Morphology Of Nanocomposite Foams Research Articles

Microstructure, mechanical and electrical characterizations of bimodal and nanocellular polypropylene/graphene nanoplatelet composite foams

In this work, linear and branched polypropylene (PP)/ graphene nanoplatelet (GnP) composite foams were prepared using supercritical CO2. The morphology of nanocomposite foams was imaged on SEM. Branched PP foams revealed bimodal cellular morphology, while linear PP exposed nanocellular structures. The effect of cell modality and adding GnP on the mechanical and electrical properties of nanocomposite foams were investigated. Addition of GnP to linear PP decreased cell density and made cell distribution uniform due to its functionality of crystal nucleating agent While in branched PP foams, it was seen by the dynamic observation that GnP acted as bubble nucleating agent, resulting in a fine cell size and increasing the foam density. Nanocellular foams exhibited better mechanical properties than bimodal but the limited expansion ratio. However, some bimodal foams presented comparable mechanical properties to non-foamed samples, in spite of high expansion ratio. Addition of graphene nanoplatelet to some extent improved the specific tensile modulus and strength of foams. The electrical conductivity of composites was reduced by foaming. However, this reduction was very significant in the case of bimodal foams.

Influence of Surface-functionalized Graphene Oxide on the Cell Morphology of Poly(methyl methacrylate) Composite

The surface chemistry of filler is closely related to the structure and morphology of nanocomposite foams. Changing the property of filler is widely used to control the cell structures and functionalize the composite foams. Surface-functionalized graphene oxide (GO-ODA) was prepared by grafting octadecylamine (ODA) on the surface of graphene oxide (GO) to make the filler disperse better in the nanocomposites and have a strong interfacial interaction with polymer matrix. Poly(methyl methacrylate) (PMMA)/GO-ODA nanocomposite foams were obtained by solution blending and foamed using supercritical carbon dioxide (scCO2). Compared to neat PMMA and PMMA/GO samples, the PMMA/GO-ODA nanocomposite foams showed improved cell structures with smaller size, higher cell density and more homogeneous distribution, which should be attributed to the heterogeneous nucleation caused by well-dispersed GO-ODA nanosheets. This work not only improved the compatibility and interfacial interaction of GO with polymer matrix but also indicated that the modified GO sheets can act as ideal filler to control the cell density, size and size distribution efficiently.