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1.
In this work, flexible nanofibrous membranes (mats) of poly(ethylene oxide) (PEO) with and without multiwall carbon nanotubes (MWNTs) were fabricated by electrospinning. The effects of annealing and MWNT concentration on mat morphology, MWNT dispersion within the nanofibers, and the mechanical properties of electrospun mats were studied. Annealing temperatures ranged from 60 °C to 64 °C [near the melting temperature (64 °C via differential scanning calorimetry)] for 4 minutes. Samples were annealed with and without applied tension (constrained and unconstrained annealing). Annealing at the highest temperature (64 °C), before the loss of fibrous morphology, significantly improved fiber–fiber bonding and therefore the tensile strength of the mats. Compared with unconstrained annealing, constrained annealing introduced fiber alignment (and therefore molecular orientation) along the tensile axis (direction of constraint) during annealing and resulted in a significant increase in modulus for all samples (with and without MWNTs). The use of constrained annealing may be a facile approach to enhance modulus in nanofibrous mats while maintaining high porosity. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 787–796  相似文献   

2.
In this work, three-dimensional (3D) printing system based on fused deposition modeling (FDM) is used for the fabrication of conductive polymer nanocomposites. This technology consists in the additive multilayer deposition of polymeric nanocomposite based on poly(lactic acid) (PLA) and graphene by means of a in house made low-cost commercial bench-top 3D printer. Further, 3D printed PLA/graphene nanocomposites containing 10 wt% graphene in PLA matrix were characterized for their mechanical, electrical and electromagnetic induction shielding properties of the nanocomposite. Furthermore X-ray computed micro-tomography analyses showed that printed samples have good dimensional accuracy and are significantly closer to the predefined design and the results of scanning electron microscopy (SEM) printed samples showed a uniform dispersion of graphene in PLA matrix The proposed material has uniquely advantageous when implemented in 3D printed structures, because incorporation of multifunctional graphene has been shown to substantially improve the properties of the resulting nanocomposite.  相似文献   

3.
The cellulose fiber was extracted from the abandoned crop sugarcane bagasse (SCB) by means of chemical treatment methods. Poly(lactic acid) (PLA) bio‐based composites with SCB were prepared through fused deposition modeling (FDM) 3D‐printing technology, and the morphologies, mechanical properties, crystallization properties, and thermal stability of 3D‐printed composites were investigated. Compared with the neat PLA, the incorporation of SCB into PLA reduces the tensile strength and flexural strength of 3D‐printed samples but increases the flexural modulus. The difference in tensile performance and bending performance is that the tensile strength of 3D‐printed samples is best when the SCB content is 6 wt%, while the flexural modulus continuously decreases as the SCB content increases. Furthermore, the effects of various printing methods on the tensile performance of 3D‐printed samples were explored via modifying G‐code of 3D models. The results indicate that the optimum SCB fiber content is identical for all printing methods except method “vertical.” Due to the fibers and molecular chains are oriented to varying degrees with altering raster angle in 3D‐printed samples, the fully oriented sample printed by method “parallel” has a better tensile strength. Besides, SCB exhibits enough high thermal decomposition temperature to meet requirements for melt extrusion processing of PLA composites, and SCB fiber is capable of promoting the crystallization of PLA.  相似文献   

4.
Cellulose nanowhiskers (CNW) extracted from plant fibers exhibit remarkable properties that make them suitable for use in the development of bionanocomposites. CNW have demonstrated the capability to enhance the properties of a polymer matrix at low filler loading. In this study, poly (lactic acid) (PLA) bionanocomposites were prepared using the solution casting technique, by incorporating the PLA with the CNW obtained from an oil palm empty fruit bunch (OPEFB). Fourier transform infrared spectroscopy showed no significant changes in the PLA peak positions, which indicates that incorporating the CNW into the PLA did not result in any significant changes in the chemical structure of the PLA. Thermogravimetric analysis, on the other hand, revealed that the bionanocomposites (PLA-CNW) had better thermal stability than the pure PLA. The tensile strength of PLA-CNW increased by 84% with the addition of 3 parts of CNW per hundred resins (phr), and decreased thereafter. Moreover, a linear relationship was observed between the Young's modulus and CNW loading. Elongation at break, however, decreased with the addition of 1-phr CNW, and remained constant with further addition. Transmission electron microscopy revealed that agglomeration of CNW occurred at 5-phr loading, consistent with the tensile strength results. Overall, the CNW obtained from OPEFB can enhance the tensile and the thermal properties of bionanocomposites.  相似文献   

