Using infrared opacifiers to reduce the thermal conductivity of micro and nanocellular polymethylmethacrylate

Abstract

Nanometric cells in cellular polymers leads to a reduced gaseous thermal conductivity but a relatively high heat transfer by radiation, which counteracts the previous reduction. In this work, the impact of the inclusion of graphene nanoplatelets (GnPs), in the thermal conductivity of micro and nanocellular polymethylmethacrylate is evaluated.Production parameters are optimized to produce materials with the desired cellular structure and good macroscopic quality. Nanocellular and microcellular materials containing a 2 wt% of GnPs with similar cellular structures to those obtained with the original PMMA resin are produced.Minimum thermal conductivity of 36 mW/(m·K) is obtained with the microcellular composite containing Nano 307 GnP. The inclusion of GnP block infrared radiation reducing the radiation term up to 60 %. In addition, particles modify the structural factor, leading to a reduction up to 22 % in the solid thermal conductivity. The keys to further reduce the thermal conductivity are also discussed.