Electrospun poly(hydroxybutyrate)/chitosan blend fibrous scaffolds for cartilage tissue engineering

In this study, polyhydroxybutyrate (PHB) was blended with chitosan (CTS), and electrospun in order to produce more hydrophilic fibrous scaffolds with higher mass loss rates for cartilage tissue engineering application. First, the effects of diverse factors on the average and distribution of fiber's diameter of PHB scaffolds were systematically evaluated by experimental design. Then, PHB 9 wt % solutions were blended with various ratios of CTS (5%, 10%, 15%, and 20%) using trifluoroacetic acid as a co‐solvent, and electrospun. The addition of CTS could decrease both water droplet contact angle from ～74° to ～67° and tensile strength from, ～87 MPa to ～31 MPa. According to the results, the scaffolds containing 15% and 20% CTS were selected as optimized scaffolds for further investigations. Mass loss percentage of these scaffolds was directly proportional to the amount of CTS. Chondrocytes attached well to the surfaces of these scaffolds. The findings suggested that PHB/CTS blend fibrous scaffolds have tremendous potentials for further investigations for the intended application. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44171.     

Development and characterization of bionanocomposites based on poly(3‐hydroxybutyrate) and cellulose nanocrystals for packaging applications

Poly(3‐hydroxybutyrate) (PHB)‐based bionanocomposites were prepared using various percentages of cellulose nanocrystals (CNCs) by a solution casting method. CNCs were prepared from microcrystalline cellulose using sulfuric acid hydrolysis. The influence of CNCs on PHB properties was evaluated using differential scanning calorimetry, Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetry and tensile testing. Vapor permeation and light transmission of the materials were also measured. Differential scanning calorimetric tests demonstrated that CNCs were effective PHB nucleation agents. Tensile strength and Young's modulus of PHB increased with increasing CNC concentration. Moreover, the PHB/CNC bionanocomposites exhibited reduced water vapor permeation compared to neat PHB and had better UV barrier properties than commodity polymers such as polypropylene. It was found that nanocomposites with 6 wt% of CNCs had the optimum balance among thermal, mechanical and barrier properties. © 2016 Society of Chemical Industry     

Green composites of poly(3‐hydroxybutyrate) and curaua fibers: Morphology and physical,thermal, and mechanical properties

In this article, we report the morphology and thermal, mechanical and physical properties of poly(3‐hydroxybutyrate) (PHB)/curaua composites containing triethyl citrate (TEC) as the plasticizer. The composites were prepared by mechanical mixing using pristine and chemically treated fibers (10 wt %) and TEC (30 wt %) and characterized by differential scanning calorimetry, dynamic mechanical analysis, X‐ray diffraction, small angle X‐ray scattering, polarized optical microscopy, scanning electron microscopy, tensile tests, impact resistance test, thermodilatometry, and thermal conductivity measurements. The curaua fibers acted as nucleating agent and strongly influenced the morphology of the crystalline phase of PHB, increasing the lamella thickness, decreasing the crystal size and inducing spherulite–axialite transition. These characteristics of the PHB crystalline phase determined all the properties of the composites. The tensile properties of the composites were comparable with those of neat PHB, while the impact resistance of composites was comparable with that of plasticized PHB. The higher heat capacity and thermal expansion coefficient and the lower thermal conductivity of the composites compared with neat PHB reflect the morphological changes in the PHB crystalline phase. The strategy of developing a green polymeric material from ecofriendly components exhibiting a good balance of properties by combining curaua fibers, TEC, and PHB was successful. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44676.     

