Abstract
Polysulfone (PSU) foams containing 0–10 wt% graphene nanoplatelets (GnP) were prepared using two foaming methods. Alongside the analysis of the cellular structure, their thermal conductivity was measured and analyzed. The results showed that the presence of GnP can affect the cellular structure of the foams prepared by both water vapor induced phase separation (WVIPS) and supercritical CO2 (scCO2) dissolution; however, the impact is greater in the case of foams prepared by WVIPS. In terms of thermal conductivity, the analysis showed an increasing trend by incrementing the amount of GnP and increasing relative density, with the tortuosity of the cellular structure, dependent on the used foaming method, relative density, and amount of GnP, playing a key role in the final value of thermal conductivity. The combination of all these factors showed the possibility of preparing PSU-GnP foams with enhanced thermal conductivity at lower GnP amount by carefully controlling the cellular structure and relative density, opening up their use in lightweight heat dissipators.
Highlights
Polysulfone (PSU) is a high performance thermoplastic with high thermal and chemical stability, excellent strength and toughness, good environmental stress-crack resistance, and inherent fire resistance [1,2]
graphene nanoplatelets (GnP) and the developed cellular structure affect the thermal conductivity values through a tortuosity factor that takes into account the complexity of the cellular structure. By considering this tortuosity factor and the relative density as fundamental parameters in the final thermal conductivity, our work shows the possibility of optimizing the thermal conductivity of PSU-GnP foams through the control of their density and cellular structure, related to the possibility of obtaining conductive foams at lower GnP amounts, for instance for lightweight heat dissipation components
Regarding the cellular structure of foams prepared via supercritical CO2 (scCO2) dissolution, which displayed slightly smaller cell sizes than foams from series 1 and series 2, the addition of GnP resulted in a slight decrease of the average cell size when compared to the unfilled PSU foam, which could be related to a barrier effect of the platelet-like GnP to the diffusion of scCO2
Summary
Polysulfone (PSU) is a high performance thermoplastic with high thermal and chemical stability, excellent strength and toughness, good environmental stress-crack resistance, and inherent fire resistance [1,2]. The high aspect ratio of carbon-based nanofillers allows the preparation of polymer-based nanocomposites with high performance and multifunctionality [15] Their addition to polymers can provide thermal and electrical conductivity at low nanofiller content, overcoming one of the major technological barriers of polymers and enabling their use in applications such as heat sinks [16] and electronic packaging [17]. Foaming could provide a viable strategy for developing tailored structures to enhance the heat dissipation efficiency of novel lightweight devices In this sense, PSU nanocomposite foams containing variable concentrations of GnP (up until 10 wt%) were prepared using two foaming methods: water vapor induced phase separation (WVIPS) and scCO2 dissolution. By considering this tortuosity factor and the relative density as fundamental parameters in the final thermal conductivity, our work shows the possibility of optimizing the thermal conductivity of PSU-GnP foams through the control of their density and cellular structure, related to the possibility of obtaining conductive foams at lower GnP amounts, for instance for lightweight heat dissipation components
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