Waclaw Tomaszewski of the Institute of Biopolymers and Chemical Fibres (Poland) described the uses of Phase Change Materials in regulating the temperature of buildings (in insulation) and people (in clothing). These chemicals absorb heat on melting and release it again on freezing and can be tailored to work at specific temperatures, e.g 220C for building insulation and 370C for clothing. Unfortunately the PCMs are normally supplied as microcapsules and these increase the costs of products made from them, restrict the concentration in fibre to about 10% and prevent their use in fine-fibre products such as meltblown.
In this project, 4 different PCMs (all paraffin waxes) were added to PP and pelletized. Not all the wax co-crystallized with the PP: e.g. from a 30% addition only 20% remained fixed in the polymer. Further losses occurred due to evaporation of some of the wax from some of the PCMs during melt blowing, but meltblown PP webs containing 20% PCM were produced and tested. Thermal imaging and measurements of temperature regulation factors showed that the PCMs were working as expected although the rates of heating and cooling affected their performance. They worked better with gradual temperature changes. Thermal wave propagation measurements showed that for rapid temperature changes only the PCM in the layer close to the heat source was effective.
In response to questions Mr Tomaszewski revealed that the PCM tended to be at the surface of the fibre and could be removed by washing. One questioner proposed using the PP/PCM pellets for the core of a bico fibre.