A polymeric nanocomposite system for potential adhesive applications in restorative dentistry

This article presents and discusses the preliminary results obtained as a continuation of a work aiming to contribute to the effort of exploring the potential of certain types of polymer nanocomposites to be successful candidates in new fields such as dental restoration. An epoxy-functional silicate-/Zr-based polymeric nanocomposite material system containing phosphorus was obtained via a sol–gel method, and applied to bring about a bonding between bovine teeth and feldspathic ceramic discs with or without the use of visible light (VL)-curing process. Infrared spectroscopy was employed to show the presence of phosphorus within the structure. Mechanical tests were performed to determine the shear-bond strength of the nanocomposite adhesive system developed. An approximate shear-bond strength value of 0.4 MPa was obtained for both VL-cured and uncured systems. Though this value was lower than that of commercially available material systems, it was promisingly comparable to them. Another significant finding was that the material system developed within the study might potentially eliminate the use of curing process. Also, it was demonstrated that the general problem of ‘shrinkage-upon-polymerization’ could be overcome by use of a polymeric nanocomposite adhesive material system of this type. Overall results indicated that this polymeric nanocomposite system could indeed be potentially considered as an adhesive alternative in prospective dental restoration applications.     

Stress wave propagation in a through-thickness functionally graded adhesive layer

In this study, an improved mathematical model is presented to investigate the stress wave propagation in two circular cylinders bonded with a functionally graded adhesive layer. In the proposed model, the spatial derivatives of mechanical properties are included in the governing equations of the wave propagation. Also, the finite-difference method was used for the solution of the governing equations and boundary conditions. The Mori-Tanaka homogenization scheme was employed to evaluate the through-thickness mechanical properties of the adhesive layer. The effects of the spatial derivatives of the local mechanical properties and the through-thickness material composition variation in the adhesive layer were examined in detail. The presence of the material spatial derivatives in the governing equations mitigated the stress and displacement levels as well as axial and radial wave speeds.     

Heat pump drying of grape pomace: Performance and product quality analysis

Abstract

Grape is one of the most popular fruits and various types of grape have been cultivated by more than 100 countries around the World. The wine and juice industry produces large quantities of by-product, called grape pomace (GP) as an industrial waste and it consists of skins, seeds, and stems. Various processes such as separation, pressing, drying, and milling are applied to benefit from its health effects. In this study, the seeded black GP Kalecik karas? (Vitis vinifera) was dried in an assisted closed cycle heat pump dryer (HPD) designed for high-moisture products to investigate the drying behaviors of GP. The effects of drying air temperature on bioactive properties and the drying characteristics of GP, and performance of system have discussed. Experiments were carried out at two different temperatures (45 and 50°C) and air velocity of 1.0 m/s. It was seen that increasing temperature decreased the drying time, coefficient of performance of whole system (COP_ws), and specific energy consumption (SEC). The average values of COP_ws for temperatures 45°C and 50°C were calculated as 3.28 and 3.10, respectively. The drying efficiencies (DE) at drying air temperature of 45°C and 50°C ranged from 2 to 12% and from 2 to 15%, respectively. Additionally, result of analysis has indicated that using a HPD at lower temperatures increases performance of system despite of higher energy input. Bioactive properties of dried samples at drying air temperature of 45°C are better than 50°C. The results show that drying the GP at low temperature is more suitable for product quality. For this reason, heat pump may be preferred. It shows that this drying system with higher capacities in the future can be recommended as an alternative technique in terms of energy usage, drying time, and performance of system.     

Poly(l-lactide) initiated by silver N-heterocyclic carbene complexes: synthesis, characterization and properties

Poly(l-lactide) (PLLA) was successfully synthesized by ring-opening polymerization (ROP) in bulk using silver N-heterocyclic carbene (Ag–NHC) complex. The effect of reaction time, temperature and monomer/initiator ratio on polymerization process were determined. The optimum conditions were found as 130 °C, 4 h and M/I molar ratio of about 100. The polymers were characterized by FTIR, ¹H-NMR, GPC and TG. High-molecular-weight PLLA (M _w = 3.78 × 10⁴, M _n = 1.91 × 10⁴, PDI = 1.97) was synthesized by the ROP of l-lactide (LLA) with bis-(N-methyl N′-dodecylimidazole) silver(I) di-bromo argentate (1a) in bulk. The effect of different N-substituted ligand groups on the polymerization was studied. The antimicrobial activity of the synthesized polymers were investigated by using minimum inhibitory concentration test against gram positive (Staphylococcus aureus) and gram negative (Escherichia coli and Pseudomonas aeruginosa). It was observed that the synthesized polymers displayed moderate antimicrobial activity.     