Fabrication and characterization of hydrophilic poly(ε‐caprolactone)/pluronic P123 electrospun fibers

Poly(ε‐caprolactone) (PCL) has been widely investigated for tissue engineering applications because of its good biocompatibility, biodegradability, and mechanical properties; however hydrophobic nature of PCL has been a colossal obstacle toward achieving scaffolds which offer satisfactory cell attachment and proliferation. To produce highly hydrophilic electrospun fibers, PCL was blended with pluronic P123 (P123) and the resulted electrospun scaffolds physiochemical characteristics such as fiber morphology, thermal behavior, crystalline structure, mechanical properties, and wettability were investigated. Moreover molecular dynamic (MD) simulation was assigned to evaluate the blended and neat PCL/water interactions. Presence of P123 at the surface of electrospun blended fibers was detected using ATR‐FTIR analysis. P123 effectiveness in improving the hydrophilicity of the scaffolds was demonstrated by water contact angel which experienced a sharp decrease from 132° corresponding to the neat PCL to almost 0° for all blended samples. Also a steady increase in water uptake ratio was observed for blended fibers as P123 content increased. The 90/10 blend ratio had the maximum tensile strength, elongation at break and crystallinity percentage. Therefore 90/10 blend ratio of PCL/P123 can balance the mechanical properties and bulk hydrophilicity of the resulted electrospun scaffold and would be a promising candidate for tissue engineering application. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43345.     

Thermal and dynamic mechanical behavior of poly(lactic acid) (PLA)-based electrospun scaffolds for tissue engineering

Electrospun scaffolds can find numerous applications, including biomedical; for example, tissue engineering. Poly-L-lactic acid is considered suitable for these applications, but its low-thermal stability and its poor mechanical properties limit this polymer use. The aim of this work is to obtain a modulation of the final scaffolds characteristics such as fibers dimension, wettability, elasticity, and resistance to rupture through the choice of the polymers to be electrospun. Different electrospun scaffolds containing gelatin, Poly-DL-lactic acid, different percentages of cellulose nanocrystals and an elastin peptide have been produced. Thermal stability, physical structure, and its mechanical behavior have been studied. Results suggest that the electrospun scaffolds show better thermal and mechanical properties than bulk materials; that is, the scaffolds with the best hydrophilic and thermomechanical properties are the samples containing 3% (wt/wt) of CNCs and elastin peptide.     

Crystallization behavior and mechanical properties of an electrospun ethanol‐mediated poly(ethylene terephthalate) fibrous membrane

A simple approach for preparing electrospun poly(ethylene terephthalate) (PET) fibrous membranes with excellent spinnability and mechanical properties is introduced in this article. To enhance the electrospinnability of PET, a small content of ethanol was incorporated into a 16 wt % PET solution. The effects of ethanol on the solution properties, mechanical properties and crystallization properties and the related morphology were systematically evaluated. The conductivity (κ) measurement indicated that ethanol could obviously improve κ of the PET solution; this correlated well with the morphology of fibers. Scanning electron microscopy images showed that the diameter of the fibers decreased with increasing solution κ. The tensile strength of the PET fibrous membrane increased 1.8 times through the blending of 2.5 vol % ethanol with the PET solution. The differential scanning calorimetry results showed that the crystallinity was improved when the ethanol content increased; this was beneficial to the enhancement of the tensile strength. The glass‐transition temperature and melting temperature increased slightly, but the cold‐crystallization peak shifted to a lower temperature with increasing ethanol content (<3.75 vol %); this was attributed to the increasing in the oriented degree. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42341.     

