Biocompatible ternary nanocomposites based on poly(ether ether ketone) (PEEK)/poly(ether imide) (PEI) blends reinforced with bioactive titanium dioxide (TiO2) nanoparticles were fabricated via ...ultrasonication followed by melt-blending. The developed biomaterials were characterized using FT-IR, SEM, XRD, DSC, TGA, and DMA. Further, their water-absorption, tensile, tribological, dielectric, and antibacterial properties were evaluated. PEI acts as a coupling agent, since it can interact both with PEEK via π–π stacking and polar interactions as well as with the nanoparticles through hydrogen bonding, as corroborated by the FT-IR spectra, which resulted in a homogeneous titania dispersion within the biopolymer blend without applying any particle surface treatment or polymer functionalization. A change from promotion to retardation in the crystallization rate of the matrix was found with increasing TiO2 concentration, while its crystalline structure remained unaltered. The nanoparticles stiffened, strengthened, and toughened the matrix simultaneously, and the optimal properties were achieved at 4.0 wt % TiO2. More interesting, the tensile properties were retained after steam sterilization in an autoclave or exposure to a simulated body fluid (SBF). The nanocomposites also displayed reduced water absorption though higher thermal stability, storage modulus, glass transition temperature, dielectric constant, and dielectric loss compared to the control blend. Further, remarkable enhancements in the tribological properties under both SBF and dry environments were attained. The nanoparticles conferred antibacterial action versus Gram-positive and Gram-negative bacteria in the presence and the absence of UV light, and the highest inhibition was attained at 4.0 wt % nanoparticle concentration. These nanocomposites are expected to be used in long-term load-bearing implant applications.
Poly(3-hydroxybutyrate) (PHB)-based bionanocomposites incorporating different contents of ZnO nanoparticles were prepared via solution casting technique. The nanoparticles were dispersed within the ...biopolymer without the need for surfactants or coupling agents. The morphology, thermal, mechanical, barrier, migration and antibacterial properties of the nanocomposites were investigated. The nanoparticles acted as nucleating agents, increasing the crystallization temperature and the degree of crystallinity of the matrix, and as mass transport barriers, hindering the diffusion of volatiles generated during the decomposition process, leading to higher thermal stability. The Young's modulus, tensile and impact strength of the biopolymer were enhanced by up to 43%, 32% and 26%, respectively, due to the strong matrix-nanofiller interfacial adhesion attained via hydrogen bonding interactions, as revealed by the FT-IR spectra. Moreover, the nanocomposites exhibited reduced water uptake and superior gas and vapour barrier properties compared to neat PHB. They also showed antibacterial activity against both Gram-positive and Gram-negative bacteria, which was progressively improved upon increasing ZnO concentration. The migration levels of PHB/ZnO composites in both non-polar and polar simulants decreased with increasing nanoparticle content, and were well below the current legislative limits for food packaging materials. These biodegradable nanocomposites show great potential as an alternative to synthetic plastic packaging materials especially for use in food and beverage containers and disposable applications.
Castor oil (CO), which is a readily available, relatively inexpensive, and environmentally benign nonedible oil, has been successfully used as matrix material to prepare biocompatible and ...biodegradable nanocomposite films filled with chitosan (CS)-modified ZnO nanoparticles. The biocomposites were synthesized via a simple and versatile solution mixing and casting method. The morphology, structure, thermal stability, water absorption, biodegradability, cytocompatibility, barrier, mechanical, viscoelastic, antibacterial, and wound healing properties of the films have been analyzed. FT-IR spectra were used to obtain information about the nanoparticle–matrix interactions. The thermal stability, hydrophilicity, degree of porosity, water absorption, water vapor transmission rate (WVTR), oxygen permeability (Dk), and biodegradability of the films increased with the CS-ZnO loading. The WVTR and Dk data obtained are within the range of values reported for commercial wound dressings. Tensile tests demonstrated that the nanocomposites displayed a good balance between elasticity, strength, and flexibility under both dry and simulated body fluid (SBF) environments. The flexibility increased in a moist atmosphere due to the plasticization effect of absorbed water. The nanocomposites also exhibited significantly enhanced dynamic mechanical performance (storage modulus and glass transition temperature) than neat CO under different humidity conditions. The antibacterial activity of the films against Escherichia coli, Staphylococcus aureus, and Micrococcus luteus bacteria was investigated in the presence and the absence of UV light. The biocide effect increased progressively with the CS-ZnO content and was systematically stronger against Gram-positive cells. Composites with nanoparticle loading ≤5.0 wt % exhibited very good in vitro cytocompatibility and enabled a faster wound healing than neat CO and control gauze, hence showing great potential to be applied as antibacterial wound dressings.