Fabrication of Gentamicin Sulfate-Loaded 3D-Printed Polyvinyl Alcohol/Sodium Alginate/Gelatin-Methacryloyl Hybrid Scaffolds for Skin Tissue Replacement

3D-printed scaffolds can better mimic the function of human skin, both biologically and mechanically. Within the scope of this study, the effect of the addition of different amounts (10, 15, 20 mg) of gentamicin sulfate (GS) to a 10 mL solution of natural and synthetic polymers is investigated. Sodium alginate (SA), gelatin-methacryloyl (GelMA), and polyvinyl alcohol (PVA) are chosen as bioactive materials. The surface morphology and pore structures are visualized by scanning electron microscopy (SEM). According to the results, it is observed that the pore sizes of all scaffolds are smaller than 270 µm, the lowest value (130 µm) is obtained in the scaffold loaded with 15 mg GS, and it also has the highest tensile strength value (12.5 ± 7.6 MPa). Similarly, it is observed that the tensile strength (9.7 ± 4.5 MPa) is high in scaffold loaded with 20 mg GS. The biocompatibility test is performed with fibroblast cells, and the results show that the scaffolds are biocompatible with cells. The antibacterial test is carried out against the S.aureous and E. coli and the results indicate that all GS-loaded scaffolds demonstrate antibacterial activity.     

Ultrasound- and Microwave-Assisted Extractions Facilitate Oil Recovery from Gilthead Seabream (Sparus aurata) By-Products and Enhance Fish Oil Quality Parameters

This research aimed to analyze ultrasound (UAE) and microwave-assisted extraction (MAE) as novel technologies for utilizing gilthead seabream (Sparus aurata) by-products to produce high-quality fish oil for human consumption. The impacts of extraction parameters, namely, temperature, time, solvent-to-solid ratio, and their interactions on the extraction yield, are investigated using response surface methodology (RSM), and a central composite rotatable design. The optimized conditions are 15.47 mL g⁻¹ of solvent-to-solid ratio, 38 min, and 42 °C for UAE and 15.84 mL g⁻¹ of solvent-to-solid ratio, 18 min, and 40 °C for MAE. Under optimal conditions, the maximum extraction yields are 38.40 and 36.70% (g/g) for UAE and MAE, respectively. Both UAE and MAE have significantly higher mass transfer rates (61.70 and 121.58 g h⁻¹, respectively) than Soxhlet extraction (10.78 g h⁻¹). The fatty acid composition, physicochemical, and oxidation analyses of fish oils confirm the suitability of both UAE and MAE for the recovery of high-quality oils from fish processing by-products. The valorized oils mainly include unsaturated fatty acids (≈75%) and are rich in oleic acid. Furthermore, scanning electron microscopy analysis reveals that the key driving force for fast oil extraction is the structural degradation of fish by-products caused by ultrasound and microwave. Practical Applications: Due to environmental and economic viewpoints, the validation of fish oil from fish industry by-products has become a popular research topic recently. Alternative recovery techniques such as ultrasound- (UAE) and microwave-assisted extraction (MAE) protocols may have additional benefits in producing functional oils. Interactive effects of process parameters determine the success of the extraction technique; therefore optimization is a critical approach when applying the extraction protocols. This study shows that UAE and MAE techniques significantly enhanced oil extraction rate from gilthead seabream (Sparus aurota) by-products at lower temperatures and by using lower amounts of solvent. UVA and MAE increase oxidative stability and do not change the fatty acid composition. Hence, the by-product of the gilthead seabream can be a sustainable and food-grade fish oil source and UAE and MAE can be a good alternative to the conventional (Soxhlet) extraction by providing high yield and quality oil.     