Crosslinked carboxylated SBR composites reinforced with chitin nanocrystals

This study aims to develop and characterize the nanocomposites using sulfur cross-linked carboxylated styrene-butadiene rubbers (S-xSBR) as the matrix and chitin nanocrystals (CNCs) as nanofillers. The composites’ morphology and properties were examined by light transmittances, fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), dynamic mechanical analysis (DMA), thermo gravimetric analyzer (TGA), and tensile properties determination. The addition of CNCs has slight effect on transparency of the composite films. FTIR data confirm the interfacial interactions between CNCs and S-xSBR via hydrogen bonds. CNCs are uniformly dispersed in the matrix from SEM result. The addition of CNCs can significantly improve the tensile strength and modulus both in static and dynamic states. The tensile modulus and tensile strength of S-xSBR/CNCs composites with the 4 wt.% CNCs is 62.5 % and 97.6 % higher than that of pure S-xSBR. The storage modulus, glass transition temperature, and the thermal stability of the composites are higher than those of the neat S-xSBR. The mechanical properties of the composite films are water-responsive, as the swollen samples exhibit obviously decreased strength and modulus. The greatest mechanical contrast is shown in the S-xSBR/CNCs composites with 2 wt.% CNCs loading whose tensile modulus decrease from 60.4 to 6.1 MPa after swelling equilibrium. The significant reinforcement effect of CNCs on S-xSBR is attributed to the unique structure of CNCs and the interfacial interactions in the composite.     

Biodegradable nanofibrous membrane of zein/silk fibroin by electrospinning

BACKGROUND: Electrospinning of natural polymers offers a promising approach to generate nanofibers with a similar fibrillar structure to that of native extracellular matrix. In the present work, zein/silk fibroin (SF) blends were electrospun with formic acid as solvent to fabricate bicomponent nanofibrous scaffolds for biomedical applications. RESULTS: The zein/SF electrospun nanofibers had a smaller diameter and narrower diameter distribution than pure zein nanofibers, and the average diameter gradually decreased from 265 to 230 nm with increasing SF content in the blend. The predominant presence of α‐helix zein structure and random coil form of silk I in blend fibrous membranes was confirmed from Fourier transform infrared spectral and wide‐angle X‐ray diffraction data, while conversion to the β‐sheet structure of SF was also detected. The tensile strength of the zein/SF fibrous membranes was improved as the content of SF in the blend fibers increased. A preliminary study of in vitro degradation and cytotoxicity evaluated by MTT assay indicated that biodegradable zein/SF fibrous membranes did not induce cytotoxic effects in an L929 mouse fibroblast system. CONCLUSION: Biodegradable zein/SF fibrous membranes with good mechanical properties and cytocompatibility combine the beneficial characteristics of the individual components and may be useful for biomedical applications. Copyright © 2009 Society of Chemical Industry     

Modified cellulose nanocrystals enhancement to mechanical properties and water resistance of vegetable oil-based waterborne polyurethane

Environmentally friendly and lightweight silylated cellulose nanocrystal (SCNCs)/waterborne polyurethane (WPU) composite films that exhibit excellent mechanical properties and water resistance were prepared. The cellulose nanocrystals (CNCs) of the filamentous structure were surface-modified by γ-aminopropyltriethoxysilane (APTES) and then introduced into a castor oil-based aqueous polyurethane (WPU) matrix by in situ polymerization. The morphology and silylation degree of CNCs were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier infrared transform spectroscopy at different APTES concentrations. The results showed that the surface of the nanocellulose crystal has the best silylation morphology and thermal stability with incorporation of 6 wt % APTES. The thermal stability, mechanical properties, surface morphology, and water resistance of the nanocomposites were investigated by TGA, tensile test, SEM and optical contact angle, water absorption test, and mechanical property test after immersed in water. It was found that the effective introduction of modified CNCs resulted in a significant increase in tensile strength at high levels, and the thermal stability and hydrophobicity of the material were improved simultaneously, reaching the percolation threshold at a 0.50 wt % SCNCs as determined theoretically. This study provided an approach to the design and development of surface-modified CNCs/vegetable oil-based polymer composites by using an appropriate concentration of silane coupling agent to modify CNCs and improve the compatibility between nanocellulose and vegetable oil-based polymer matrices. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48228.     

