Thermomechanical characterization of thermoset urethane shape‐memory polymer foams

Abstract

The shape-memory polymer performance of urethane foams compressed under a variety of conditions was characterized. The foams were water-blown thermosets with a closed-cell structure and ranged in density from about 0.25 to 0.75 g/cm 3 . Compressive deformations were carried out over a range of strain levels, temperatures, and lateral constraints. Recovery stresses measured between fixed platens were as high as 4 MPa. Recovery strains, measured against loads up to 0.13 MPa, demonstrated the effects of various parameters. The results suggest that compression near the foam glass-transition temperature provided optimal performance. Foams with densities of about 0.5 g/cc and compressed 50% provided a useful balance (time, strain, and load) in the recovery performance.

Porous Shape-Memory Polymers

“…Similar trends of compressive stresses, recovery dynamics and percent recovery for higher foam density and lower temperature of compression were reported by Domeier et al [62] In general, compression close to T g onset appeared to provide optimal recovery performance in terms of high recovery stresses and low hysteresis. [62] …”

“…[35, 58-60] Chung and Park fabricated polyurethane SMP foams from a segmented thermoplastic polyurethane using salt leaching, [27] and Chung, Kang, and co-workers also fabricated an electrospun web using the same thermoplastic polyurethane. [61] Domeier [62] and Lee [19] also studied polyurethane based SMP foams (Table 1). …”

“…Domeier studied high density “tough” urethane SMPs with porosities from 25 to 75% and closed cell structure. [62] …”

Review on the Functional Determinants and Durability of Shape Memory Polymers

“…In this way, the environment, which is used to evaluate SM properties, is equalized with the utilized thermo-mechanical characterization method. Applications for SMPs are diverse and involve deformations like bending, compression and drawing, accordingly there are different testing methods to quantify the SM behavior of a polymer, such as bending tests [174][175][176], fold-deploy tests [135], uniaxial experiments (unconstrained free strain recovery tests, stress recovery tests under full constraint at a fixed strain level [101,177], isothermal uniaxial compression tests [178] and other tests developed for SMP foams [179][180][181][182][183]) and isothermal free strain recovery tests in warm water baths, during which a video camera collects images at a well-defined rate, e.g., at 20 frames-per-second ( Figure 1) [184,185]. In some cases, a dynamic mechanical analyzer has been used to evaluate SM properties [88].…”

An investigation on shape memory behaviors of epoxy resin system

“…Thermal-sensitive SMPs that use temperature change as their external stimulus are the most common SMPs. [1][2][3][4][5][6][7][8][9] Since the 1960s, covalently cross-linked polyethylene has found broad applications as heat-shrinking films or tubings. The importance of SMPs is gradually being taken seriously to date.…”