Creep behavior and shape memory performance of 4D printed PLA/PHA porous structure: influence of electrospun fiber coating

Research Overview: A study published in Polymer Testing (online on October 14, 2026, authored by Kardo Khalid Abdullah, Szabolcs Krizma, Kolos Moln á r) investigated the creep modeling and shape memory performance of 4D printed PLA/PHA porous (honeycomb) structures, combined with electrospun fiber coating. The study combines porous frameworks manufactured by additive manufacturing with electrospun fiber coatings, focusing on the deformation response of such composite structures under sustained loads and their shape recovery ability after thermal triggering.

Methods and Focus

From the perspective of research design, the work revolves around two main lines: one is to model the creep behavior of PLA/PHA honeycomb structures to describe the time-dependent deformation of materials under constant stress; The second is to evaluate the shape memory performance after coating electrospun fibers, including shape fixation and recovery. PLA and PHA are both biodegradable polyesters, and their porous structures are prone to local deformation and overall collapse of the pore walls during loading. Therefore, creep data has become a key indicator for determining the long-term dimensional stability of the structure. The electrospun fiber coating forms an additional fiber layer on the surface of the skeleton, which may alter the stiffness distribution and stress transmission path of the structure, thereby affecting the creep rate and recovery behavior.

Significance in the field of polymer aging and stabilization

Although the core of this study is mechanical modeling and shape memory function, its object and testing approach are directly related to the evaluation of polymer aging.. Creep is essentially a time-dependent viscoelastic deformation, which belongs to the same category of problems as dimensional instability and stress relaxation of materials during long-term use; For polyesters such as PLA/PHA that are sensitive to hydrolysis and thermal oxidation, the structural response reflected by creep testing is often intertwined with the decrease in molecular weight and changes in chain segment activity during degradation. The constant load creep and shape memory cycling tests used in the study can serve as supplementary means for assessing weather stability and service life, helping to determine whether porous structures experience irreversible deformation accumulation under repeated thermal mechanical cycles. From the perspective of formulation and stabilization, PLA/PHA porous materials face the risk of thermal oxidation degradation during processing and use, and usually require the introduction of an antioxidant system to suppress chain breakage and cross-linking during the melt processing stage. If this type of 4D printing structure is oriented towards outdoor or illuminated environments, the combination of HALS and UVA is common. The weather resistant and stable strategy is that HALS captures free radicals to interrupt the photooxidation chain reaction, while UVA reduces the initiation rate by shielding ultraviolet radiation. In the study, electrospun fiber coating was used as a surface functional layer, suggesting a possible path for separating stabilization function from structural function design – the coating can provide surface protection, while the substrate focuses on mechanical load-bearing. However, the feasibility of this approach depends on the interface bonding between the coating and the substrate, as well as the migration and distribution of stabilizing agents in the coating. It requires collaborative design at the level of complex systems, rather than simple stacking of single agents.

Inspiration from detection characterization

This study combines creep modeling with shape memory evaluation, which has methodological reference value for detection characterization of polymer aging. On the one hand, parameters such as time stress superposition and creep compliance can be used to quantify the effect of stabilization formula on long-term deformation.; On the other hand, shape recovery rate and recovery time can serve as sensitive indicators of structural integrity under thermal mechanical history. For PLA/PHA porous materials containing HALS/UVA complex system, it is recommended to simultaneously investigate chemical aging indicators such as molecular weight and carbonyl index before and after creep testing to distinguish the contributions of physical creep and chemical degradation.

Limitations to note

This study focuses on creep modeling and shape memory performance, and does not involve a systematic evaluation of photoaging, thermal aging, or stabilizer formulation at the abstract level. Therefore, the specific effects of HALS, UVA, or antioxidant systems in this system cannot be inferred based on this.

. When extrapolating creep data to long-term weather resistance, it is still necessary to combine accelerated aging and outdoor exposure data.

Information source:Creep Modeling and Shape-Memory Performance of 4D-Printed PLA/PHA Cellular Structures with Electrospun Fiber Coatings， Organized by Herun Chemical.