Structure and mechanical properties of shape memory polyurethane based on hyperbranched polyesters

• Published in: Polymer bulletin (Berlin, Germany) Germany), 2006-10, Vol.57 (6), p.889-899
• Main Authors: Cao, Qi, Liu, Pengsheng
• Format: Article
• Language: English
• Subjects: Applied sciences; Diphenyl methane diisocyanate; Dynamic mechanical analysis; Exact sciences and technology; Heat of crystallization; Mechanical properties; Organic polymers; Physical properties; Physicochemistry of polymers; Polyester resins; Polymers with particular properties; Polyurethane resins; Preparation, kinetics, thermodynamics, mechanism and catalysts; Segments; Shape memory; Transition temperature
• ISSN: 0170-0839; 1436-2449
• DOI: 10.1007/s00289-006-0650-z

SummaryHyperbranched shape memory polyurethane (HB-SMPU) were prepared from 4,4’-diphenylmethane diisocyanate, poly (butylenes adipate) glycol, and hyperbranched polyester as chain extender via a two-step process. The morphology of the HB-SMPU films was investigated by the use of wide-angle X-ray diffraction (WAXD), atomic force microscopy (AFM), DSC and dynamic mechanical analysis (DMA). It was found that the PBAG soft segments in HB-SMPU with 15–35 wt. % of hard segments were in a crystalline state, however, the PBAG segments were in an amorphous state in the HB-SMPU with 40 wt. % hard segments. The increase of the hard segment content resulted in the decrease of the melt transition temperature of the HB-SMPU. The HB-SMPU with 25 wt. % of hard segment content possessed highest loss tangent. Heat of crystallization was dependent on the content of hard segment in the HB-SMPU. 96–98 wt. % shape recovery could be obtained for the HB-SMPU with 15–35 wt. % of hard segment. The content of hard segments in HB-SMPU was very important in determining their physical properties.