scholarly journals Shape-Memory-Recovery Characteristics of Microcellular Foamed Thermoplastic Polyurethane

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 351
Author(s):  
Chang-Seok Yun ◽  
Joo Seong Sohn ◽  
Sung Woon Cha
Keyword(s):  
Shape Memory ◽  
Cell Density ◽  
Shape Recovery ◽  
Structural Changes ◽  
Thermoplastic Polyurethane ◽  
Testing Machine ◽  
Base Material ◽  
Memory Mechanism ◽  
Foaming Process ◽  
Dog Bone

We investigated the shape-recovery characteristics of thermoplastic polyurethane (TPU) with a microcellular foaming process (MCP). Additionally, we investigated the correlation between changes in the microstructure and the shape-recovery characteristics of the polymers. TPU was selected as the base material, and the shape-recovery characteristics were confirmed using a universal testing machine, by manufacturing dog-bone-type injection-molded specimens. TPUs are reticular polymers with both soft and hard segments. In this study, we investigated the shape-memory mechanism of foamed polymers by maximizing the shape-memory properties of these polymers through a physical foaming process. Toward this end, TPU specimens were prepared by varying the gas pressure, foaming temperature, and type of foaming gas in the batch MCP. The effects of internal structural changes were investigated. These experimental variables affected the microstructure and shape-recovery characteristics of the foamed polymer. The generated cell density changed, which affected the shape-recovery characteristics. In general, a higher cell density corresponded to a higher shape-recovery ratio.

Characterization of Creeping and Shape Memory Effect in Laser Sintered Thermoplastic Polyurethane

2016 ◽  
Vol 16 (4) ◽  
Author(s):  
Shangqin Yuan ◽  
Jiaming Bai ◽  
Chee Kai Chua ◽  
Kun Zhou ◽  
Jun Wei
Keyword(s):  
Shape Memory ◽  
Shape Recovery ◽  
Thermoplastic Polyurethane ◽  
Selective Laser Sintering ◽  
Thermal Transitions ◽  
Temperature Dependent ◽  
Shape Memory Effects ◽  
Viscoelastic Behaviors ◽  
High Flexibility

Thermoplastic polyurethane (TPU) powders were successfully processed in a selective laser sintering (SLS) system. The laser-sintered polyurethane products with viscoelastic behaviors exhibit high flexibility and elongation at break at room temperature. Moreover, the creeping and the thermoresponsive shape-memory effects (SME) were also characterized. The influences of the time-temperature relevant parameters on the shape-fixity and shape-recovery ratios were investigated quantitatively. The creeping and SME were time–temperature dependent phenomena, and the shape recovery mechanism is associated to the microsegments thermal transitions within the polymer matrix.

scholarly journals Shape Memory Polyurethane Biocomposites Based on Toughened Polycaprolactone Promoted by Nano-Chitosan

Nanomaterials ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 225 ◽  
Author(s):  
Arvind Gupta ◽  
Beom Soo Kim
Keyword(s):  
Shape Memory ◽  
Biomedical Applications ◽  
Shape Recovery ◽  
Permanent Deformation ◽  
Testing Machine ◽  
Microscopic Analysis ◽  
Original Form ◽  
Electron Microscopic ◽  
Unique Shape ◽  
Shape Memory Polyurethane

The distinctive ability to remember their original form after partial or complete deformation makes shape memory polymers remarkable materials for several engineering and biomedical applications. In the present work, the development of a polycaprolactone based toughened shape memory polyurethane biocomposite promoted by in situ incorporation of chitosan flakes has been demonstrated. The chitosan flakes were homogeneously present in the polymer matrix in the form of nanoflakes, as confirmed by the electron microscopic analysis and probably developed a crosslinked node that promoted toughness (a > 500% elongation at break) and led to a ~130% increment in ultimate tensile strength, as analyzed using a universal testing machine. During a tensile pull, X-ray analysis revealed the development of crystallites, which resulted from a stress induced crystallization process that may retain the shape and melting of the crystallites stimulating shape recovery (with a ~100% shape recovery ratio), even after permanent deformation. The biodegradable polyurethane biocomposite also demonstrates relatively high thermal stability (Tmax at ~360 °C). The prepared material possesses a unique shape memory behavior, even after permanent deformation up to a > 500% strain, which may have great potential in several biomedical applications.

scholarly journals Hybrid Nanocomposites of Cellulose/Carbon-Nanotubes/Polyurethane with Rapidly Water Sensitive Shape Memory Effect and Strain Sensing Performance

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1586 ◽  
Author(s):  
Wu ◽  
Gu ◽  
Hou ◽  
Li ◽  
Ke ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Shape Memory ◽  
Shape Recovery ◽  
Thermoplastic Polyurethane ◽  
Cellulose Nanofibers ◽  
Hybrid Nanocomposites ◽  
Large Strains ◽  
Strain Sensing ◽  
Shape Memory Effects ◽  
Sensing Performance

