Single-layer temperature-adjusting transition method to improve the bond strength of 3D-printed PCL/PLA parts

Although multi-material fused deposition modelling (FDM) has shown good progress and potential for industrial and scientific development, differences in physical and chemical properties cause weak bond strength between dissimilar materials in multi-material FDM parts. This paper proposes a single-layer temperature-adjusting transition (SLTAT) method to improve bond strength between dissimilar materials with different melting temperatures by adjusting the bonding-layer temperature. Herein, the bonding-layer temperature effects on the tensile strength of polycaprolactone (PCL)/polylactic acid (PLA) structures were investigated. PCL/PLA parts prepared with this method had 28% higher tensile strength than unprocessed parts when the bonding-layer temperature was 130 °C. Bonding mechanism was proposed to explain the failure modes of the PCL/PLA parts after tensile testing. Freeze-fractured surfaces of SLTAT-processed PCL/PLA specimens were observed to better understand the correlations between bonding-layer temperature and tensile strength. This approach is promising to apply in ordinary multi-material FDM processing without adding additional equipment or compromising dimensional accuracy.