Design of Shape Memory Thermoplastic Material Systems for FDM-Type Additive Manufacturing

Abstract

The work presented here describes a paradigm for the design of materials for additive manufacturing platforms based on taking advantage of unique physical properties imparted upon the material by the fabrication process. We sought to further investigate past work with binary shape memory polymer blends, which indicated that phase texturization caused by the fused filament fabrication (FFF) process enhanced shape memory properties. In this work, two multi-constituent shape memory polymer systems were developed where the miscibility parameter was the guide in material selection. A comparison with injection molded specimens was also carried out to further investigate the ability of the FFF process to enable enhanced shape memory characteristics as compared to other manufacturing methods. It was found that blend combinations with more closely matching miscibility parameters were more apt at yielding reliable shape memory polymer systems. However, when miscibility parameters differed, a pathway towards the creation of shape memory polymer systems capable of maintaining more than one temporary shape at a time was potentially realized. Additional aspects related to impact modifying of rigid thermoplastics as well as thermomechanical processing on induced crystallinity are also explored. Overall, this work serves as another example in the advancement of additive manufacturing via materials development.

Characterisation of the shape memory effect of PET polymer by FFF 3D printing

“…According to the loss modulus, the upper limit of the Tg range is 81.90°C. Usually, for shape memory polymers, the upper limit of the Tg is given by the tan δ modulus [10], because it is higher than the others. For the chosen blend of PET, the resulting tan δ modulus Tg value lies between the previously mentioned temperatures.…”

“…The sample deformation was made at room temperature in two testing cycles compared to the standard testing procedure. Shape memory specimens' cold deformation is documented in the literature [10,16,17]. The results show PET shape recovery is possible even after two cold deformation cycles.…”

“…This one uses a more rigid component to "remember" the permanent shape and a softer one for the temporary shape. The third is the partial transition mechanism which uses a mixture of materials to provide the transition phases [8][9][10].…”

Evaluation of shape memory effect in PLA/copolymers blends

“…The modulus of the binary and ternary blends remained constant, indicating that the copolymers restricted the cold crystallization of PLA. The transition temperature determined is used as the switch temperature for programming and recovery of the shape memory polymer system 70 . Easy programming (shaping) at T > T g , high resistance to deformation at T < T g , as well as rapid recovery speed at T g 71 .…”

“…The transition temperature determined is used as the switch temperature for programming and recovery of the shape memory polymer system. 70 Easy programming (shaping) at T > T g , high resistance to deformation at T < T g , as well as rapid recovery speed at T g . 71 For this particular blend system, the PLA is the continuous phase, shaping and fixing the temporary shape.…”