Due to its slow degradation rate, polycaprolactone (PCL) is frequently used in biomedical applications. This study deals with the development of antibacterial nanofibers based on PCL and halloysite ...nanotubes (HNTs). Thanks to a combination with HNTs, the prepared nanofibers can be used as low-cost nanocontainers for the encapsulation of a wide variety of substances, including drugs, enzymes, and DNA. In our work, HNTs were used as a nanocarrier for erythromycin (ERY) as a model antibacterial active compound with a wide range of antibacterial activity. Nanofibers based on PCL and HNT/ERY were prepared by electrospinning. The antibacterial activity was evaluated as a sterile zone of inhibition around the PCL nanofibers containing 7.0 wt.% HNT/ERY. The morphology was observed with SEM and TEM. The efficiency of HNT/ERY loading was evaluated with thermogravimetric analysis. It was found that the nanofibers exhibited outstanding antibacterial properties and inhibited both Gram- (
) and Gram+ (
) bacteria. Moreover, a significant enhancement of mechanical properties was achieved. The potential uses of antibacterial, environmentally friendly, nontoxic, biodegradable PCL/HNT/ERY nanofiber materials are mainly in tissue engineering, wound healing, the prevention of bacterial infections, and other biomedical applications.
Conductive polymer composites (CPC) from renewable resources exhibit many interesting characteristics due to their biodegradability and conductivity changes under mechanical, thermal, chemical, or ...electrical stress. This study is focused on investigating the physical properties of electroconductive thermoplastic starch (TPS)–based composites and changes in electroconductive paths during cyclic deformation. TPS–based composites filled with various carbon black (CB) contents were prepared through melt processing. The electrical conductivity and physicochemical properties of TPS–CB composites, including mechanical properties and rheological behavior, were evaluated. With increasing CB content, the tensile strength and Young’s modulus were found to increase substantially. We found a percolation threshold for the CB loading of approximately 5.5 wt% based on the rheology and electrical conductivity. To observe the changing structure of the conductive CB paths during cyclic deformation, both the electrical conductivity and mechanical properties were recorded in parallel using online measurements. Moreover, the instant electrical conductivity measured online during mechanical deformation of the materials was taken as the parameter indirectly describing the structure of the conductive CB network. The electrical conductivity was found to increase during five runs of repeated cyclic mechanical deformations to constant deformation below strain at break, indicating good recovery of conductive paths and their new formation.
This paper is focused on the preparation of novel hybrid polymer composite materials for 3D filaments. As the reinforcing filler, expanded graphite, carbon fibers, and combinations thereof were used ...in various ratios up to 10%. The mechanical and thermal properties of virgin and recycled polyethylene phthalate glycol-modified (PETG) composite materials were determined. Almost all prepared composite materials were suitable for 3D printing and they have enhanced mechanical properties compared to the neat PETG matrices. Addition of the fillers to both polymer matrices has an only slight effect on the thermal stability, but the addition of carbon fibers significantly reduced the thermal expansion coefficient. The composites from cheaper recycled PETG have comparable properties to virgin PETG composites, which is of economic and ecological importance. New and cheaper materials can help expand 3D printing to manufacturing plants and the use of 3D printers for special applications.
The main goal of the paper was to numerically analyse the risk of overheating of the Energy Activated External Thermal Insulation Composite System (En-ActivETICS) as an example of Building Integrated ...Photovoltaics (BIPV). The analyses were conducted with the coupled power flow method (thermal and electrical) for 20 European cities. All locations were analysed considering the local climate in the context of building performance simulation as well as electricity production. The obtained results allowed for the determination of the risk of overheating, which can influence system durability, accelerated thermal ageing, and overall performance. It was revealed that the risk of overheating above 80 °C is possible in almost all locations; however, the intensity considerably differs between southern and northern Europe. The effect of latent heat storage for better thermal stabilization and overall performance was determined numerically for all locations. Finally, the improved solution with a phase change material (PCM) layer beside the PV panel was proposed individually for specific climatic zones, considering the required heat capacity. The maximum panel temperature for improved En-ActivETICS does not exceed 85 °C for any location.