5.
3D printing technologies permits to produce functional parts with complex geometries, optimized topologies or enhanced internal structures. The relationship between mechanical performance and manufacturing parameters should be exhaustively analyzed to warrant the long term success of printed products. In this work, the mechanical performance of filaments based on acrylonitrile butadiene styrene (ABS), polylactic acid (PLA) and polylactic acid/polyhydroxyalkanoate (PLA/PHA) was investigated and also compared with their corresponding 3D printed samples. In general, the specimen dimensional deviations were found to be within the tolerances defined by the standard testing protocols. Density values revealed a high level of filament fusion promoting a nearly solid internal structure. The filaments exhibited improved tensile performance with respect to their corresponding printed samples. Tensile and bending performance looked quite independent of the raster angle. Izod impact behavior was increased, for ABS systems printed with the ±45° raster orientation. Quasi-static fracture tests displayed improved crack initiation resistance with the 0°/90° raster angle. The crack propagation observed for the ±45° specimens, through the bonding of the inter-layers, suggests weak entanglements.  相似文献   

6.
Using pyromelliticdianhydride (PMDA) and polyfunctional epoxy ether (PFE) as branching agent, long chain branching stereocomplex poly(L‐lactide)s and poly(D‐lactide)s was prepared by reactive processing, respectably. Then stereocomplex poly(lactide)s of long chain branching PLLA and PDLA (sc‐PLA/BA) was prepared by solution blending and its fabricated the vascular stents via 3D‐printing.The effects of branching structure on melt crystallization behavior of sc‐PLA/BA investigated by DSC. The influence of the branching agent content on the crystallization ability of samples shows a bell‐shaped relationship, there is a maximum point when the branching agent content is1.5 wt%. When the branching agent content is less than 1.5 wt%, the crystallization ability of the sample increased with the increasing of branching agent content. When the branching agent content exceeded than 1.5 wt%, the crystallization ability of the samples decreased with branching agent content increasing. Such behavior is as the linear PLA branched to dendrite configuration, the enrichment of segments around branching structure within branched chains promoted its nucleation. But the high degree of branching caused inter‐ or intrachians entanglement which obstructed the segments movement and growth into the crystals. The half‐time of crystallization (t1/2) of the samples decreased from 6 minutes for initial sc‐PLA/BA‐0 to 3 minutes of sc‐PLA/BA‐1.5 wt% at 163°C. POM results indicated that nucleation density of sc‐PLA/BA significantly increased with the branching agent increasing. Moreover, mechanical testing demonstrated that forming branching structure could be an effective modification of the mechanical properties for sc‐PLA, its tensile strength and modulus increases from 57.3 MPa and 2.02 GPa to 70.4 MPa and 3.31 GPa, respectively. TGA results analyzed by FWO method and Kissinger method, indicated the apparent activation energy of sc‐PLA/BA samples increases from 96.8 to 113.3 kJ/mol, suggesting the improvement of heat resistance. The CCK‐8 assay, ALP assay and cell Live/Dead assay results indicated that sc‐PLA with branching structure presented very low cell cytotoxicity. Therefore, the long chain branching sc‐PLA matrix with branching agent could effectively improve its crystallization abilities, mechanical properties, heat resistance and biocompatibilities.  相似文献   