Poly(propylene fumarate) (PPF)-based nanocomposites incorporating different amounts of polyethylene glycol-functionalized graphene oxide (PEG-GO) have been prepared via sonication and thermal ...curing, and their surface morphology, structure, thermal stability, hydrophilicity, water absorption, biodegradation, cytotoxicity, mechanical, viscoelastic and antibacterial properties have been investigated. SEM and TEM images corroborated that the noncovalent functionalization with PEG caused the exfoliation of GO into thinner flakes. IR spectra suggested the presence of strong hydrogen-bonding interactions between the nanocomposite components. A gradual rise in the level of hydrophilicity, water uptake, biodegradation rate, surface roughness, protein absorption capability and thermal stability was found upon increasing GO concentration in the composites. Tensile tests revealed improved stiffness, strength and toughness for the composites compared to unfilled PPF, ascribed to a homogeneous GO dispersion within the matrix along with a strong PPF/PEG-GO interfacial adhesion via polar and hydrogen bonding interactions. Further, the nanocomposites retained enough stiffness and strength under a biological state to provide effective support for bone tissue formation. The antibacterial activity was investigated against Gram-positive Staphylococcus aureus and Staphylococcus epidermidis as well as Gram-negative Pseudomonas aeruginosa and Escherichia coli microorganisms, and it rose sharply upon increasing GO concentration; systematically, the biocide effect was stronger versus Gram-positive bacteria. Cell viability data demonstrated that PPF/PEG-GO composites do not induce toxicity over human dermal fibroblasts. These novel materials show great potential to be applied in the bone tissue engineering field.
Biodegradable nanocomposites were prepared by adding ZnO nanoparticles to bacterial polyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) via solution casting technique. The morphology, ...thermal, mechanical, antibacterial, barrier, and migration properties of the nanocomposites were analyzed. The nanoparticles were uniformly dispersed within PHBV without the aid of coupling agents, and acted effectively as nucleating agents, raising the crystallization temperature and the level of crystallinity of the matrix while decreasing its crystallite size. A gradual rise in thermal stability was found with increasing ZnO loading, since the nanofillers hinder the diffusion of volatiles generated during the decomposition process. The nanocomposites displayed superior stiffness, strength, toughness, and glass transition temperature, whereas they displayed reduced water uptake and oxygen and water vapor permeability compared to the neat biopolymer, related to the strong matrix–nanofiller interfacial adhesion attained via hydrogen bonding interactions. At an optimal concentration of 4.0 wt % ZnO, the tensile strength and Young’s and storage moduli showed a maximum that coincided with the highest crystallinity and the best barrier properties. PHBV/ZnO films showed antibacterial activity against human pathogen bacteria, and the effect on Escherichia coli was stronger than on Staphylococcus aureus. The overall migration levels of the nanocomposites in both nonpolar and polar simulants dropped upon increasing nanoparticle content, and were well below the limits required by the current normative for food packaging materials. These sustainable nanomaterials with antimicrobial function are very promising to be used as containers for beverage and food products as well as for disposable applications like cutlery or overwrap films.
