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Design of orthogonal Table L 9 (3) 4 and the ultimate tensile strength (UTS) of hot-pressed aligned electrospun fibers.
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Nanofibers and composite nanofibers have been used as mechanical reinforcement in a bulk matrix, but there is little research done on bulk nanocomposites made out of nanofibers. In the current study, in situ grown composite fibers of poly(DL-lactide) (PDLLA) and hydroxyapatite (HA) were obtained with uniaxial distribution, which were deposited by l...
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... hot-press temperature was set at 60, 100, and 140 8C, the hot-press pressure was 1, 2, and 3 MPa, and the holding time was 5, 10, and 15 min, respectively. Table 1 shows the orthogonal Table L 9 (3) 4 , in which a blank column was designated for the error evaluation. Aligned fibers A-EF were deposited into strips of 5 Â 10 cm 2 before hot-pressing, and the mechanical properties were determined as above. ...
Context 2
... experimental design is one way to qualitatively analyze effects of the process parameters on the resulting properties through designing orthogonal table and statistic analysis. [19] Table 1 summarizes the statistics analysis of the effect of different factors on the ultimate tensile strength of hot-pressed composites. The range analysis was aimed to clarify the significance levels of different process factors. ...
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... Based on analysis of pore size (Fig. 2c), aligned fibers exhibited porous, beadless, uni- form morphology with interconnected pores smaller than those in randomly oriented nanofibers. This is probably due to the increased separation of aligned fibers during fabrication as a result of repul- sion between residual surface charges [20]. Alignment in PLA/chitosan mats was also measured, since this is a key architectural feature for cardiac cells [21]. ...
Fibrous scaffolds with different ratios of poly (lactic acid) (PLA) and chitosan were fabricated by conventional electrospinning. After crosslinking by the glutaraldehyde vapor, the structure, mechanical properties, hydrophilicity, and in-fiber chemical interactions of the scaffolds were investigated. We found that the fiber diameter decreased with the concentration of chitosan, while mechanical properties and hydrophilicity improved. In addition, we found that scaffolds with aligned fibers have higher mechanical strength and biocompatibility than scaffolds with randomly oriented fibers. In particular, scaffolds with aligned fibers with PLA:chitosan ratios of 7:1 was found to support cardiomyocyte viability, elicit cell elongation, and enhance production of sarcomeric α-actinin and troponin I. Collectively, the data indicate that composite scaffolds consisting of PLA/chitosan fibers have great potential for engineering cardiac tissue, and for accelerating the regeneration of myocardia.
... The resultant polymer nanofibers assembled by electrospinning are featured on large specific surface area, and it can enable the applied load to be transferred on nanofibersmatrix interface [6][7][8][9][10]. Some researchers have attempted to manufacture nanocomposites reinforced with electrospun polymer nanofibers [11][12][13][14][15][16][17][18]. Among them, Uyar et al. [12] have used electrospun polyvinyl alcohol (PVA) to reinforce the polymethylmethacrylate (PMMA) composites resins, and their results indicated that the mechanical properties of PMMA composites were improved, and the improvement was higher when aligned PVA nanofibers are used. ...
Well-aligned PMIA nanofiber mats were fabricated by electrospinning and then hot-pressing was used to produce PMIA nanofiber mats reinforced PLA matrix by layer-by-layer with the interlayer angles of 0, 45, and 90°. Orthogonal experimental design was employed to fix the effect of the hot-pressing parameters on the tensile strength of nanocomposites, and SEM was used to characterize the broken sections of the nanocomposites after tensile test. The optimized process parameters were achieved of pressure as 1000 Pa, temperature as 180°C, and time as 30 min. The SEM images of broken sections showed that the different laminate forms and the state of bearing load of nanofibers resulted in the different morphologies of broken sections. The break strength of PMIA/PLA nanocomposites with any of interlayer angles at different tensile testing directions was revealed as follows: axial > oblique > transverse, and the initial modulus also showed the same except the angle of 90° with the approach initial modulus at the axial and transverse directions. The maximum tensile strength and modulus of the nanocomposites were 17.12 MPa and 1642.17 MPa, respectively, of the axial tensile testing directions of the interlayer angle of 0°.
... A high voltage differ- ence of 20 kV/15 cm was applied between the syringe nozzle and a grounded collector through a high voltage statitron (Tianjing High Volt- age Power Supply Co., Tianjing, China). Fibers were deposited on an alu- minum foil wrapped on a grounded rotating mandrel at a linear rate of around 15m/s [18]. The collected fibers were vacuum dried to remove solvent residue. ...
