Shape memory polyurethanes thermal-mechanical properties

Yang, J. H., Chun, B. C., Chung, Y.-C., Cho, J. H. (2003), Comparison of thermal/ mechanical properties and shape memory effect of polyurethane block-copolymers with planar or bent shape of hard segment. Polymer, 44, 3251-8. 

Abstract This chapter introduces three sets of T -type shape memory polyurethanes. The thermal properties and morphological structure of polymers are shown to vary with chemical composition. The morphology of the T -SMPUs is thus correlated to shape memory properties. The influences of several important thermo-mechanical conditions including deformation temperature, deformation strain, and shape fixing temperature and time on shape memory properties are demonstrated. 

Abstract This chapter presents the thermaUy-indnced shape memory properties of supramolecular shape memory polyurethane (SMPU) containing pyriine moieties, and compares them with those of other types of SMPU. llie influence of the BINA content and the MDI-BDO content on the thermally-induced shape memory effects (SMEs) of these SMPUs are discussed, including shape fixity, shape recovery and shape recovery stress, as well as the temperature-dependent strain recovery process. A description and analysis of the mechanism of thermaUy-induced SMEs is also provided, covering the effect of temperature and pyridine content on the hydrogen bonds present in SMPUs. 

Abstract This chapter introduces the moisture-induced shape memory effect (SME) observed in supramolecular shape memory polymers, particularly shape memory polyurethane (SMPU), containing pyridine moieties. The moisture absorption of polyurethane networks containing pyridine moeties (PUPy) is discussed followed by an investigation into the effect of relative humidity (RH), temperature, BINA content and MDI-BDO content. The induence of moisture absorption on both the thermal properties and the dynamic mechanical properties of SMPUs is also described, along with the moisture-induced SME mechanism. 

A. M. (2013) Thermal, mechanical and electroactive shape memory properties of polyurethane (PU)/poly(lactic acid)(PLA)/CNT nanocomposites. Eur. Polyrtu /., 49 (11), 3492-3500. 

Sahoo, N.G., et al. Influence of carbon nanotubes and polypyrrole on the thermal, mechanical and electroactive shape-memory properties of polyurethane nanocomposites.Co/zzpo5.5cz. Technol. 2007, 67(9), 1920-1929. 

NCC can be successfully applied as a reinforcement in nanocomposites ensuring improved barrier and mechanical properties. There are also less obvious applications for NCC such as aerogels and adhesive materials. In 2012, Auad et al. proved that the addition of NCC improves thermal performances of shape memory segmented polyurethanes [24,26]. 

In this section, mixed-phase polyurethanes prepared from 1,3-butane diol (1,3-BD), HDI, and MDI are reviewed [28]. When the TPU soft and hard segments are phase-mixed, a second element acting as a fixed phase should be introduced. This second element is typically crosslinks intoduced either by an allophanate reaction or by a multifunctional polyol. Shape memory properties, melt viscosities, dynamic mechanical and thermal properties, and stress relaxations in the glassy and rubbery states are discussed. 

Thermoplastic polyurethane-carbon nanofiber, TPU-CNF, conposites were prepared in situ in a chaotic mixer. Two types of CNF with different levels of surface oxidation were mixed with a shape memory TPU. Electrical condnctivity, thermal behavior, and mechanical properties were investigated. Electrical and thermal-induced shape recovery behaviors were evaluated. TPU with treated CNF showed better dispersion, crystallinity, tensile properties, and better shape memory properties snch as higher shape recovery force than their counterparts with rmtreated CNF. 

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