Favorable Thermoresponsive Shape Memory Effects of 3D Printed Poly(Lactic Acid)/Poly(ε‐Caprolactone) Blends Fabricated by Fused Deposition Modeling

Abstract

acrylonitrile-butadiene-styrene (ABS)/ carbon fiber composites by FDM had both higher fiber orientation and higher molecular orientation compared to those by conventional techniques. [8] Jia et al. used FDM technology to make graphite sheets vertically oriented in polyamide 6 (PA6) polymer matrix, resulting in composites with high through-plane thermal conductivity. [9] It was reported that the performance of FDM products was closely related to their construction methods. Although FDM is one of the most popular 3D printing technologies, the 3D printing parts manufactured by FDM technology usually suffer from lack of functionality, thus limiting its application in some special fields. After the concept of "4D printing" was first proposed by a research group at Massachusetts Institute of Technology (MIT) in 2013, it has received great attention. [10] "Time" as the fourth dimension was introduced into 4D printing on the basis of 3D printing. The shape, structure and function of 3D printed products evolved over time under external stimulus (e.g., temperature, pH, water, light and pressure). [11] So, 4D printing requires additional stimulus and stimulus-responsive materials. Shape memory polymers (SMPs) are classified as the intelligent materials with low cost, low density, high recoverable strain and wide shape memory temperature range. [12] Their original shape can be recovered from a temporary shape in response to thermal stimuli. Generally, a fixed phase, a reversible phase and physically or chemically crosslinked structure are involved in such thermoresponsive shape memory behavior. [13] For the thermal stimuli, the switching temperature is always the thermal transition temperature (e.g., glass transition temperature or melting temperature) of the reversible phase. [14] Predictably, the SMPs capable of being applied in 3D printing could meet the requirements of 4D printing. To solve resource and environmental problems, replacement of the existing petroleum-based materials with renewable polymers is highly interesting. PLA and poly(ε-caprolactone) (PCL) with good biocompatibility and biodegradability are the two kinds of SMPs with broad application prospects in biomedical field. [15] In previous studies on the shape memory effects (SMEs) of PLA and PCL, their blends, copolymers and composites were mainly focused on. [16-18] Navarro-Baena et al. found that only the PLA/PCL blend with 30 wt% of PCL showed shape The shape of 3D printed products can be transformed over time, achieving 4D printing. In this work, poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blends are fabricated via fused deposition modeling (FDM). The thermoresponsive shape memory effects (SMEs) of 3D printed blends are investigated by stress-controlled dynamic mechanical analysis in tension mode. The SME mechanism is clarified in detail, along with the crystallization and melting behaviors, dynamic mechanical properties, and morphologies of PLA/PCL blends. It is confirmed that the crystallinity of reversible phase PCL, the glass transition behav...

In Situ Generation of Green Hybrid Nanofibrillar Polymer-Polymer Composites—A Novel Approach to the Triple Shape Memory Polymer Formation

“…A comparative analysis of the DMA curves shows that more effective physical crosslinking networks are formed at the interphases of a composite than at a blend, which suggests higher SME parameters, such as strain recovery and strain-fixation ratio. A critical role of physical crosslinking at the phase interfaces in shape recovery has also been reported in other studies [32,33].…”

“…A comparative analysis of the DMA curves shows that more effective physical crosslinking networks are formed at the interphases of a composite than at a blend, which suggests higher SME parameters, such as strain recovery and strainfixation ratio. A critical role of physical crosslinking at the phase interfaces in shape recovery has also been reported in other studies [32,33]. Since the glass transition of PLA takes place at 62-65 • C, it was very important for the programming of triple shape memory effect (triple-SME) that the PBAT crystallization process is completed prior to the glass-to-rubber transition of PLA.…”

Investigation of the Shape-Memory Properties of 3D Printed PLA Structures with Different Infills

“…It should be mentioned that PLA is not the only 3D printable shape memory polymer (SMP). Other SMPs which can be 3D printed are, e.g., polyurethane [ 25 , 26 ], poly(ε-caprolactone) [ 27 ], poly(vinyl alcohol) [ 28 ] or poly cyclooctene [ 29 ].…”

Pressure Orientation-Dependent Recovery of 3D-Printed PLA Objects with Varying Infill Degree

“…This means that a 3D-printed object from PLA can be deformed to a certain degree and subsequently regenerated into its original shape through heat treatment, typically in the temperature range of 60–100 °C [ 15 , 16 , 17 , 18 ]. While other 3D printing polymers, such as poly(vinyl alcohol), poly(ε-caprolactone) or polyurethane, also show shape-memory properties [ 19 , 20 , 21 , 22 ], PLA is often advantageous due to its ease of printing, the relatively low price, and especially its biocompatibility.…”