Elastic Shape Memory Hybrids Programmable at Around Body-Temperature for Comfort Fitting

Abstract

A series of silicone based elastic shape memory hybrids are fabricated. Their shape memory performance, mechanical behaviors at room temperature with/without programming and during fitting at 37 °C are investigated. It is found that these materials have good shape memory effect and are always highly elastic. At 37 °C, there are 10 min or more for fitting. Thus, it is concluded that this type of material has great potential as an elastic shape memory material for comfort fitting.

Keywords: comfort fitting; elasticity; hardening time; shape memory effect; shape memory hybrid.

Figure 1

Dimensions of the sample (unit: mm). The thickness of the sample is 6 mm. Five different types of samples/hybrids—named SPPMx (x = 1 to 5)—were produced. Refer to Table 1 for their actual compositions.

Figure 2

DSC results of PPM002040 at heating/cooling speeds of 10 °C/min (black line) and 5 °C/min (grey line).

Figure 3

Typical scanning electron microscope (SEM) image of SPPM4. The scale bar is 50 µm.

Figure 4

Typical stress vs. strain relationships of SPPM samples under uni-axial tension at room temperature to fracture.

Figure 5

Typical stress vs. strain relationships under uni-axial cyclic tension at room temperature of all samples (a) and zoom-in view of all samples excluding SPPM2 (b).

Figure 6

Typical stress vs. strain relationships of all samples programmed with 20% strain (a) and 50% strain (b).

Figure 7

Comparison of the stress vs. strain relationships under uni-axial tension at room temperature and 37 °C (to 20% and 50% strains) in SPPM1 (a), SPPM2 (b), SPPM3 (c), SPPM4 (d) and SPPM5 (e).

Figure 7

Comparison of the stress vs. strain relationships under uni-axial tension at room temperature and 37 °C (to 20% and 50% strains) in SPPM1 (a), SPPM2 (b), SPPM3 (c), SPPM4 (d) and SPPM5 (e).

Figure 8

Comparison of the corresponding stresses at 20% and 50% strains in loading at room temperature and in programming (at 37 °C).

Figure 9

SPPM samples after heated at 50 °C for five minutes. In each sample, the applied programming strain is indicated at right above the hybrid type (1 to 5). The right sample is original as marked without any testing for comparison.

Figure 10

Shape fixity ratio and shape recovery ratio of all SPPM samples (black hollow symbols: shape fixity ratio; grey solid symbols: shape recovery ratio). The applied programming strain in each sample is indicated in % in the legend (top).

Figure 11

Evolution in the stress vs. strain relationship of all SPPM samples under cyclic uni-axial tension during crystallization induced hardening at 37 °C (a); and the slope ratios in loading at 20% strain in the loading process of each cycle as a function of testing time (b) (in which the slope of the stress vs. strain curve at 20% strain of the first cycle of each sample is taken as the reference).

Figure 12

Typical stress vs. strain relationships under uni-axial cyclic tension at room temperature in all samples programmed with 20% strain (a) and zoom-in view for samples excluding SPPM2 (b); and programmed with 50% strain (c) and zoom-in view for samples excluding SPPM2 (d).