Towards a new generation of polymeric foams: PMMA nanocellular foams with enhanced physical properties

- PMMA micro and nanocellular foams with comparable densities have been produced.
- Micro to nano scale transition has been studied on several physical properties.
- Cell size range and the properties of the foams have been clearly related.
- Nanocellular foams have been revealed as new materials with enhanced properties.

Could the reduction of the cell size to the nanometer range yield better mechanical properties than those of microcellular and conventional foams? This study answers this question taking advantage of the unusual ability of the solid state poly(methyl methacrylate) (PMMA)-CO2 system to produce comparable bulk foams both in the micrometer and nanometer range.Several microcellular and nanocellular foams with cell sizes from 11 μm to 200 nm and relative densities about 0.5 have been produced and characterized. In particular, the cellular structure has been characterized in detail as well as the dynamic mechanical behavior, the mechanical behavior at high and low strain rates, and the shore hardness. As a result, it has been demonstrated that nanocellular foams present a significant improvement in several physical properties due to the modified cellular structure. These results confirm nanocellular foams as a new generation of polymeric foams with enhanced properties.