Analysis and characterization of influence of PLA printing parameters on 4D printing retention time under thermal stimulus

Abstract

The precise recovery of 4D printed smart materials to their permanent shape requires effort and time due to limitations in post-printing characterization. Several studies have used matrices of different fillers and artifact designs to address this, but these approaches restrict the potential of smart morphology. This paper focuses on combining a preprogrammed model with characterization study of different 4D printed polylactic acid (PLA) materials under thermal stimuli that can address the brittleness, toughness, and rigidity of PLA. In parallel, the study pursues the influence of predesigned printing thickness parameters for a mechanical engine thermostat valve, used as a case study. The dynamic structural behavior of PLA was first examined using a predesigned model subjected to a time-dependent thermal stimulus. The samples were prepared from pure PLA classified as Tough black, Faster white and Creality blue PLA. Independent of filament color, the investigation was intended to clarify how a layer architecture constrains deformation magnitude and application range. Mechanical tests showed that the three PLA variants achieved a tensile strength of 33.48 MPa, 29.13 MPa, and 33.45 MPa, respectively while conventional PLA has an allowable tensile strength of 60 MPa. Differential Scanning Calorimetry (DSC) analysis revealed an endothermic peak of 9.09 J/g and an exothermic peak of 6.41 J/g. The thermal actuation tests demonstrated a shape recovery of 6 mm within 2 s under thermal stimulation, confirming thermally driven rapid deformation behavior. Scanning Electron Microscopy indicated that CR-PLA possessed the highest pores/void, followed by Tough PLA. However, optical microscopy conducted after DSC thermal cycling showed interlayer erosion, particularly in Faster PLA and Tough PLA, suggesting reduced interlayer bonding after heat exposure. Overall, Faster PLA showed the best interlayer adhesion and dynamic response without post-processing, whereas CR-PLA required post-printing adjustment due to increased rigidity. � 2026 The Authors