Effect of the Addition of MgO Nanoparticles on the Thermally-Activated Shape Memory Behavior of Plasticized PLA Electrospun Fibers (original) (raw)
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Morphological and mechanical analysis of electrospun shape memory polymer fibers
Applied Surface Science, 2016
Shape memory block co-polymer Polyurethane (PU) fibers were fabricated by electrospinning technique. Four different solution concentrations (5 wt.%, 10 wt.%, 15 wt.% and 20 wt.%) were prepared by using Tetrahydrofuran (THF)/N,N-dimethylformamide (DMF) (50:50, v/v) as solvents, and three different voltages (30 kV, 35 kV and 38.9 kV) were determined for the electrospinning process. Solution properties were explored in terms of viscosity and electrical conductivity. It was observed that as the polymer concentration increased in the solution, the conductivity declined. Morphological characteristics of the obtained fibers were analyzed through Scanning Electron Microscopy (SEM) measurements. Findings indicated that fiber morphology varied especially with polymer concentration and applied voltage. Obtained fiber diameter ranged from 112 ± 34 nm to 2046 ± 654 nm, respectively. DSC analysis presented that chain orientation of the polymer increased after electrospinning process. Shape fixity and shape recovery calculations were realized. The best shape fixity value (92 ± 4%) was obtained for Y10K30 and the highest shape recovery measurement (130 ± 4%) was belonged to Y15K39. Mechanical properties of the electrospun webs were also investigated in both machine and transverse directions. Tensile and elongation values were also affected from fiber diameter distribution and morphological characteristics of the electrospun webs.
European Polymer Journal, 2017
A mat of fibers with shape memory effect is obtained using commercially available components and a simple electrospinning process. For obtaining this goal, a blend of diglycidyl ether of bisphenol A (DGEBA) and Polycaprolactone (PCL) is electrospun and the obtained mats are cured by UV radiation, avoiding the melting of the PCL component. The cationic photoinitiator based on iodonium salts, used for the first time in the electrospinning process, increases the solution conductivity and consequently the spinnability of the blend. The obtained mats show shape memory properties through several cycles, with shape fixity ratios that range from 95 to 99% and shape recovery ratios of between 88 and 100% respectively.
Polymers for Advanced Technologies, 2020
Herein, the electrospinning method, as an effective approach, was utilized to fabricate poly (ε‐caprolactone)‐based polyurethane (PCL‐based PU) fibers. PCL was synthesized by ring‐opening polymerization, and characterized by proton nuclear magnetic resonance (1H NMR) and Fourier‐transform infrared (FTIR) spectroscopies. Afterward, PU was prepared by step‐growth polymerization. The effects of solution concentration and solvent type on fibers' diameter were investigated. Scanning electron microscopy (SEM) images revealed that the optimum solution was N, N‐dimethylformamide(DMF): chloroform with a ratio of 60:40. In addition, results showed that bead‐less nanofibers could be achieved by a concentration of 5 w/v% (polymer to solvent). Various optimum practical parameters, such as applied voltage, feeding rate, and needle‐to‐collector distance, were obtained and compared with the results of response surface methodology (RSM). On the other hand, the mechanical evaluations indicated th...
Drug Delivery and Translational Research
This study is a proof of concept performed to evaluate process parameters affecting shape memory effect of copolymer poly-l-lactide-co-poly-ε-caprolactone (PLA:PCL) 70:30 ratio based nanofibrous scaffolds. A design of experiment (DOE) statistical approach was used to define the interaction between independent material and process variables related to electrospun scaffold manufacturing, such as polymer solution concentration (w/v%), spinning time (min), and needle size (Gauge), and their influence on Rf% (ability of the scaffold to maintain the induced temporary shape) and Rr% (ability of the scaffold to recover its original shape) outputs. A mathematical model was obtained from DOE useful to predict scaffold Rf% and Rr% values. PLA-PCL 15% w/v, 22G needle, and 20-min spinning time were selected to confirm the data obtained from theoretical model. Subsequent morphological (SEM), chemical-physical (GPC and DSC), mechanical (uniaxial tensile tests), and biological (cell viability and a...