In this work, a fast water-responsive shape memory hybrid polymer based on thermoplastic polyurethane (TPU) was prepared by crosslinking with hydroxyethyl cotton cellulose nanofibers (CNF-C) and multi-walled carbon nanotubes (CNTs). The effect of CNTs content on the electrical conductivity of TPU/CNF-C/CNTs nanocomposite was investigated for the feasibility of being a strain sensor. In order to know its durability, the mechanical and water-responsive shape memory effects were studied comprehensively. The results indicated good mechanical properties and sensing performance for the TPU matrix fully crosslinked with CNF-C and CNTs. The water-induced shape fixity ratio (Rf) and shape recovery ratio (Rr) were 49.65% and 76.64%, respectively, indicating that the deformed composite was able to recover its original shape under a stimulus. The TPU/CNF-C/CNTs samples under their fixed and recovered shapes were tested to investigate their sensing properties, such as periodicity, frequency, and repeatability of the sensor spline under different loadings. Results indicated that the hybrid composite can sense large strains accurately for more than 103 times and water-induced shape recovery can to some extent maintain the sensing accuracy after material fatigue. With such good properties, we envisage that this kind of composite may play a significant role in developing new generations of water-responsive sensors or actuators.

scholarly journals Mechanical Behaviour and Phase Transition Mechanisms of a Shape Memory Alloy by Means of a Novel Analytical Model

2018 ◽  
Vol 12 (2) ◽  
pp. 105-108 ◽  
Author(s):  
Andrea Carpinteri ◽  
Vittorio Di Cocco ◽  
Giovanni Fortese ◽  
Francesco Iacoviello ◽  
Stefano Natali ◽  
...  
Keyword(s):  
Phase Transition ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Analytical Model ◽  
Testing Machine ◽  
Martensite Phase ◽  
Niti Shape Memory Alloy ◽  
Stress Strain ◽  
Dog Bone ◽  
Strain Relationship

Abstract The aim of the present paper is to examine both the fatigue behaviour and the phase transition mechanisms of an equiatomic pseudo-elastic NiTi Shape Memory Alloy through cyclic tests (up to 100 loading cycles). More precisely, miniaturised dog-bone specimens are tested by using a customised testing machine and the contents of both austenite and martensite phase are experimentally measured by means of X-Ray diffraction (XRD) analyses. On the basis of such experimental results in terms of martensite content, an analytical model is here formulated to correlate the stress-strain relationship to the phase transition mechanisms. Finally, a validation of the present model by means of experimental data pertaining the stress-strain relationship is performed.

Tunable shape recovery progress of thermoplastic polyurethane by solvents

2018 ◽  
Vol 47 (1) ◽  
pp. 7-13 ◽  
Author(s):  
Changchun Wang ◽  
Bo Kou ◽  
Zusheng Hang ◽  
Xuejuan Zhao ◽  
Tianxuan Lu ◽  
...  
Keyword(s):  
Shape Memory ◽  
Internal Stress ◽  
Recovery Time ◽  
Shape Recovery ◽  
Thermoplastic Polyurethane ◽  
Recovery Process ◽  
Solubility Parameters ◽  
Content Type ◽  
Shape Memory Properties ◽  
Residual Strains

Purpose This study aims to present that the chemo-responsive shape recovery of thermoplastic polyurethane (TPU) is tunable by solvents with different solubility parameters, and it is generic for chemo-responsive shape-memory polymer and its composites. Design/methodology/approach Two kinds of commercial TPU samples with different thicknesses were prepared by panel vulcanizer and injection molding (an industrial manner) to investigate their chemo-responsive shape memory properties in acetic ether and acetone. Findings Results showed that all of TPU films with different thicknesses can fully recover their original shapes weather they recover in acetic ether or acetone. But the recovery time of TPU films in acetone is greatly reduced, especially for the twisting samples. The residual strains of recovery TPU samples after extension reduce obviously. Research limitations/implications The great decrement of recovery time is related to two factors. One is due to the bigger solubility parameter of acetone with higher dipole moment compared with those of acetic ether, and the other is the remained internal stress of TPU films after preparation. The internal stress is identified to have an effect on the shape-memory properties by comparing the recovery process of samples with/without annealing. The reduced residual strains of recovery TPU samples after extension is due to the increasing mobility of polymer segments after molecules of acetic ether penetrates into the polymeric chains. Originality/value This is a universal strategy to control the recovery process of shape-memory materials or composites. The underlying mechanism is generic and should be applicable to chemo-responsive shape-memory polymers or their composites.

