Study into the recyclability of a thermoplastic polyurethane powder for use in laser sintering

Previous studies into the use of polymer powders such as Nylon-12 for laser sintering have shown part property degradation caused by repeated heating and cooling. This research investigated the recyclability of a new thermoplastic polyurethane powder in the laser sintering process. The work has novel value as there has been no previous work on processing this material by laser sintering. A virgin powder sample was retained, along with a sample after each of four laser sintering builds. Each sample's recyclability was investigated by particle size analysis, differential scanning calorimetry, hot stage microscopy of particle pairs, melt flow index, tensile test sample manufacture and tensile testing. Upon recycling, no significant trend in the elastomer particle size distribution was identified, and thermal properties were unchanged, as shown by differential scanning calorimetry analysis. Hot stage analysis showed that recycling had no clear effect on sintering time. Melt flow index results showed a small increase in flow rate upon recycling, corresponding to a slight drop in viscosity, suggesting reduced chain length. The outcome of tensile tests showed a minor decrease in strength while elongation at break and Young's modulus showed a negligible decrease. The results have shown the possibility of recycling the thermoplastic polyurethane bed powder several times through the laser sintering process without any significant degradation or reduction in properties.