7.
Poly(lactic acid)‐grafted multiwalled carbon nanotubes (MWNT‐g‐PLA) were prepared by the direct melt‐polycondensation of L ‐lactic acid with carboxylic acid‐functionalized MWNT (MWNT‐COOH) and then mixed with a commercially available neat PLA to prepare PLA/MWNT‐g‐PLA nanocomposites. Morphological, thermal, mechanical, and electrical characteristics of PLA/MWNT‐g‐PLA nanocomposites were investigated as a function of the MWNT content and compared with those of the neat PLA, PLA/MWNT, and PLA/MWNT‐COOH nanocomposites. It was identified from FE‐SEM images that PLA/MWNT‐g‐PLA nanocomposites exhibit good dispersion of MWNT‐g‐PLA in the PLA matrix, while PLA/MWNT and PLA/MWNT‐COOH nanocomposites display MWNT aggregates. As a result, initial moduli and tensile strengths of PLA/MWNT‐g‐PLA composites are much higher than those of neat PLA, PLA/MWNT, and PLA/MWNT‐COOH, which stems from the efficient reinforcing effect of MWNT‐g‐PLA in the PLA matrix. In addition, the crystallization rate of PLA/MWNT‐g‐PLA nanocomposites is faster than those of neat PLA, PLA/MWNT, and PLA/MWNT‐COOH, since MWNT‐g‐PLA dispersed in the PLA matrix serves efficiently as a nucleating agent. It is interesting that, unlike PLA/MWNT nanocomposites, surface resistivities of PLA/MWNT‐g‐PLA nanocomposites did not change noticeably depending on the MWNT content, demonstrating that MWNTs in PLA/MWNT‐g‐PLA are wrapped with the PLA chains of MWNT‐g‐PLA. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

8.
Biopolymers are widely available, low-/nontoxic, biodegradable, biocompatible, chemically versatile, and inherently functional, making them highly potential for a broad range of applications such as biomedicine, food, textile, and cosmetics. 3D printing (3DP) is capable of fabricating some customized, complex material structures composed of single or multiple material constituents that cannot be achieved by conventional methodologies (e.g. internal structures design); thus, 3DP can greatly expand the application of biopolymer materials. This review presents a comprehensive survey of the latest literature in 3DP technology for materials from biopolymers such as polysaccharides and proteins. The most commonly used 3DP techniques (i.e. inkjet printing, extrusion-based printing, stereolithography, selective laser sintering, and binder jetting) in biomedical and food fields are discussed. Critical factors affecting the quality and accuracy of 3D-printed constructs, including rheological characteristics, printing parameters (e.g. printing rate, and nozzle diameter, movement rate, and height), and post-printing processes (e.g. baking, drying, and crosslinking) are analyzed. The properties and the emerging applications of 3D-printed biopolymer materials in biomedical, food, and even wider applications (e.g. wastewater treatment and sensing) are summarized and evaluated. Finally, challenges and future perspectives are discussed. This review can provide insights into the development of new biopolymer-based inks and new biopolymer-based 3D-printed materials with enhanced properties and functionality.  相似文献   

9.
Oriented poly(vinylidene fluoride) (PVDF) films consisting of β crystals were prepared by the solid‐state coextrusion (SC) of a gel film near the melting temperature (Tm) and by conventional cold tensile drawing (TD) of a melt‐quenched film. These films were annealed over the temperature range of 75–190 °C (below and above the static Tm) while the sample length was kept constant or constant loads were applied. After annealing with the sample length kept constant, the dynamic Young's modulus markedly decreased because of the relaxation of oriented amorphous chains, as shown by infrared spectroscopy. In contrast, annealing under a constant load improved the chain orientation in both the crystalline and amorphous regions, resulting in an increase in the modulus from an initial 10.5 to 14.3 GPa for the SC and from an initial 3.3 to 4.8 GPa for the TD. The SC, annealed at 190 °C with a constant load corresponding to an initial tension of 200 MPa, exhibited an extreme crystalline‐chain orientation of 0.998 and a modulus of 14.3 GPa, among the highest values ever reported for PVDF. Although the remanent polarization (Pr) of the TD increased slightly from the initial 62 to 68 mC/m2, Pr of the SC stayed constant at 100 mC/m2 independently of the annealing conditions. This suggests that the Pr value of 100 mC/m2 approached the equilibrium value for this PVDF sample containing 3.5 mol % structural defects. Therefore, although the modulus and Pr of the TD increased slightly with annealing, the maximum values achieved by annealing were markedly lower than those of the SC and annealed SC. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1701–1712, 2003  相似文献   

