Thermal effects in blasting and erosion of polymeric materials

The application of solid particle blasting has been investigated as a means for the removal of coatings from polymeric substrates for reuse and recycling. Experimentally, it has been observed that during particle blasting, substantial temperature rises are observed in the polymer substrates, even when the blast media is solid carbon dioxide at less than −78.5 °C. Such temperature rises are not seen in metallic materials subjected to the same blasting conditions. A model has been developed which allows such observations to be understood. It is shown that temperature rises in polymers are associated with their low thermal conductivities and the relatively deep plastic zones (associated with their low hardnesses) which are associated with the regions in which the energy of impact is dissipated as heat. When the impacting particles are not prone to fragmentation, around 70% of the incident kinetic power of the jet is transformed into heat. The temperature increases predicted by the model are in good agreement with experimental data for both metallic and polymeric substrates when impacted with robust glass-beads. However, the model is not able to predict the behaviour of the polymer when impacted by the friable solid carbon dioxide particles. In this case, it is shown that agreement can be forged if the fraction of kinetic power transformed into heat is reduced to around 1%. This substantial reduction can be justified on the basis of almost complete fragmentation of the solid carbon dioxide particles upon impact.