Effect of blend ratios and printing parameters on PLA/TPU shape memory polymer performance

The advancement in soft robotics and intelligent systems has triggered interest in PLA/TPU shape memory polymer, due to their promising combined properties and the coupling effects that enable the development of flexible and dynamic robotic systems. Additive manufacturing (AM) printing parameters are known to directly affects shape memory performance of PLA/TPU. The effect of AM printing parameters on shape memory performance, commonly measured from the shape recovery ratio (R r %) and shape fixity ratio (R f %), has not be extensively studied and thus, not well understood. This study investigates the combined effects of TPU content and key printing parameters on both shape memory performances. Six blend ratios comprising pure PLA, and PLA/TPU ratio by weight of 90/10, 80/20, 70/30, 60/40 and 50/50 were selected and evaluated. Taguchi L9 orthogonal array experimental design was employed and four printing parameters which are printing speed, raster angle, layer thickness and printing temperature were selected. The results show that increasing TPU content reduces both R r % and R f % and pure PLA exhibits the highest value for both cases. Next, among the printing parameters, layer thickness and printing temperature were found to be most and least influential factors for R r % respectively. In terms of R f %, the parameters with highest and lowest impact are raster angle and printing speed respectively. However, ANOVA analysis results confirmed that the printing parameters had minimal and statistically insignificant effects on R f %. Confirmation experiments using optimized parameters revealed that the specimens printed using the generated printing parameters can mainly enhance the R r % values with the highest increment of 3.975%. This work provides insight and guidance on the influence of AM printing parameters on shape memory performance of PLA/TPU shape memory polymer, which is critical in robotics and intelligent systems. • Shape recovery ratio (R r %) dropped as TPU content increased due to less energy storage and TPU’s elasticity that released some internal stress after processing. • Shape fixity ratio (R f %) also decreased as TPU content increased because its flexibility reduced the specimen’s ability to hold the temporary shape. • Layer thickness has the greatest influence on Shape recovery ratio (R r %), followed by raster angle, printing speed, and printing temperature. • ANOVA also showed that printing parameters had insignificant effects with R f % changes mainly caused by blend ratio differences rather than processing conditions. • Most of the specimens printed according to optimal parameter combinations produced better R r % compared to specimens printed based on Taguchi’s orthogonal array.