An investigation on shape memory behaviors of epoxy resin system
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memory epoxy is receiving considerable attention because of its superior mechanical and thermal properties and excellent shape-memory performance. In this study, a novel series of shape-memory epoxy resins are prepared using hydro-epoxy, hexahydrophthalic anhydride, and diglycidyl 4,5-epoxy tetrahydro phthalate (TDE-85) to further improve the recovery force of shape-memory epoxy resins. The thermal, mechanical, and shape-memory properties of the shape-memory epoxy resin system are investigated by differential scanning calorimetry, dynamic mechanical analysis, bend test, and shape recovery test. Results indicate that the glass transition temperature (Tg), rubber modulus, and room-temperature bend strength increase as TDE-85 content increases. Investigation of the shape-memory behavior of the resin reveals that full recovery can be achieved after only several minutes when the temperature is equal to or above Tg. The shape recovery time decreases with the increase in TDE-85 content at Tg, Tg 1 10 °C, and Tg 1 20 °C. These results are attributed to the increase in TDE-85 content.
I. INTRODUCTION
Shape-memory polymers (SMPs) are a class of smart polymeric materials that can recover the original shape from a temporary shape by external stimuli on demand. Thermal-sensitive SMPs that use temperature change as their external stimulus are the most common SMPs.1–9 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. In the past 50 years, SMPs have attracted considerable attention because of its unique properties.10–12 Common SMP chemical components include polynorbornene,13 polycaprolactone,14 polyurethane,15–18 styrene copolymer,19,20 and epoxy.21,22 Among these SMPs, shape-memory epoxy resins have higher modulus and greater thermal and chemical stabilities than the others. They are commonly used as matrix materials in structural composites, which drastically improve the stiffness and shape recovery force of SMPs. Liu et al.23 investigated the shape-memory properties of epoxy-based. SMPs with different curing degrees. They found that epoxy-based SMPs with different curing degrees have excellent shape-memory performances and a wide range of well-separated transition temperatures. Xie and Contributing Editor: Tao Xie Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2015.180 J. Mater. Res., Vol. 30, No. 14, Jul 28, 2015
Rousseau 24 found that varying the cross-link density by substituting the diamine curing agent with a monoamine could tune the glass transition temperature (Tg ) of epoxy-based SMPs. Liu et al.25 filled shape-memory epoxy with 20 wt% SiC nanopowder, and found that the recovery force of the SMP nanocomposite was also higher than that of pure SMP. Although shape-memory epoxies have several advantages than the other SMPs, the recovery force of shape-memory epoxy is relatively low, which limit their application.26,
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