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.

Relationship between Annealing and Shape Memory Effect of Shape Memory Polyurethane

2014 ◽  
Vol 936 ◽  
pp. 140-144 ◽  
Author(s):  
Jia Ying ◽  
Masaaki Nishikawa ◽  
Masaki Hojo
Keyword(s):  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Shape Recovery ◽  
Length Change ◽  
Recovery Ratio ◽  
High Entropy ◽  
Change Of State ◽  
Relationship Of ◽  
Shape Memory Polyurethane

The relationship of annealing and shape memory effect of uniaxially oriented shape memory polyurethane was studied; meanwhile a new method of adjusting shape recovery ratio by annealing was proposed for further consideration. Experiments were designed to compare the influence on length change from annealing and shape memory effect with shape memory polyurethane film at 65°C. We found that for shape memory polyurethane which had residual strain from material processing procedure, annealing and shape memory effect have the same effect on its length change if they are both carried out at the same temperature. It is because annealing and shape memory effect have the same mechanism, which is the change of state from low conformational entropy states to the recovery of a stable high entropy state in the polymer. Moreover, it is proved by experiment that shape recovery ratio of shape memory polyurethane can be adjusted by annealing.

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.

Study of a Cu-Al-Mn Shape Memory Alloy Produced by Plasma Melting Followed by Injection Molding

2014 ◽  
Vol 1611 ◽  
pp. 25-30
Author(s):  
Francisco Fernando Roberto Pereira ◽  
Maria Goretti Ferreira Coutinho ◽  
Bruno Moura Miranda ◽  
Carlos José de Araújo
Keyword(s):  
Injection Molding ◽  
Shape Memory ◽  
Shape Recovery ◽  
Permanent Deformation ◽  
Melting Process ◽  
Mechanical Analysis ◽  
Scanning Calorimetry ◽  
Dynamical Mechanical Analysis ◽  
Plasma Melting ◽  
New Applications

ABSTRACTShape Memory Alloys (SMA) are characterized by the capacity to recover a permanent deformation after being heated above a critical temperature called Final Austenite Temperature (Af). The Ni-Ti SMA are the most commercially used, however recent studies showed that the Cu-Al-Mn SMA present significant shape recovery and mechanical properties, showing a strong potential for developing new applications. In this context, the main goal of this work is to manufacture a Cu-Al-Mn SMA through a plasma melting process followed by injection molding of liquid metal and then characterize the samples, using the following techniques: Optical Microscopy (OM), Differential Scanning Calorimetry (DSC), Electrical Resistance as a function of Temperature (ERT) tests, Dynamical Mechanical Analysis (DMA) and Microhardness (MH).

Cellulose nanocrystals (CNC) reinforced shape memory polyurethane ribbons for future biomedical applications and design

2018 ◽  
Vol 33 (3) ◽  
pp. 377-392 ◽  
Author(s):  
Irina T Garces ◽  
Samira Aslanzadeh ◽  
Yaman Boluk ◽  
Cagri Ayranci
Keyword(s):  
Shape Memory ◽  
Cellulose Nanocrystals ◽  
Biomedical Applications ◽  
Flexural Modulus ◽  
Potential Candidate ◽  
The Past ◽  
Printing Cost ◽  
Surgical Sutures ◽  
Orthodontic Devices ◽  
Shape Memory Polyurethane

Shape memory materials are an innovative type of materials that reversibly store a temporary shape and recover back to the original dimensions with the application of an external mechanism such as heat. Shape memory polymers (SMP), specifically thermoplastic SMP (e.g. shape memory polyurethane (SMPU)) have received much attention during the past decade because of the promising future applications and advantages such as ease of processability for thermoplastic SMP (e.g. by 3-D printing), cost, and biocompatibility. In the biomedical field, applications such as stents, surgical sutures, and orthodontic devices, amongst others have been proposed. The addition of fillers to the material can modify the material to improve their load bearing capabilities. Bio-based fillers such as cellulose nanocrystals (CNC) have been proposed in a variety of reinforcing applications. The present work focuses on the experimental description of the addition of nonmodified CNC to SMPU. The work studied the effect on melt-extruded ribbons, for 0, 0.5, 1, 2, and 4 wt%. An increase of yield point, toughness, flexural modulus, recovery rate, and decrease of total time showed that SMPU/CNC nanocomposites are a potential candidate to use in future biomedical applications.

Optimizing the Thermomechanics of Shape-Memory Polymers for Biomedical Applications

2004 ◽  
Vol 855 ◽  
Author(s):  
Christopher M. Yakacki ◽  
Ken Gall ◽  
Robin Shandas ◽  
Alicia M. Ortega ◽  
Nick Willett ◽  
...  
Keyword(s):  
Shape Memory ◽  
Biomedical Applications ◽  
Shape Recovery ◽  
Polymer Networks ◽  
Shape Memory Polymers ◽  
Strain Recovery ◽  
Stress Recovery ◽  
High Deformation ◽  
Flexural Tests ◽  
Free Strain

ABSTRACTWe examine the shape-memory effect in polymer networks intended for biomedical applications. The polymers were photopolymerized from tert-butyl acrylate (tBA) with polyethyleneglycol dimethacrylate (PEGDMA) acting as a crosslinker. Three-point flexural tests were used to systematically investigate the thermomechanics of shape-storage deformation and shape recovery. The glass transition temperature (Tg) of the polymers varied over a range of 100°C and is dependent on the molecular weight and concentration of the crosslinker. The polymers show 100% strain recovery up to maximum strains of approximately 80% at low and high deformation temperatures (Td). Free strain recovery was determined to depend on the temperature during deformation; lower deformation temperatures (Td < Tg) decreased the temperature required for free strain recovery. Constrained stress recovery shows a complex evolution as a function of temperature and also depends on Td. The thermomechanical results are discussed in light of potential biomedical applications and a prototype stent that can be activated at body temperature is presented.

Grafting of shape memory polyurethane with poly(ethyleneimine) and the effect on electrolytic attraction in aqueous solution and shape recovery properties

2011 ◽  
Vol 20 (1) ◽  
pp. 66-75 ◽  
Author(s):  
Yong-Chan Chung ◽  
Jong Shin Park ◽  
Chang Hoon Shin ◽  
Jae Won Choi ◽  
Byoung Chul Chun
Keyword(s):  
Aqueous Solution ◽  
Shape Memory ◽  
Shape Recovery ◽  
Shape Memory Polyurethane

Castor oil and PEG-based shape memory polyurethane films for biomedical applications

2014 ◽  
Vol 131 (15) ◽  
pp. n/a-n/a ◽  
Author(s):  
Mirey Bonfil ◽  
Ahmet Sirkecioglu ◽  
Ozlem Bingol-Ozakpinar ◽  
Fikriye Uras ◽  
F. Seniha Güner
Keyword(s):  
Shape Memory ◽  
Castor Oil ◽  
Biomedical Applications ◽  
Shape Memory Polyurethane
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