Preparation and characterization of poly(glycerol sebacate)/cellulose nanocrystals elastomeric composites

Poly(glycerol sebacate) (PGS) is one of the new elastomers used for soft tissue engineering, while improving its limited mechanical strength is the biggest challenge. In this work, a novel biodegradable elastomer composite PGS/cellulose nanocrystals (CNCs) was prepared by solution‐casting method and the mechanical properties, sol–gel contents, crosslink density, and hydrophilic performance were characterized. The thermal and degradation properties of composites were also investigated. Results show that the addition of CNCs into PGS resulted a significant improvement in tensile strength and modulus, as well as the crosslink density and the hydrophilicity of PGS. When the CNCs loading reached 4 wt %, the tensile strength and modulus of the composite reached 1.5 MPa and 1.9 MPa, respectively, resulting 204% and 158% increase compared to the pure PGS. Prolonging the curing time also improved the strength of both the neat PGS and PGS/CNCs composites according to the association and shift of hydroxy peaks around 3480 cm^?1. DSC results indicate that the addition of CNCs improved both the crystallization capacity and moving capability of PGS molecular chain. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42196.     

Synthesis of polyamide 6/11 copolymers and their use as matrix polymer in wood‐plastic composites

The goal of this study was to investigate the synthesis and the resulting thermal, rheological, and mechanical properties of polyamide 6/11 copolymers (PA 6/11) as a function of their composition and to further investigate their usability as matrix polymers for wood‐plastic composites (WPC). A significant composition dependency of the melting temperature was found due to the hindered crystallization of the PA 6/11 copolymers with increasing content of the minor component. In result, the lowest melting temperature of the copolymers was measured at 120 °C for 40 wt % of ?‐caprolactam (PA 6/11‐40/60) by DSC analysis. Due to its low melting point and feasible mechanical properties, a copolyamide with 70 wt % of ?‐caprolactam (PA 6/11‐70/30) was chosen as matrix material for the processing of WPC. Incorporation of 30 wt % of wood fibers into PA 6/11‐70/30 caused a significant increase in tensile modulus and a decrease in tensile strength and strain at break. However, the processed WPC still showed an exceptional ductility with a strain at break of 15 to 20%. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44155.     

Cellulose acetate ultrafiltration membranes reinforced by cellulose nanocrystals: Preparation and characterization

Cellulose nanocrystals (CNCs) were used as a sustainable additive to improve the hydrophilicity, permeability, antifouling, and mechanical properties of blend membranes. Different CNC loadings (0–1.2 wt %) in cellulose acetate (CA) membranes were studied. The blend membranes were prepared by a phase‐inversion process, and their chemical structure and morphological properties were characterized by attenuated total reflectance–Fourier transform infrared spectroscopy, scanning electron microscopy, porosity, and mean pore size and contact angle measurement. The blend membranes became more porous and more interconnected after the addition of CNCs. The thickness of the top layer decreased and a few large holes in the porous substrate appeared with increasing CNC loading. In comparison with the pure CA membranes, the pure water flux of the blend membranes increased with increasing CNC loading. It reaches a maximum value of 76 L m^?2 h^?1 when the CNC loading was 0.5 wt %. The antifouling properties of the CA membrane were significantly improved after the addition of CNCs, and the flux recovery ratio value increased to 68% with the addition of 0.5 wt % CNCs. In comparison with that of the pure CA membranes, the tensile strength of the composite membranes increased by 47%. This study demonstrated the importance of using sustainable CNCs to achieve great improvements in the physical and chemical performance of CA ultrafiltration membranes and provided an efficient method for preparing high‐performance membranes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43946.     