Durability Assessment of Fabric-Reinforced Shape-Memory Polymer Composites

2009 ◽  
Author(s):  
G. P. Tandon ◽  
K. Goecke ◽  
K. Cable ◽  
J. Baur
Keyword(s):  
Shape Memory ◽  
Shape Recovery ◽  
Shape Memory Polymer ◽  
Current State ◽  
Dog Bone ◽  
Measured Weight ◽  
Before And After ◽  
Durability Assessment ◽  
Environmental Durability ◽  
Shape Fixity

The present study is a baseline assessment of the environmental durability of current state-of-the-art, fabric-reinforced shape memory materials being considered for morphing applications. Tensile dog-bone-shaped specimens are cut along three different directions, namely, along 0°, perpendicular (90°), and at 45° to the orientation of the fabric. The shape memory properties and elastomeric response before and after relevant environmental exposure to water at 49°C for 4 days, in lube oil at room temperature and at 49°C for 24 hours, and after exposure to Xenon Arc (63°C, 18 minutes water and light/102 minutes light only) and spectral intensity of 0.3 to 0.4 watts/m2 for 125 cycles (250 hours exposure time) are measured. Weight loss of the as-received and conditioned specimens is monitored while the dog-bone-shaped specimens are subjected to recovery following fixation. Parameters being investigated include stored strain, recovery stress, shape fixity, shape recovery, and modulus in the glassy and rubbery state.

Study of Biobased Shape Memory Polylactic Acid/Thermoplastic Polyurethane (PLA/TPU) Blends

2013 ◽  
Author(s):  
Xin Jing ◽  
Hao-Yang Mi ◽  
Lih-Sheng Turng ◽  
Xiang-Fang Peng
Keyword(s):  
Shape Memory ◽  
Polylactic Acid ◽  
Shape Recovery ◽  
Thermoplastic Polyurethane ◽  
Weight Ratio ◽  
Mechanical Tests ◽  
Dynamic Mechanical Analyzer ◽  
Scanning Calorimetry ◽  
Injection Molded ◽  
Flexural Tests

This paper presents the development of shape-memory polymers (SMPs) based on polylactic acid (PLA) and thermoplastic polyurethane (TPU) blends. PLA was melt blended with TPU at weight ratios of 20, 30, and 40%, and then injection molded and hot compressed into permanent shapes. Unlike most of the existing SMPs, all three PLA/TPU blends could be formed (via bending, folding, compression, stretching, etc.) into temporary shapes at room temperature without an extra heating step. Upon heating to above the glass transition temperature of PLA (at 70 °C), the deformed parts regained their original shapes quickly. Differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) tests showed that PLA and TPU were immiscible. The dynamic mechanical analyzer (DMA) data and the mechanical tests, including tensile, compression, and flexural tests, showed that the PLA/TPU with the 80/20 weight ratio had the best shape-memory properties, even if it was somewhat brittle. The 70/30 PLA/TPU blend had the best combination of shape recovery and mechanical properties.

Understanding the shape memory behavior of thermoplastic polyurethane elastomers with coarse-grained molecular dynamics simulations

MRS Advances ◽  
2017 ◽  
Vol 2 (6) ◽  
pp. 375-380 ◽  
Author(s):  
Md Salah Uddin ◽  
Jaehyung Ju
Keyword(s):  
Molecular Dynamics ◽  
Shape Memory ◽  
Shape Recovery ◽  
Thermoplastic Polyurethane ◽  
Coarse Grained ◽  
Polyurethane Elastomers ◽  
Weight Percentage ◽  
Shape Memory Behavior ◽  
Soft Segments ◽  
Hard Segments

ABSTRACTWe perform molecular dynamics (MD) simulations to understand thermally triggered shape memory behavior of a thermoplastic polyurethane (TPU) elastomer with an enhanced coarse-grained (CG) model. Hard and soft phases of shape memory polymers (SMPs) are known as fixed and reversible phase, respectively. Fixity depends on the content of hard segments due to their restricted mobility. On the contrary, recovery depends on the dynamic motion of the soft segments as well the degree of cross-linking, which is also affected by the quantity of hard segment. Several CG models of the TPU are constructed varying the weight percentage of soft segments to observe their effects on shape recovery and fixity. All of the models are equilibrated at 300K (above glass transition, Tg: 200-250 K) and deformed under uniaxial loading with NPT (isothermal-isobaric) ensembles. The deformed state is cooled to 100K (below Tg) and further equilibrated to estimate the shape fixity. Shape recovery is predicted by heating and equilibrating the structures back to 300K. By the end of this study, we may answer how much the shape fixities and recoveries are changed for varying concentration of hard segments from thermomechanical cycles with CGMD simulations.

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