Effect of physical aging on the shape-memory behavior of amorphous networks

• Published in: Polymer (Guilford) Vol. 53; no. 12; pp. 2453 - 2464
• Main Authors: Choi, Jinwoo, Ortega, Alicia M., Xiao, Rui, Yakacki, Christopher M., Nguyen, Thao D.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 25.05.2012; Elsevier
• Subjects: Activation; Activation analysis; Applied sciences; crosslinking; ethylene glycol; Exact sciences and technology; Glycol dimethacrylates; Mathematical models; Mechanical properties; Networks; Optimization; Organic polymers; Physical aging; Physicochemistry of polymers; polymers; Properties and characterization; Recovery; Shape memory; Shape-memory polymers; temperature; Viscoelasticity; Viscoelasticity; Shape-memory polymers; Physical aging; Crosslinked copolymer; Shape memory effect; Long term variation; Methacrylate copolymer; Ethylene oxide copolymer; Experimental study; Modeling; Structure relaxation; Amorphous copolymer
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2012.03.066

This paper presents an experimental and modeling study of the effects of physical aging on the shape-memory performance of (meth)acrylate-based networks composed of tert-butyl acrylate (tBA) crosslinked by various concentrations of poly(ethylene glycol dimethacrylate) (PEGDMA). The experiments measured the unconstrained recovery response of samples stored at 20 °C (Tg − 36 °C) for zero to 180 days and evaluated the effects of storage on the strain fixity, activation temperature, and initial recovery rate. A thermoviscoelastic model recently developed for amorphous networks near the Tg was applied to study the influence of structural and viscoelastic relaxation and the aging time and temperature on the recovery response. Results showed that the activation temperature and the initial recovery rate increased with the aging time, producing a sharper initial recovery response. The thermoviscoelastic model predicted that the magnitude of these effects depended on the aging temperature. There was an optimum aging temperature that maximized the initial recovery rate. These results suggest that physical aging can be manipulated to accelerate the recovery performance of shape-memory polymer devices. [Display omitted]