Point‐bonded electrospun polystyrene fibrous mats fabricated via the addition of poly(butylacrylate) adhesive

Because of poor mechanical strength, applications of electrospun polystyrene (PS) fibrous mats are quite limited. The introduction of various concentrations of poly (butylacrylate) adhesives (PBAs) into PS solutions led to the fabrication of point‐bonded electrospun PS fibrous mats with good mechanical strength. The morphologies of PS/PBA fibers with varying PBA content (0?50 wt%) were investigated using scanning electron microscopy (SEM), and the results were compared with pure PS and PBA fibers fabricated with various solvents. SEM images indicated that point‐bonded PS/PBA fibers were uniformly distributed with an average diameter of 1–2 μm. On increasing concentration of PBA up to 20 wt%, porous PS/PBA fibrous mats were obtained. However, solid films were formed at very high concentrations of PBA. The Young's modulus and tensile strength of PS/PBA fibrous mats increased up to 52.4 and 2.7 MPa, respectively. The resultant enhancement of the mechanical properties of PS fibrous mats on addition of PBA increases the number of potential applications of these materials. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Nanocomposites of poly(propylene carbonate) reinforced with cellulose nanocrystals via sol‐gel process

Cellulose nanocrystals (CNCs) organogels were first produced from aqueous dispersion through solvent exchange of CNCs to acetone via a simple sol‐gel process. After mixing the organogels with poly(propylene carbonate) (PPC) in dimethylformamide followed by solution casting, green nanocomposites were obtained with CNCs well dispersed in PPC polymer matrix which was confirmed by scanning electron microscopy observations. Differential scanning calorimeter analysis revealed that glass transition temperature of the nanocomposites was slightly increased from 34.0 to 37.4°C. Tensile tests indicated that both yield strength and Young's modulus of CNCs/PPC nanocomposites were doubled by adding 10 wt % CNCs. However, poor thermal stability of PPC occurred after incorporating with CNCs due to the thermo‐sensitive sulfate groups located on the surface of CNCs. Furthermore, PPC became more hydrophilic because of the inclusion of CNCs according to the water contact angle measurement. The enhanced mechanical and hydrophilic properties, coupled with the inherent superior biocompatibility and degradability, offered CNCs/PPC composites potential application in biomedical fields. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40832.     

Structure, mechanical properties and degradation behaviors of the electrospun fibrous blends of PHBHHx/PDLLA

Blends of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) and poly(d,l-lactic acid) (PDLLA) with different ratios were fabricated into fibrous membranes by electrospinning processes. Suggested by DSC, WAXD, and SAXS results, the molecular chains of PHBHHx and PDLLA were partially mixed in the amorphous phase, PDLLA didn’t affect the growth of PHBHHx crystalline phase, and PDLLA was excluded from PHBHHx lamella stacks, i.e. in form of interstack segregation, in the blend fibrous matrix. The mechanical properties of the electrospun fibrous membranes depended on the orientation of fibers in the membranes. The electrospun membranes had higher elongation; furthermore, the tensile strength and modulus of the fibers within the membranes were higher than the corresponding cast membranes. As the content of PDLLA increased, the electrospun fibrous membranes of the blends showed higher elongation and lower tensile modulus due to the decreased number of lamellae. According to the change of molecular weight distribution, both PHBHHx and PDLLA portions in the electrospun blend membranes followed bulk erosion and PDLLA degraded faster than PHBHHx during the degradation process. The morphology change of the electrospun fibrous blends during the hydrolytic degradation indicated that the degradation behaviors were strongly influenced by the miscibility and the structural phase segregation of PHBHHx/PDLLA blend in the electrospun fibers.     

Preparation and properties of biocomposites based on jute fibers and blend of plasticized starch and poly(β‐hydroxybutyrate)

In this work, preparation and properties of biocomposites based on jute fibers and blend of plasticized starch and poly(β‐hydroxybutyrate) (PHB) have been investigated. Different amounts of glycerol and aliphatic polyesters (PHB) have been added to native starch to obtain a processable biodegradable matrix. In the same way natural jute fibers up to 30 wt % loading were added to improve the mechanical and thermal stability of the material. Tensile mechanical, thermal, and thermomecahnical analyses have been performed to characterize the ensuing materials. Significant enhancement in the mechanical properties and water sensitivity were noted by the addition of 8 wt % PHB. The fibers incorporation into the biopolymer matrix brings about an increase in both the mechanical strength and modulus as much higher as the fibers loading is important. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Crystallization,mechanical, and fracture behavior of mullite fiber‐reinforced polypropylene nanocomposites