... Scanning electron microscopy (SEM, FEI Quanta 200, The Nether- lands) was used to visualize the structural topography of fibrous mats, which were sputter-coated with a thin layer of gold to minimize the charging effect. The fiber diameter and alignment were measured from SEM images with a magnification of 3000 as described previously [18]. At least 50 different sites from each SEM image were randomly chosen and measured to generate an average value. ...
... Fig. 1a and b show typical SEM morphologies of PELA/CNT fibrous mats, indicating a high alignment. The fibers were collected on a rotating mandrel, which provided additional drawing on fibers during the electrospinning process [18]. Blend and coaxial electrospinning were used to control the distribution of CNTs within fibers. ...
The key to addressing the challenges facing cardiac tissue engineering is the integration of physical, chemical, and electrical cues into scaffolds. Aligned and conductive scaffolds have been fabricated as synthetic microenvironments to improve the function of cardiomyocytes. However, up to now, the influence of conductive capability and inner structure of fibrous scaffolds have not been determined on the cardiomyocyte morphologies and beating patterns. In the current study, highly aligned fibers were fabricated with loaded up to 6% of carbon nanotubes (CNTs) to modulate the electrical conductivity, while blend and coaxial electrospinning were utilized to create a bulk distribution of CNTs in fiber matrices and a spatial embedment in fiber cores, respectively. Conductive networks were formed in the fibrous scaffolds after the inoculation of over 3% CNTs, and the increase in the conductivity could maintain the cell viabilities, induce the cell elongation, enhance the production of sarcomeric α-actinin and troponin I, and promote the synchronous beating of cardiomyocytes. Although the conductivity of blend fibers is slightly higher than that of coaxial fibers with the same CNT loadings, the lower exposures to CNTs resulted in higher cell viability, elongation, extracellular matrix secretion and beating rates for cardiomyocytes on coaxial fibers. Taken altogether, core-sheath fibers with loaded 5% of CNTs in the fiber cores facilitated the cardiomyocyte growth with a production of organized contractile proteins and a pulsation frequency close to that of the atrium. It is suggested that electrospun scaffolds that couple conductivity and fibrous structure considerations may provide optimal stimuli to foster cell morphology and functions for myocardial regeneration or establishment of in vitro cardiomyocyte culture platform for drug screening.
... The electrospinning was performed under 20 kV using a high-voltage statitron (Tianjing High Voltage Power Supply Co., Tianjing, China). Fibers were collected on an aluminum foil wrapped on a grounded rotating mandrel at a linear rate of around 15 m/s (Chen et al., 2010). The fibrous mats were folded perpendicularly to the fiber alignment and soaked completely with distilled water, followed by cryocutting into sections of 20 mm thickness using a cryostat microtome (Microme HM550 OMC, Thermo Fisher Scientific Inc., Waltham, MA). ...
... It is therefore advantageous to design orthopedic implants consisting of organized fibers to exploit these physiological and mechanical cues. In our recent study, a bulk nanocomposite was made out of nanofibers through layer-by-layer deposition of aligned composite fibers and hot pressing [12]. The hot-pressing process was aimed to maintain the fibrous structure and strengthen the fiber bondings, which were important to enhance the stress transfer and improve the mechanical properties. ...
... The hot-pressing process was aimed to maintain the fibrous structure and strengthen the fiber bondings, which were important to enhance the stress transfer and improve the mechanical properties. The layer-by-layer deposition of aligned fibers was aimed to mimic the mechanically anisotropic behavior of natural bone, and mechanical properties of hot-pressed composites could be quantitatively controlled by interlayer angles of the fiber deposition [12]. ...
... In situ grown HA/PDLLA composite fibers (IGC) were prepared from aligned electrospun PDLLA fibers grafted with gelatin as the induction sites for HA growth. Aligned PDLLA fibers were prepared as described previously with some modifications [12]. Briefly, PDLLA was dissolved in THF, and added in a 5 ml syringe attached with a circular-shaped metal needle as the nozzle. ...
In situ grown composite fibers of hydroxyapatite (HA) and poly(dl-lactide) with uniaxial distribution were deposited layer-by-layer followed by hot pressing to obtain fibrous composites. The tribological profiles were clarified at low amplitude oscillatory motion as potential orthopedic implants. The inoculation of HA nanoparticles into fibrous composites lowered the coefficients of friction (COFs) and wear rates, and the hardness of HA layers and rolling effect of HA particles further improved the wear resistance. The COFs and wear rates were significantly lower when fretting along the fiber orientation than those when the slide direction was perpendicular to the fiber alignment.