10.
Sustainable materials have slowly overtaken the nanofiber research field while the tailoring of their properties and the upscaling for industrial production are some of the major challenges. We report preparation of nanofibers that are bio-based and biodegradable prepared from poly (butylene succinate) (PBS) with the incorporation of nanofibrillated cellulose (NFC) and graphene nanoplatelets (GN). NFC and GN were combined as hybrid filler, which led to the improved morphological structure for electrospun nanofibers. A needleless approach was used for solution electrospinning fabrication of nanofiber mesh structures to promote application scalability. The polymer crystallization process was examined by differential scanning calorimetry (DSC), the thermal stability was evaluated by thermal gravimetric analysis (TGA), while the extensive investigation of the nanofibers structure was carried out with scanning electron microscopy (SEM) and atomic force microscopy (AFM). NFC and GN loadings were 0.5 and 1.0 wt %; while poly (ethylene glycol) (PEG) was employed as a compatibilizer to enhance fillers’ interaction within the polymer matrix. The interactions in the interface of the fillers and matrix components were studied by FTIR and Raman spectroscopies. The hybrid filler approach proved to be most suitable for consistent and high-quality nanofiber production. The obtained dense mesh-based structures could have foreseeable potential application in biomedical field like scaffolds for the tissue and bone recovery, while other applications could focus on filtration technologies and smart sensors.  相似文献   

11.
In this article, we report on the production by electrospinning of P3HT/PEO, P3HT/PEO/GO, and P3HT/PEO/rGO nanofibers in which the filler is homogeneously dispersed and parallel oriented along the fibers axis. The effect of nanofillers' presence inside nanofibers and GO reduction was studied, in order to reveal the influence of the new hierarchical structure on the electrical conductivity and mechanical properties. An in‐depth characterization of the purity and regioregularity of the starting P3HT as well as the morphology and chemical structure of GO and rGO was carried out. The morphology of the electrospun nanofibers was examined by both scanning and transmission electron microscopy. The fibrous nanocomposites are also characterized by differential scanning calorimetry to investigate their chemical structure and polymer chains arrangements. Finally, the electrical conductivity of the electrospun fibers and the elastic modulus of the single fibers are evaluated using a four‐point probe method and atomic force microscopy nanoindentation, respectively. The electrospun materials crystallinity as well as the elastic modulus increase with the addition of the nanofillers while the electrical conductivity is positively influenced by the GO reduction. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

12.
《Mendeleev Communications》2022,32(6):810-812
Three dimensional composite matrices based on poly-d,l-lactide filled with 5 or 10 wt% of nanocrystalline cellulose modified by poly(glutamic acid) were produced using pre- optimized 3D printing technique. The composites demonstrated good biocompatibility and significantly improved osteoconductive properties compared with the matrix without filler or the one filled with neat nanocrystalline cellulose.  相似文献   

