Optimization of the shape memory effect in shape memory polymers

Abstract

In this article, we show that given a thermoresponsive shape memory polymer, it is possible to alter a number of its properties, such as the recovery temperature, shape fixity ratio, maximum recovery stress, and final recovery stress (and even a right combination of some of them, e.g., the maximum recovery stress and final recovery stress), simply by means of selecting the programming temperature to achieve optimized performance. Some concerns for the implementation in real engineering practice are also discussed. Although the focus is on the case of a fixed maximum strain in programming, alternative programming approaches can be investigated in a similar way for optimized performance as well. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Mechanisms of the Shape Memory Effect in Polymeric Materials

“…[4,7,9,10,25,37,43,139,148,149], based on the principles of the above discussed working mechanisms, the performance of existing materials can be optimized by means of controlling the processing parameters in programming [113,126,150]. Figure 30 illustrates the influence of the programming temperature on shape fixity ratio (R f ) and shape recovery ratio (R r ).…”

“…However, recent study reveals that in the case of shape recovery without applying any constraint (free recovery), the maximum shape recovery occurs at around the programming temperature, i.e., a significant shape recovery occurs when the material is heated to the programming temperature, or to slightly above the programming temperature (refer to Figure 18). This new form of the TME provides a simple way to fine-tune the transition temperature to be within a very sharp temperature range [125,126]. Figure 18.…”

Development of high shrinkage polyethylene terephthalate (PET) shape memory polymer tendons for concrete crack closure

“…2,5,6 A key parameter which determines the final stress achieved is the temperature at which the SMP has been programmed, and the maximum value for the stress upon reheating generally occurs at or near the programming temperature initially used. 3,7 The restrained shrinkage stress also depends upon the programming strain and strain rate. 3,7 The magnitude of the restrained shrinkage stress is positively correlated with the energy stored by the SMP during deformation, and is limited by the relatively low elastic modulus of the material in the rubbery state (above Tg).…”

“…3,7 The restrained shrinkage stress also depends upon the programming strain and strain rate. 3,7 The magnitude of the restrained shrinkage stress is positively correlated with the energy stored by the SMP during deformation, and is limited by the relatively low elastic modulus of the material in the rubbery state (above Tg). Efforts to improve the rubbery state elastic modulus have included increasing the cross-linking density and the incorporation of fillers into the polymer matrix.…”

Advanced Shape Memory Technology for Comfort Fitting

“…So that it is not limited to shape memory alloys only, but all types of shape memory materials, even those conventional materials, such as many engineering polymers [13,15,16]; -The techniques to design/tailor the shape memory function of a material to meet the requirement(s) of a particular application [12]; -The techniques to optimize the shape memory performance [17].…”