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Shape-memory Properties (shape-memory + property)
Selected AbstractsShape-memory polymer networks from oligo(,-caprolactone)dimethacrylatesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 7 2005Andreas Lendlein Abstract Polymer networks showing a thermally induced shape-memory effect were prepared through the crosslinking of oligo(,-caprolactone)dimethacrylates under photocuring with or without an initiator. The influence of the molecular weight of the oligo(,-caprolactone)dimethacrylates and the initiator concentration on the macroscopic properties of the polymer networks was investigated. The isothermal and nonisothermal crystallization behavior of the polymer networks was evaluated as a basic principle of the functionalization process. Shape-memory properties such as the strain fixity and strain recovery rate were quantified with cyclic thermomechanical tensile experiments for different maximum elongations. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1369,1381, 2005 [source] Novel Shape-Memory Materials Based on Potato StarchMACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2010Cyril Véchambre Abstract Shape-memory properties such as shape fixity and recovery ratio of amorphous starch-based materials extruded under normal conditions were evaluated for the case of single and cyclic recovery processing. This study focused on the effect of moisture as a stimulus for the activation of recovery. A high recovery ratio (Rr,>,90%) was obtained at high relative humidity, at deformation ratios up to 200%. In the case of plasticized starch with a glycerol content of 10%, the recovery ratio was close to 50% because crystallization limited the shape recovery. Results were compared to those obtained with synthetic or bio-based shape-memory polymers such as semi-crystalline PU or PLAGC. Efficient shape memory properties for a non-modified biopolymer are highlighted in this study. [source] Cast NiTi Shape-Memory Alloys,ADVANCED ENGINEERING MATERIALS, Issue 6 2005M. Ortega The purpose of this study is to build a fundamental understanding of the relationship between the structure and properties of cast nickel-titanium (NiTi). The structure of the cast material will be analyzed at various scales and will be related to the properties of the cast material such as transformation temperatures, stress-strain behavior, and recovery properties. This study demonstrates that cast NiTi can possess excellent shape-memory properties. [source] Novel interpenetrating networks with shape-memory propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2007Shifeng Zhang Abstract Novel polyesterurethane/poly(ethylene glycol) dimethacrylate (PEGDMA) interpenetrating networks (IPNs) with good shape-memory properties were synthesized using solvent casting method. The star-shaped oligo[(rac -lactide)- co -glycolide] was coupled with isophorone diisocyanate to form a polyesterurethane network (PULG), and PEGDMA was photopolymerized to form another polyetheracrylate network. IPNs were transparent and gel content exceeded 92%. The values of strain fixity rate and strain recovery rate were above 93%. PULG and PEGDMA networks in IPNs were amorphous and did not show any characteristic diffraction peaks in X-ray diffraction spectra. Only one glass transition temperature (Tg) of the IPNs between Tg of PEGDMA and PULG was observed, which was proportional to PEGDMA content. PULG and PEGDMA networks were miscible when PEGDMA content was below 50 wt %. The hydrophilicity, transition temperatures, and mechanical properties of IPNs could be conveniently adjusted through variation of network compositions to match the promising potential clinical or medical applications. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 768,775, 2007 [source] Photocurable Shape-Memory Copolymers of , -Caprolactone and L -LactideMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2010Minoru Nagata Abstract Biodegradable and photocurable block copolymers of , -caprolactone and L -lactide were synthesized by polycondensation of PLLA diol (,=,10,000,g,·,mol,1), PCL diol (,=,10,000,g,·,mol,1), and a chain extender bearing a coumarin group. The effect of copolymer composition on the thermal and mechanical properties of the photocured copolymers was studied by means of DSC and cyclic tensile tests. An increase in Young's modulus and a decrease in the tensile strain with increasing PLLA content was observed for the block copolymers. Block copolymers with high PCL content showed good to excellent shape-memory properties. Random copolymers exhibited Rf and Rr values above 90% at 45,°C for an extremely large tensile strain of 1,000%. [source] Composites of carbon nanofibers and thermoplastic polyurethanes with shape-memory properties prepared by chaotic mixingPOLYMER ENGINEERING & SCIENCE, Issue 10 2009Guillermo A. Jimenez Composites of carbon nanofibers (CNFs), oxidized carbon nanofibers (ox-CNFs), and shape-memory thermoplastic polyurethane (TPU) were prepared in a chaotic mixer and their shape-memory properties evaluated. The polymer was synthesized from 4,4,-diphenylmethane diisocyanate, 1,4-butanediol chain extender, and semicrystalline poly(,-caprolactone) diol soft segments. The shape-memory action was triggered by both conductive and resistive heating. It was found that soft segment crystallinity and mechanical reinforcement by nanofibers produced competing effects on shape-memory properties. A large reduction in soft segment crystallinity in the presence of CNF and stronger mechanical reinforcement by well-dispersed ox-CNF determined the shape-memory properties of the respective composites. It was found that the maximum shape recovery force, respectively, 3 and 4 MPa, was obtained in the cases of 5 and 1 wt% CNF and ox-CNF, respectively, compared with ,1.8 MPa for unfilled TPU. The degree of soft segment and hard segment phase separation and thermal stability of the composites were analyzed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers. [source] | ||||||||||