13.
Novel ultrahigh molecular weight polyethylene (UHMWPE)/cellulose nanofiber (CNF) (F100CNFy) and UHMWPE/modified cellulose nanofiber (MCNFx) (F100MCNFxy) as‐prepared nanocomposite fibers were successfully prepared by gel‐spinning F100CNFy and F100MCNFxy gel solutions, respectively. CNF nanofillers with a specific surface area at 120 m2/g and a nanofiber diameter of 20 nm were successfully prepared by proper acid hydrolysis of cotton fibers using sulfuric acid solution. MCNFx nanofillers were prepared by grafting various contents of maleic anhydride grafted polyethylene (PEg‐MAH) onto CNF nanofillers. The ultimate σf value of the best‐prepared F100MCNFxy drawn fiber reached 4.5 GPa, which is about 67% higher than that of the UHMWPE drawn fiber prepared without the addition of any nanofiller. To understand the interesting ultradrawing, orientation, and tensile properties of F100CNFy and F100MCNFxy fibers, Fourier transform infrared, transmission electron microscopic analyses of the CNF and MCNFx nanofillers, and scanning electron microscopic analyses of profile surfaces of the etched drawn fibers were performed. This is the first work in this area of research wherein very small amounts of MCNFx nanofillers prepared from cotton fibers were efficiently used as nucleating agents to enhance the ultradrawing and ultimate tensile properties of F100MCNFxy fibers. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

14.
Silkworm silk/Poly(lactic acid) (silk/PLA) biocomposites with potential for environmental engineering applications were prepared by using melting compound methods. By means of Dynamic mechanical analysis (DMA), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), Coefficient of thermal expansion test, Enzymatic degradation test and Scanning electron microscopy (SEM), the effect of silk fiber on the structural, thermal and dynamic mechanical properties and enzymatic degradation behavior of the PLA matrix was investigated. As silk fiber was incorporated into PLA matrix, the stiffness of the PLA matrix at higher temperature (70-160 °C) was remarkably enhanced and the dimension stability also was improved, but its thermal stability became poorer. Moreover, the presence of silk fibers also significantly enhanced the enzymatic degradation ability of the PLA matrix. The higher the silk fiber content, the more the weight loss.  相似文献   

15.
The purposes of this paper are moving toward (a) the development of a new series of photoinitiators (PIs) which are based on the keto-coumarin (KC) core, (b) the introduction of light-emitting diodes (LEDs) as inexpensive and safe sources of irradiation, (c) the study of the photochemical mechanisms through which the new PIs react using different techniques such as Fourier transform infrared, UV–visible or fluorescence spectroscopy, and so on, (d) the use of such compounds (presenting good reactivity and excellent photopolymerization initiating abilities) for two specific and high added value applications: 3D printing (@405 nm) and preparation of thick glass fiber photocomposites with excellent depth of cure, and finally (e) the comparison of the performance of these KC derivatives versus other synthesized coumarin derivatives. In this study, six well-designed KC derivatives ( KC-C , KC-D , KC-E , KC-F , KC-G , and KC-H ) are examined as high-performance visible-light PIs for the cationic polymerization of epoxides as well as the free-radical polymerization of acrylates upon irradiation with LED@405 nm. Excellent polymerization rates are obtained using two different approaches: a photo-oxidation process in combination with an iodonium (Iod) salt and a photo-reduction process when associated with an amine (N-phenylglycine or ethyl 4-(dimethylamino)benzoate). High final reactive conversions were obtained. A full picture of the involved photochemical mechanisms is provided.  相似文献   

16.
In the present study, 3D FT-IR spectroscopic imaging measurements were applied to study the phase separation of a poly(3-hydroxybutyrate) (PHB)/poly(l-lactic acid) (PLA) (50:50 wt.%) polymer blend film. While in 2D projection imaging the z-dependent information is overlapped, thereby complicating the analysis, FT-IR spectro-micro-tomography, obtained from computed tomographic back projection calculations, results in distinct 3D chemical images that provide detailed information of phase separation of the two polymer components that are well separated.  相似文献   

17.
The influence of four types of plasticizers, dioctyl phthalate (DOP), dioctyl adipate (DOA), triacetyl glycerol (TAG) and polyadipate (PA), in the thermal and mechanical properties of Poly(3-hydroxybutyrate) (PHB), a highly crystalline biodegradable polyester, was evaluated in this work. The plasticizers were introduced alone or mixtures of them, using concentrations that varied from 5 to 30% wt. Their influence in some important polymer parameters as Tg, Tm and degree of crystallinity, and on its mechanical behavior, elongation and tensile strain were investigated. The best results were obtained for the sample with 30% TAG and that one using a binary mixture of plasticizers PA 20% and TAG 10%.  相似文献   

