Micro injection molding parameters impact on thermoplastic polyurethane (TPU) 's mechanical properties

This study focuses on investigating the effects of micro-injection molding (µm) parameters on the mechanical properties of thermoplastic polyurethane (TPU). Injection speed, injection pressure, cooling time, and plastification temperature were varied to assess their impact on the tensile testing of two TPU grades: Rx70A and EG-80A. Simulations in Moldflow predicted complete cavity filling in 1 s with 30.25 MPa injection pressure and 204.3 °C melt temperature, achieving 100% part quality after increasing cooling from 8.3 s to 9.5–12 s, reducing shrinkage from 11% to ~ 6.38%, resulting in uniform flow, no air entrapment, and weld lines only at top cavity edges. Our findings indicate that higher plastification temperatures from 190 to 200°C enhance both the elastic modulus, from 2.592 ± 1.40 MPa to 3.030 ± 0.003MPa, and yield strength from 0.030 ± 0.007 MPa to 0.042 ± 0.007 MPa, but may reduce the elasticity of Rx70A from 1663.048 ± 11.49% to 1565.34 ± 29.9% over the original length. The EG80A material’s performance is also influenced by the increase in injection temperature from 200 to 210°C, which promotes an increase in Max E (from 1353.21 ± 14.8% to 1679.34 ± 80.96%), a decrease in UTS from 21.73 ± 0.25 MPa to 19.76 ± 0.08 MPa, and an increase in yield strength (0.092 ± 0.047 MPa to 0.164 ± 0.028 MPa) and Young’s modulus (from 4.00 ± 0.25 to 4.34 ± 0.08 MPa).