Novel poly(ether ether ketone) (PEEK) based nanocomposites have been fabricated via melt-blending by addition of a carboxylated polymer derivative covalently grafted onto the surface of ...hydroxyl-terminated ZnO nanoparticles. Their morphology, thermal, mechanical, tribological, and antibacterial properties have been analyzed and compared with those of composites reinforced with pristine ZnO. The Fourier transform infrared (FT-IR) spectra corroborate the success of the grafting reaction, showing the appearance of signals related to ester linkages. Microscopic observations demonstrate that the polymer grafting improves the nanoparticle dispersion within the matrix. A progressive rise in thermal stability and flame retardant ability is found with increasing ZnO concentration, with an exceptional increment in the maximum degradation rate temperature of 70 °C at 5.0 wt % loading. The crystallization and melting temperature of PEEK decrease upon incorporation of the grafted nanofillers, attributed to the restrictions on polymer chain mobility and crystal growth imposed by the strong ZnO-matrix interactions. Nanocomposites with polymer-grafted nanoparticles exhibit higher stiffness, strength, ductility, toughness and glass transition temperature whilst lower coefficient of friction and wear rate than the neat polymer and composites with bare ZnO. Further, they show superior antibacterial activity against both the Gram-negative Escherichia coli and the Gram-positive Staphylococcus aureus bacteria. The antimicrobial effect increases upon raising nanoparticle content, and is stronger on E. coli. The approach used in this work is a simple, scalable, and efficient method to improve the performance of PEEK/ZnO nanocomposites for use in biomedical applications such as trauma, orthopedics, and spinal implants.
Biocompatible and biodegradable nanocomposites comprising epoxidized soybean oil (ESO) as matrix, zinc oxide (ZnO) nanoparticles as reinforcements, and 4-dimethylaminopyridine (DMAP) as a catalyst ...have been successfully prepared via epoxidization of the double bonds of the vegetable oil, ultrasonication, and curing without the need for interfacial modifiers. Their morphology, water uptake, thermal, mechanical, barrier, tribological, and antibacterial properties have been investigated. FT-IR analysis revealed the existence of strong ESO–ZnO hydrogen-bonding interactions. The nanoparticles acted as mass transport barriers, hindering the diffusion of volatiles generated during the decomposition process and leading to higher thermal stability, and also reduced the water absorption and gas permeability of the bioresin. Significant improvements in the static and dynamic mechanical properties, such as storage and Young’s moduli, tensile strength, toughness, hardness, glass transition, and heat distortion temperature, were attained on reinforcement. A small drop in the nanocomposite stiffness and strength was found after exposure to several cycles of steam sterilization or to simulated body fluid (SBF) at physiological temperature. Extraordinary reductions in the coefficient of friction and wear rate were detected under both dry and SBF conditions, confirming the potential of these nanoparticles for improving the tribological performance of ESO. The nanocomposites displayed antimicrobial action against human pathogen bacteria with and without UV illumination, which increased progressively with the ZnO content. These sustainable, ecofriendly, and low-cost biomaterials are very promising for use in biomedical applications, like structural tissue engineering scaffolds.
► The fate of elements and properties of ashes were evaluated in BFB coal oxy-combustion plant. ► High abatement for SO2 and NOx (99.9%), Hg (92.5%) and remaining elements (99.9%) is obtained. ► Low ...retention for Cl is achieved (19%), being the main impurity for subsequent CO2 treatment. ► Most of the gaseous Hg occurs in the exhaust gas as Hg0 (81%).