Persistent microbial contamination of medical implant surfaces is becoming a serious threat to public health. This is principally due to antibiotic-resistant bacterial strains and the formation of ...bacterial biofilms. The development of novel antibacterial materials that will effectively fight both Gram-positive and Gram-negative bacteria and prevent biofilm formation represents a big challenge for researchers in the last few decades. In the present work, we report an antibacterial hydrophobic carbon quantum dots/polyurethane nanocomposite (hCQD-PU), with enhanced antibacterial properties induced by pre-treatment with gamma-irradiation. Hydrophobic quantum dots (hCQDs), which are capable of generating reactive oxygen species (ROS) upon irradiation with low-power blue light (470 nm), have been integrated into the polyurethane (PU) polymer matrix to form a photoactive nanocomposite. To modify its physical and chemical properties and improve its antibacterial efficacy, various doses of gamma irradiation (1, 10, and 200 kGy) in the air environment were applied to the formed nanocomposite. Gamma-irradiation pre-treatment significantly influenced the rise in ROS production, therefore, the prooxidative activity under the blue-light illumination of hCQD-PU was also significantly improved. The best antibacterial activity was demonstrated by the hCQD-PU nanocomposite irradiated with a dose of 200 kGy, with the complete eradication of Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) bacteria after 15 min of exposure to the blue lamp.
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•Gamma-irradiation of hydrophobic carbon quantum dots/polyurethane nanocomposites.•Increase of the production of reactive oxygen species after the gamma-irradiation.•Visible-light triggered fast and efficient antibacterial activity.•Low toxicity of gamma-irradiated nanocomposites.•Excellent candidates for various antibacterial surfaces and bio-interfaces.
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•A new procedure for the preparation of PCM microcapsules was developed.•The synthesis of microcapsules can be applied at semi-industrial scale.•Microcapsules decrease melting and ...crystallization temperature of HDPE.•Microcapsules decrease the complex viscosity of blends.
A modified in situ polymerization microencapsulation procedure for the preparation of microcapsules with paraffin wax cores (43wt.%) and melamine–formaldehyde resin shells having a uniform size distribution and a spherical shape with average diameters of approximately 15μm was developed. The high-density polyethylene/microcapsule blends were prepared via two routes. In the first case, the dry high-density polyethylene powder covered by microcapsules was simply hot pressed, whereas, in the second case, the dry high density polyethylene/capsule powder was first blended in the molten state to obtain better homogeneity before hot pressing. It was observed that both systems behave qualitatively the same with comparable mechanical properties and thermal behavior.
The thermal stability of high-density polyethylene/microcapsule blends characterized by thermogravimetry is significantly lower than that of neat high-density polyethylene. The selected characteristic temperatures of degradation decreased by more than 200°C compared with the related temperatures for neat high-density polyethylene.
An analysis based on Differential Scanning Calorimetry revealed separated melting and crystallization behavior of wax within the capsules and high density polyethylene in the blends. The enthalpies of melting and crystallization are proportional to the amount of individual components in the material. The capsules have a strong plasticizing effect on the high density polyethylene, resulting in a significant decrease in the melting and crystallization temperatures. The plasticizing effect was also confirmed by measurements of the tensile mechanical properties and rheological behavior.
Industrialization today leads to a significant increase in the environmental pollution, with number of phenols, pesticides, paints, solvents and other organic pollutants with potentially carcinogenic ...effect in natural resources. Investigation of some new semiconductor materials and their photocatalytic properties for removal of pollutants is a challenging work. However, limited usage of photoactive materials still requires the testing of new materials with photoactive properties. The current work introduces the swift and easy approach for synthesis of (metal–free) N–doped carbon quantum dots in water using microwave reactor. Synthesis was performed from glucose water solution by heating in microwave reactor for only 1 min, at low temperature and applied microwave power. The synthesized N–doped carbon quantum dots show remarkable photocatalytic activity for removal of toxic organic dye (Rose Bengal) under visible light irradiation. Almost 93% of the dye degradation is achieved after only 30 min of radiation. The uninspected result, that the pH of the medium has a significant effect on the performance of the synthesized material in the presence of organic dye, indicates that dots show dual behavior. In the neutral and basic conditions, they have the ability to degrade organic dye, whereas, by shifting the medium pH into acidic medium, they form a stable conjugate with Rose Bengal.