This study describes the reinforcement effect of surface modified mullite fibers on the crystallization, thermal stability, and mechanical properties of polypropylene (PP). The nanocomposites were developed using polypropylene‐grafted‐maleic anhydride (PP‐g‐MA) as compatibilizer with different weight ratios (0.5, 1.0, 1.5, 2.5, 5.0, and 10.0 wt %) of amine functionalized mullite fibers (AMUF) via solution blending method. Chemical grafting of AMUF with PP‐g‐MA resulted in enhanced filler dispersion in the polymer as well as effective filler‐polymer interactions. The dispersion of nanofiller in the polymer matrix was identified using scanning electron microscopy (SEM) elemental mapping and transmission electron microscopy (TEM) analysis. AMUF increased the Young's modulus of PP in the nanocomposites up to a 5 wt % filler content, however, at 10 wt % loading, a decrease in the modulus resulted due to agglomeration of AMUF. The impact strength of PP increased simultaneously with the modulus as a function of AMUF content (up to 5 wt %). The mechanical properties of PP‐AMUF nanocomposites exhibited improved thermal performance as compared to pure PP matrix, thus, confirming the overall potential of the generated composites for a variety of structural applications. The mechanical properties of 5 wt % of AMUF filled PP nanocomposite were also compared with PP nanocomposites generated with unmodified MUF and the results confirmed superior mechanical properties on incorporation of modified filler. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43725.     

Enhanced thermal stability of biomedical thermoplastic polyurethane with the addition of cellulose nanocrystals

Freeze‐dried cellulose nanocrystals (CNCs) were dispersed in the thermoplastic polyurethane [Pellethane 2363‐55D (P55D)] by a solvent casting method to fabricate CNC‐reinforced nanocomposites. This study demonstrated that the addition of small amounts (1–5 wt %) of CNCs to P55D increased the thermal degradation temperature while maintaining a similar stiffness, strength, and elongation of the neat P55D. CNC additions to P55D did not alter the glass‐transition temperature, but the onset decomposition temperature was shifted from 286 to 327°C when 1 wt % CNCs was dispersed in the matrix. The higher onset decomposition temperature was attributed to the formation of hydrogen bonds between the hydroxyl groups on the CNC surface and urethane groups in the hard block of P55D. The ultimate tensile strength and strain to failure (ε_f) of the nanocomposites were minimally affected by additions up to 5 wt % CNCs, whereas the elastic modulus was increased by about 70%. The observation that ε_f was unchanged with the addition of up to 5 wt % CNCs suggested that the flow/sliding of the hard blocks and chains were not hindered by the presence of the CNCs during plastic deformation. The ramifications of this study was that CNC additions resulted in wider processing temperatures of P55D for various biomedical devices while maintaining a similar stiffness, strength, and elongation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41970.     

Crosslinked PVA nanofibers reinforced with cellulose nanocrystals: Water interactions and thermomechanical properties

Acid‐catalyzed vapor phase esterification with maleic anhydride was used to improve the integrity and thermo‐mechanical properties of fiber webs based on poly(vinyl alcohol), PVA. The fibers were produced by electrospinning PVA from aqueous dispersions containing cellulose nanocrystals (CNCs). The effect of esterification and CNC loading on the structure and solvent resistance of the electrospun fibers was investigated. Chemical characterization of the fibers (FTIR, NMR) indicated the formation of ester bonds between hydroxyl groups belonging to neighboring molecules. Thermomechanical properties after chemical modification were analyzed using thermal gravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. An 80% improvement in the ultimate strength was achieved for CNC‐loaded, crosslinked PVA fiber webs measured at 90% air relative humidity. Besides the ultra‐high surface area, the composite PVA fiber webs were water resistant and presented excellent mechanical properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40334.