Effect of Moisture on Shape Memory Polyurethane Polymers for Extrusion-Based Additive Manufacturing

Abstract

Extrusion-based additive manufacturing (EBAM) or 3D printing is used to produce customized prototyped parts. The majority of the polymers used with EBAM show moisture sensitivity. However, moisture effects become more pronounced in polymers used for critical applications, such as biomedical stents, sensors, and actuators. The effects of moisture on the manufacturing process and the long-term performance of Shape Memory Polyurethane (SMPU) have not been fully investigated in the literature. This study focuses primarily on block-copolymer SMPUs that have two different hard/soft (h/s) segment ratios. It investigates the effect of moisture on the various properties via studying: (i) the effect of moisture trapping within these polymers and the consequences when manufacturing; (ii) and the effect on end product performance of plasticization by moisture. Results indicate that higher h/s SMPU shows higher microphase separation, which leads to an increase of moisture trapping within the polymer. Understanding moisture trapping is critical for EBAM parts due to an increase in void content and a decrease in printing quality. The results also indicate a stronger plasticizing effect on polymers with lower h/s ratio but with a more forgiving printing behavior compared to the higher h/s ratio.

Additive Manufacturing of Information Carriers Based on Shape Memory Polyester Urethane

“…However, the data points introduced for the presented QR code carriers do also cover a broad area, which in parts overlaps with the already existing data for FFF. Due to the printing result of the thin layer as evident for the substrate of the type 3 QR code carrier, a data point emerges, defining the lowest value for Z. Interestingly, this reasonably good print resolution could neither be achieved by other groups, working on shape memory polyurethanes using extrusion-based AM techniques [26,27,28,29,30,65,66] nor by other researchers who utilized those 3D printing techniques, which were described by Quinlan et al [64]. Admittedly, two-photon lithography (2PL) is another AM technology, which was not included in our considerations, but allows obtaining 3D objects, which are characterized by even smaller layer thicknesses of 0.2 to 0.3 µm [67].…”

Cellulose nanocrystals reinforced shape memory polymer cardiovascular stent

“…First of all, all the characterizations in this work were conducted in air and the stents were thoroughly dried in the vacuum oven. However, based on our group's previous work (Garces et al, 2019), the T g of SMP decreased significantly when moisture was absorbed into the matrix. It is, therefore, expected that the recovery ratio can increase significantly if the measurements are conducted in an aqueous environment, which is similar to the end-use condition of the stents.…”

3D Printed Shape Memory Polymers Produced via Direct Pellet Extrusion

“…Villacres et al [ 19 ] processed polyurethane shape memory pellets (SMP technologies) into a filament and fed this material into a FFF 3D printer to study the mechanical properties. Similar techniques of first processing SMP pellets into a filament, and then feeding the filament into a 3D printer have been examined by other researchers [ 17 , 24 ]. While fabricating samples directly from a feedstock material in pellet form has yet to be examined.…”