Due to lack of amino sugar with aging, people will suffer from various epidemic bone diseases called “undead cancer” by the World Health Organization. The key problem in bone tissue engineering that has not been completely resolved is the repair of critical large‐scale bone and cartilage defects. The chirality of the extracellular matrix plays a decisive role in the physiological activity of bone cells and the occurrence of bone tissue, but the mechanism of chirality in regulating cell adhesion and growth is still in the early stage of exploration. This paper reviews the application progress of chirality‐induced bionic scaffolds in bone defects repair based on “soft” and “hard” scaffolds. The aim is to summarize the effects of different chiral structures (L‐shaped and D‐shaped) in the process of inducing bionic scaffolds in bone defects repair. In addition, many technologies and methods as well as issues worthy of special consideration for preparing chirality‐induced bionic scaffolds are also introduced. We expect that this work can provide inspiring ideas for designing new chirality‐induced bionic scaffolds and promote the development of chirality in bone tissue engineering. This article is protected by copyright. All rights reserved
The well-aligned electrospun Poly (mphenylene isophthalamide) (PMIA) nanofibers reinforced Polylactic acid (PLA) composites is fabricated via hot-pressing. Scanning electron microscopy (SEM), differential scanning calorimeter/thermal gravimetric analyser (DSC-TGA) and Dynamic Mechnical Analysis (DMA) are used to characterize morphologies of the broken sections and properties of composites. The results show that the tensile breaking strength and initial modulus have been enhanced much compared to that of pure PLA. The remarkable improvement emerges at the load 38 wt.% of nanofibers with the tensile strength and initial modulus increase by ca. 235 % and ca. 149 %, respectively. The hot-press process did not damage the nanofibers figuration and there are appear cracks link together with nanofibers by increasing the nanofiber contents. The initial degradation temperature of nanofibers reinforced composites are lower than that of pure PLA, but the final residual rate of composites increases with the increase of nanofibers mass fraction. Both the storage modulus and loss modulus of the composites increased with the addition of PMIA nanofibers. The addition of 38 wt.% of nanofibers yields an increase of the storage modulus ca. 11 % and the loss modulus ca. 13 % at 40 °C. © 2019, Kauno Technologijos Universitetas. All rights reserved.
In this work, an experimental study was performed to investigate the shearing mechanical properties of short basalt fiber-reinforced polymer composite materials (SBFRP), and an optimized test method was developed. The following findings were obtained: (1) The optimized V-notched rail shear device and test method are reliable and valid, enabling the effective shear testing of samples similar to those tested in this study in the future. (2) The shearing failure cracks of SBFRPs can be classified into three types, namely, main cracks, coupling cracks, and micro-cracks. The micro-cracks, which originate from micro-slippage at the interfaces between the short fibers and the epoxy resin, initiate prior to the main cracks. (3) The existence of a critical value of the fiber volume fraction is proposed, above which a sample possesses a nonlinear deformation capacity by virtue of the initial micro-slippage at the fiber/matrix interfaces. Furthermore, a higher fiber volume fraction gives rise to a stronger nonlinear deformation capacity. (4) The shearing mechanical properties and other basic material attributes of SBFRPs with a fiber length of 3 mm are presented, thereby establishing a foundation for the theoretical study, finite-element analysis, and application and dissemination of SBFRPs. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46078.
We report the mechanical performance of α-FeOOH nanowire reinforced poly(vinyl alcohol) (PVA) composite nanofiber mat, fabricated using straightforward aqueous processing methods. Goethite (α-FeOOH) nanocrystals have a high elastic modulus and –OH rich surface, ensuring strong interactions with hydrophilic polymers and effective reinforcement. Needle-less electrospinning resulted in alignment of the nanowires along fibre axis, as confirmed by transmittance electron microscopy studies. Produced composite PVA nanofibers containing 10 wt% goethite nanoparticles exhibited an outstanding fivefold increase in Young's modulus and 2.5-fold improvement of tensile strength compared to mats of neat PVA. The addition of α-FeOOH had a significant influence on glass transition temperature indicating formation of interphase regions around nanowire inclusions. Observed properties are explained by nanowire grafting in the precursor solution, extensive interactions between the adsorbed PVA chains and the matrix and percolation of interphase regions at 10 wt% α-FeOOH. POLYM. COMPOS., 2016.