Material extrusion (MEX) of thermoplastic filaments represents one of the most widely adopted additive manufacturing (AM) technologies. Unlike vat photopolymerization and powder-bed fusion methods ...that require high energy sources such as UV light and lasers, this fabrication method can be adapted for the fabrication of ceramics by using ceramic loaded filaments as feedstock, yet still employing relatively cheap equipment meant for polymeric materials with little adaptation of the process parameters; this potentially enables a broader diffusion of AM ceramic components. In this work, composite filaments with various weight fractions (60 – 80 wt%) of BaTiO3 were fabricated and characterized by electron microscopy, compressive mechanical testing, rheometry and thermogravimetric analysis to ensure a smooth and reliable printing process. After optimizing the printing parameters, the dense and porous printed samples were carefully debinded and sintered to obtain dense (∼ 92 %) and defect-free ceramic bodies. The sintered samples were characterized for phase development, microstructure, and pore size distribution. Careful observations reveal a particular range of pore size (0.1 – 5 µm), which originates from the binder burn out process. The dielectric and ferroelectric properties of the fabricated samples were in good agreement with those reported in previous literature. This work provides a foundation for rapid prototyping of functional electro ceramics into reliable products with desired functional properties.
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•Filaments with up to 78 wt% of BaTiO3 printable with nozzles down to 0.3 mm.•No chemical debinding required for the porous structures.•Short thermal debinding time of ∼13 hours.•Relative density of ∼92 % and dielectric and ferroelectric properties in good agreement with previous literature.
•Electrospinning is a scaffold fabrication method.•Integrating other materials such as metals nanoparticles with polymers is emerging as a route to new composites materials.•Electrospun ...polymer-nanoparticles composites are a new frontier in biomedicine.•We summarise advances in electrospun tissue engineering and wound dressing platforms.•Polymer-titanium dioxide nanocomposites is discussed here.
Electrospinning is widely used to fabricate nanoscale fibers from natural and synthetic polymers. Electrospun fibers have potential application in tissue engineering as well as in the design of catalysts, batteries, electronic sensors, packages, filtration membranes, medical implants, wound dressings, and medical fabrics, and drug delivery systems. Fibers offer a porous structure with a high surface area to volume ratio, which is a highly desired property in various applications. Integrating other materials such as metals nanoparticles or ceramics in electrospun fibers is emerging as a route to new nanoscale composites materials with enhanced functional properties. Incorporating nanoparticles on or within the nanofibrous scaffold impart functional properties with implication for catalysis, optoelectronics, and biomedicine. Indeed, these electrospun polymer-nanoparticles composites are a new frontier in biomedicine, where their relevance to tissue engineering, wound dressing, drug delivery is emerging. Here, we summarise advances in electrospun tissue engineering and wound dressing platforms developed from polymer-titanium dioxide nanocomposites.
This study serves to combine two approaches into one single step, to achieve a significant improvement of the light-induced actuation capabilities. Graphene oxide (GO) is an inert material, from the ...electrical and thermal conductivity point of view, and is incompatible with the usually-used poly(dimethylsiloxane) (PDMS) matrix. During surface-modification by surface-initiated atom transfer radical polymerization, the GO was transformed into a conducting and compatible material with the PDMS showing enormous light-induced actuation capability. The GO surface-modification with poly(2-(trimethylsilyloxy)ethyl methacrylate) (PHEMATMS) chains was confirmed by transmission electron microscopy and thermogravimetric analysis, with an on-line monitoring of gasses using FTIR. The improved compatibility was elucidated using contact angle and dielectric properties measurements. The PHEMATMS shell was investigated using gel permeation chromatography and nuclear magnetic resonance. The improved electric conductivity was measured using the four-point probe method and by Raman spectroscopy. The very important mechanical properties were elucidated using dynamic mechanical analysis, and with the help of thermo-mechanic analysis for the light-induced actuation. The excellent actuation capabilities observed, with changes in the length of around 0.8% at 10% pre-strain, are very promising from the point of view of applications.
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