PLA Electrospun Fibers Reinforced with Organic and Inorganic Nanoparticles: A Comparative Study
2021
In this work, different poly (lactic acid) (PLA)-based nanocomposite electrospun fibers, reinforced with both organic and inorganic nanoparticles, were obtained. As organic fibers, cellulose nanocrystals, CNC, both neat and functionalized by “grafting from” reaction, chitosan and graphene were used; meanwhile, hydroxyapatite and silver nanoparticles were used as inorganic fibers. All of the nanoparticles were added at 1 wt% with respect to the PLA matrix in order to be able to compare their effect. The main aim of this work was to study the morphological, thermal and mechanical properties of the different systems, looking for differences between the effects of the addition of organic or inorganic nanoparticles. No differences were found in either the glass transition temperature or the melting temperature between the different electrospun systems. However, systems reinforced with both neat and functionalized CNC exhibited an enhanced degree of crystallinity of the electrospun fibers...
Tailoring Crystallinity of Electrospun Plla Fibres by Control of Electrospinning Parameters
Polymers, 2012
Poly(L-lactic acid) (PLLA) fibers were fabricated by electrospinning. The effects of various electrospinning process parameters on the thermal properties, especially the crystallinity of the electrospun fibers were investigated. Thermal analysis of the fibers revealed that they exhibited degree of crystallinity ranging from 23% to 46% while that for the as-received granules was approximately 37%, suggesting that the crystallinity of electrospun PLLA fibres can be controlled by optimizing the electrospinning process. This finding is very important because crystallinity affects polymer properties such as degradation, stiffness, yield stress, modulus and tensile strength, solubility, optical and electrical properties which will in turn affect the behavior of these materials when they are utilized in energy, environment, defense and security applications. The results presented in this paper show that the degree of crystallinity of the electrospun fibers decreased with increasing the polymer solution concentration. Furthermore, an optimum electrospinning voltage at which maximum degree of crystallinity can be obtained was observed. At voltages higher or lower than the optimum electrospinning voltage, the degree of crystallinity will decrease or increase, respectively. The effect of the needle tip to collector distance (NTCD) on the degree of crystallinity follows no predictable and consistent pattern.
Polymers
Fibrous shape memory scaffolds composed of thermoplastic polyurethane based on a mixture of polycaprolactone diols were fabricated. The effect of the fiber diameter and arrangement– random (rPU) or aligned (aPU), on crystallinity, mechanical properties, and shape memory was analyzed. The diameters of the fibers were controlled by changing the concentration of polyurethane (PU) solutions in the range of 5% to 16% and fibers alignment by utilization of different collectors. The chemical structure was confirmed by Fourier Transformed Infrared spectroscopy (FTIR), crystallinity was evaluated based on differential scanning calorimetry (DSC,) and mechanical properties were measured by the tensile test. Additionally, shape memory programming was performed using a dynamic mechanical analyzer (DMA), and shape recovery was evaluated in the air and in the water environment. DSC results showed that the electrospinning process did not change the crystallinity or melting temperature of synthesize...
Study of the thermal properties of shape memory polyurethane nanofibrous nonwoven
Journal of Materials Science, 2011
Thermal properties of polymer are very important to the understanding of morphology and shape memory effect of shape memory polymers (SMPs). In this article, the thermal properties of shape memory polyurethane nanofibrous nonwoven are investigated systematically from the morphology of nanofibers, crystalline structure, isothermal crystallization behavior, and thermaldependent strain recovery. The results indicate that the thermal properties of shape memory polyurethane nanofibrous nonwoven are influenced greatly by the electrospinning and the recrystalline condition. The crystal melting temperature (T m ) decreases as the crystallization temperature (T c ) decreases, while the relative degree of crystallinity (X c ) increases with the decrease of T c within the temperature range of 20 to -30°C. In particular, when the annealing temperature is higher than 150°C, the T m shifts to higher value and the X c decreases significantly with the increase of T c . Finally, temperature-dependent strain recovery curves show that the shape memory polyurethane nanofiber tends to have a lower recovery temperature as compared with the SMPU bulk film due to their ultrafine diameter.