature through the solid state shear milling technique, and made into foam material by using supercritical carbon dioxide as the physical blowing agent. The results indicated that graphene sheets were uniformly incorporated into the PVA matrix after milling, and graphene sheets did not reaggregate in the subsequent melting process. These well-dispersed PVA/graphene nanocomposites presented significant increases in tensile strength and thermal behavior compared to pure PVA. In the SCF foaming procedure, graphene sheets acted as the heterogeneous sites to facilitate the bubble nucleation process. More importantly, the embedded graphene sheets played an effective role of reinforcing the cell walls to stabilize the cellular structure during the cell growth stage, thus compressive properties of the nanocomposite foams were significantly enhanced. The bubbles tended to be elongated along the direction of CO2 decompression at a relatively high foaming temperature and with fast depressurization rate. (C) 2017 Elsevier Ltd. All rights reserved.