Nanostructured Calcium Silicate Phase Change Materials for Thermal Buffering in Packaging Applications

摘要

This paper reports the development and use of a nanostructured calcium silicate - phase change material to provide thermal buffering in packaging applications. Nanostructured calcium silicate (NCS) is a proprietary new material comprising nanosize platelets stacked together in an open framework structure with a particle size of about 1 -5 microns. The material has a high pore volume and hence liquid absorbency of up to about 500 g oil 100g~(-1) silicate. Phase change materials (PCMs), typical examples of which are alkane paraffins, absorb and release heat energy (latent heat) associated with the liquid-solid transition at their melting point. The major practical problem of containing the liquid phase on melting has been overcome by incorporating these alkane PCMs into the porous NCS structure in amounts of about 3-4 times the weight of the NCS. The resulting NCS-PCM composite remains as an easily useable powder above the alkane melting point and can be readily incorporated into packaging materials to provide heat buffering properties of about 110 kJ kg~(-1) of NCS-PCM composite. This has been demonstrated by filling plastic bubblewrap bags with a NCS-PCM composite containing a Rubitherm RT6 paraffin as the phase change material with a meltimg point of about 6 °C, and using them as liners in a paperboard package. As the package is cooled the PCM in the NCS-PCM-RT6 liner solidifies and as the package is warmed up the PCM melts. Hence the NCS-PCM-RT6 liner maintains the inside temperature of the package below about 10 °C for about 110 minutes longer than without the NCS-PCM-RT6 thermal buffering liner.