Controllable shape‐memory recovery regions in polymers through mechanical programming

Abstract

A temperature memory effect means a shape‐memory material can remember its deformation temperature. In general, a higher deformation temperature requires a higher activation temperature for shape recovery. In this work, we demonstrate that the unloading temperature can also significantly influence the shape‐memory performance. A series of shape‐memory tests are performed on Nafion while varying the loading and unloading temperatures. The results show that the loading temperature determines the final shape‐recovery region, while the unloading temperature influences the onset recovery region. We also develop a finite‐deformation viscoelastic model to investigate the above findings. The simulation results show good agreement with the experimental data, though the model predicts the recovery region occurring at a lower temperature. The model is further used to study the effects of the loading rate, unloading rate, and the holding time on the shape‐memory behaviors. The results suggest that a smaller loading rate and unloading rate and a longer holding time can shift the recovery region to a higher temperature. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45909.

Designing triple‐shape memory polymers from a miscible polymer pair through dual‐electrospinning technique

“…Shape memory polymers (SMPs), a class of stimuli‐responsive materials, are able to switch from temporary shape(s) to their original shape upon the application of specific external stimuli, such as heat, infrared light, electricity, radio frequency, alternating magnetic field, and solvent …”

Experimental investigation and modeling of the temperature memory effect in a 4D-printed auxetic structure

“…deformation temperature, deformation, holding and cooling time) and heating histories. A good agreement was found for various materials (Nafion perfluorosulfonic acid ionomer [56,57,68]; acrylate-based amorphous polymer [69]; epoxy based photo-curable resin [46]) and thermomechanical histories. Interestingly, in the works of Yu et al [56,69] a mechanistic description of the model accompanies the simulations, offering an explanation of the TME principle in terms of a different storage of stress or, equivalently, elastic strain energy in equilibrium and nonequilibrium branches of the thermoviscoelastic model.…”

“…By this point of view, materials exhibiting the TME, are not dissimilar from the most standard SMPs, but they require a finer characterization of the model parameters in order to properly describe their highly distributed thermal transition process. For this reason, a generalized Maxwell model with multiple non-equilibrium branches is often employed [46,56,57,68,69]. This approach offered the possibility of theoretically describing the response of materials presenting the TME and of predicting it according to specific programming parameters (i.e.…”

Experiments and Models of Thermo-Induced Shape Memory Polymers

“…Cui and Lendlein [13] found the switching temperature of shape recovery in the stress-free recovery, the maximum recovery stress and the corresponding temperature in the strain-constraint recovery increase with the increase of deformation temperature. The start temperature of shape recovery can be controlled by adjusting the cooling temperature during unloading [16].…”

“…Recently, the multibranch models considering the stress relaxation were developed to reasonably capture the SME of TSMPs [16,[36][37][38]. For considering more complex shape memory behaviors, Xiao et al [39] proposed a thermo-visco-plastic model at finite deformation to describe the multiple SME and temperature memory effect by introducing the structural relaxation and stress relaxation [39].…”