The fate of trace elements and the properties of oxy-combustion residues were evaluated in a 90kWth bubbling fluidized bed (BFB) oxy-combustion pilot plant fed with coal and limestone (bed material). Sampling of solid streams (coal, limestone, bottom ash, cyclone fly ash, and bag-filter fly ash) and exhaust gas (SOx, NOx, CO2, CO, and Hg) was undertaken through 4h operating at 70% load, 70:30 CO2/O2 ratio of raw gas and 800–820°C in a single (without re-circulation) oxy-combustion test run. The retention of SO2 (98.2 %), NOx (99.9%), and Hg (92.5%) and remaining elements (99.9%) attained high efficiencies while low retention for Cl is achieved (19%). Speciation of gaseous Hg revealed that most of the gaseous Hg occurs in the exhaust gas as Hg0. The proportions of Cl and Hg in the exhaust gas may be considered of concern with respect to subsequent CO2-rich gas treatment and oxy-combustion cycles by partial re-circulation of exhaust gas. The high abatement capacity for most of elements (Hg, S, NH4+, F, Se, As, B, Se, Cd, and Sn) is mostly due to condensation in bag filters. The low gas temperature (45°C), and high-Ca content promotes condensation on fly ash collected in the bag filters. The Hg gaseous speciation and the enrichment in bag filters is indicative that most of the Hg retained is Hg2+, most probably as Hg-sulphate species. Calcite and lime are the main crystalline phases in bottom ash, quartz, illite, and calcite in cyclone fly ash and gypsum–bassanite in bag-filter fly ash. The dissolution of these species produces a moderate alkalinity (pH=10.7–11.1) in bottom ash and cyclone fly ash leachates and slight (pH=8) in bag-filter fly ash leachates. The leaching potential of most of elements in oxy-combustion residues is relatively low, falling in the range of non-hazardous materials according to Decision 2003/33/EC. Nevertheless, the high condensation of elements of environmental concern coupled with the use of a fuel rich in the aforementioned elements would increase the leachable potential, and consequently, may affect the disposal of this type of fly ash.
•The reduction reaction kinetics of highly loaded CuO-based have been determined.•A SCM with kinetic control for particles and pellets has been successfully applied.•The mixture of reducing gases has ...been analyzed in calcination/reduction stage.•Energy released during reduction and energy demand for calcination evolve close together.
In this work, the reduction reactions of highly loaded CuO-based materials with H2, CO and CH4, have been investigated. The oxygen transport capacity of the materials was barely affected (i.e. losses around 5%) along 100 reduction/oxidation cycles at 1123 K tested in TGA. The experimental results suggested that a shrinking core model (SCM) with chemical reaction control is able to predict the reduction conversion of highly loaded CuO-based materials in powder and pellet form, and the kinetic parameters were accordingly determined to this model. The activation energy values obtained for the materials supported over Al2O3 and MgAl2O4 are in the range of 10 kJ mol−1 for H2, 25 kJ mol−1 for CO and 60 kJ mol−1 for CH4, in agreement with results published in the literature, indicating that using Al2O3 or MgAl2O4 as support has not a significant effect on the reactivity. It has been found that internal diffusion plays a role for the highly loaded CuO-based in pellet form when supported over MgAl2O4 and when using CO and CH4 as reducing agents. Mixtures of reducing gases have been also tested in the TGA for a pellet using Al2O3 as support and the experimental results have been successfully fitted using the kinetic parameters previously determined. Finally, a simplified energy balance for the reactions involved in the reduction/calcination stage of the Ca/Cu process has been performed to determine operational conditions in which the reaction fronts for both reactions proceed together in the reactor. The results indicate that the materials tested present suitable reaction kinetics to sustain the reduction/calcination stage.
A novel biodegradable poly(glycolic acid-co-propylene fumarate) (PGA-co-PPF) copolymer has been synthesized via ring-opening polymerization. Graphene oxide (GO) and hydroxyapatite nanorods have been ...incorporated into PGA-co-PPF through electrospinning to yield hybrid nanocomposite fibers, and their morphology, water uptake, biodegradability, cytotoxicity, and mechanical, thermal and antibacterial properties have been analyzed. The addition of GO improved the dispersion of the HA nanorods within the matrix, and led to the formation of thinner fibers. The simultaneous incorporation of both nanofillers significantly increased the water absorption, biodegradation rate and protein adsorption capability of PGA-co-PPF. The hybrids induced higher osteoblast cell vitality and alkaline phosphatase activity than the neat copolymer and binary nanocomposites with either HA or GO, and showed higher biocidal activity against Gram-positive S. aureus and Gram-negative E. coli bacteria. Furthermore, experimental results revealed a synergistic effect of the nanofillers on improving the copolymer biocompatibility, thermal stability, stiffness, strength and toughness, and the nanocomposite with 20 wt% HA and 5 wt% GO exhibited the best combination of properties. The development of multifunctional polymer nanocomposite fibers with good biodegradability, very low toxicity, high tensile modulus and strong bactericidal activity opens up new perspectives for bone tissue engineering applications.
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