18.
The influence of the plasticizer content and film preparation procedure on the morphology, density, thermal and mechanical properties of cellulose acetate (CA) films plasticized with poly‐(caprolactone triol) (PCL‐T), were studied. Differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), scanning electron microscopy (SEM), wide‐angle X‐ray diffraction (WAXD) and infrared spectroscopy (FT‐IR) techniques were used. The films were prepared by dry‐casting CA and CA/PCL‐T in acetone or acetone/water solutions, which produced transparent and opaque films, respectively. In contrast to the transparent films, which were dense, the opaque films presented a porous morphology. However, the presence of PCL‐T reduced the opaque film porosity, increasing, in consequence, its bulk density. The TMA results revealed that PCL‐T reduced the glass transition temperature more significantly in the transparent than in opaque films. Only the transparent CA/PCL‐T films presented a melting temperature, that reduced with higher concentrations of PCL‐T, suggesting a higher ordering (crystallinity) when the films were prepared in the absence of water, as observed from WAXD curves. The mechanical properties also showed that the transparent films were more soft and tough than the opaque films. In summary, PCL‐T was a good plasticizer agent for CA films due to the presence of hydrogen bonds between the components (FT‐IR spectra). The presence of water in the dry casting process has a significant effect mainly on film morphology and mechanical properties. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

19.
Additive manufacturing is gaining a remarkable importance in manufacturing industries because of the ability to build parts with complex and intricate shapes. The most widely used material in additive manufacturing is the polymer. In this paper, circular textures have been 3D printed on the surface of Polylactic Acid (PLA) polymer using fused deposition modelling technique. Experiments were performed under dry and lubricated conditions by varying the texture size. The results were obtained for high and low speeds with varying loads of 10, 20, 30, 40 and 50 N. It was observed that coefficient of friction was minimum for texture T2 at both high and low speeds under dry sliding conditions. This is due to the less real area of contact than texture T1 and more effective formation of transfer film in case of texture T3. The entrapment of wear debris is more effective which helps in the formation of transfer layer that acts as solid lubricant. Under lubricated conditions, it was observed that for low speed, texture T3 has least coefficient of friction while at high speed texture T1 resulted in the minimum coefficient of friction. This is mainly due to the more retention of lubricating oil for texture T3 at low speed in comparison to the high speed. Surface analysis carried out for all the textures under dry sliding conditions revealed that the wear is mainly to adhesive and abrasive action.  相似文献   

20.
Nanofibers of poly (indene‐co‐pyrrole) (CInPy) have been synthesized, using a facile chemical oxidative polymerization reaction. The effect of copolymerization was examined in view of the individually synthesized homopolymer nanostructures of polyindene (PIn) and polypyrrole (PPy). Morphological details of CInPy, studied using scanning electron microscopy (SEM) and transmission electron microscopy, (TEM) reveal the appearance of dense cottony mess, comprising of fine fibers with an average diameter of 5–10 nm. Chemical structural analysis of CInPy, conducted using ultraviolet‐visible (UV‐Vis), Fourier transform infrared (FTIR), and nuclear magnetic resonance (NMR) spectroscopic techniques, reveals that both PIn and PPy are involved in the formation of copolymer organization. Fluorescence properties of nanosized copolymer are observed in the blue region, with emission λmax placed at 395 nm. Conductivity of copolymer nanofibers (2.4 × 10?3 S/cm) is consistent with the morphology and thermal stability properties of integral homo‐polymers. Improved thermal stability and processability along with the enhanced optical and electrical properties of copolymer nanostructures outfit it as a better promising material in optoelectronic and light emitting nanodevices, with reference to nanosized PIn and PPy. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

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