The influence of system scale on impinging jet sediment erosion: Observed using novel and standard measurement techniques

Jet impingement as a method for eroding particulate beds and maintaining sediment in suspension is an important process for a host of industries, particularly in nuclear waste processing, where such systems to disperse and mix particulate beds have a number of advantages over other approaches. Existing work has utilised fairly rudimentary techniques for the measurement of erosion depths and here we demonstrate a new technique for measuring both static and dynamic erosion of cohesionless particulates under an impinging jet, using ultrasonic Doppler velocimetry. This approach is tested on both quartz sands and on a range of Mg(OH)₂ particulates that are key simulants for nuclear waste facilities, such as the Highly Active Storage Tanks at Sellafield, U.K. A critical jet height was found to exist that balanced the impingement velocities and total entrained jet volume to maximise erosion. The effect of system scale was also considered by normalising steady-state crater depths and sizes, with erosion being enhanced in the small scale, possibly due to increased turbulent recirculation. Additionally, velocity profiles and acoustic backscatter were used to determine both steady-state crater profiles and kinetic changes in bed-depths with time, and highlighted important differences between static and dynamic measurements of erosion depth.     

Removal of reactive dyes from wastewater by acrylate polymer beads bearing amino groups: isotherm and kinetic studies

The aim of this study was to prepare a novel resin for the removal of reactive dyes from aqueous media. To prepare the resin, poly(2‐hydroxyethyl methacrylate/ethylene glycol dimethacrylate) beads were grafted with poly(glycidyl methacrylate) by surface‐initiated atom transfer radical polymerisation. Epoxy groups of the grafted polymer were modified with tris(2‐aminoethyl)amine ligand. The modified resin was characterised by swelling studies, FT‐IR and SEM. Three different reactive dyes were selected (CI Reactive Brown 10, CI Reactive Red 120 and CI Reactive Green 5) and used in the removal studies. The effects of pH, temperature, ionic strength and initial dye concentration on the adsorption capacity of the resin were investigated. The adsorption capacity of the resin for Reactive Brown 10, Reactive Red 120 and Reactive Green 5 was 0.029 ± 0.010, 0.032 ± 0.0019 and 0.042 ± 0.0013 mmol/g resin (34.1 ± 1.2, 47.6 ± 2.3 and 69.3 ± 1.7 mg/g resin) respectively. The equilibrium adsorption data were analysed by Langmuir, Dubinin–Radushkevich, Freundlich and Temkin isotherm models. A good fit was found between the Langmuir isotherm and data for the three dyes on resin. The adsorption kinetic data were modelled using pseudo‐first‐order, pseudo‐second‐order and intraparticle diffusion kinetic equations. It was found that the pseudo‐second‐order equation could describe the adsorption kinetics. The results indicated that the modified resin is an attractive alternative for removing reactive dyes from wastewater.     

PHOTOCATALYTIC OXIDATION OF ALDEHYDES/PCE USING POROUS ANATASE TITANIA AND VISIBLE-LIGHT-RESPONSIVE BROOKITE TITANIA

We have synthesized an annealed porous aerogel titania (LUAG2), which demonstrates a very high photocatalytic activity for aldehydes and perchloroethylene (PCE) photocatalytic oxidation (PCO) in gas phase under blacklight and fluorescent light irradiation. LUAG2 has a BET surface area of 237 m²/g and a porosity of 0.31 (volume fraction). X-ray diffraction (XRD) analysis shows LUAG2 is nearly pure anatase. It has improved the destruction of PCE and aldehydes as a group by 10–34% with black light compared to Degussa P-25. The optimum water vapor to butyraldehyde molar ratio is around 1/3. LUAG2 also shows better mineralization to CO₂ than Degussa P-25 TiO₂ does. Under irradiation of a 4 W fluorescent lamp LUAG2 gives a consistently higher conversion than that of Degussa P-25. The highly active photocatalyst indicates potential applications in indoor and outdoor environmental pollution control. A visible-light-responsive TiO₂, NTB 200, is also investigated for comparison purposes.     

Effect of bio‐oil and epoxidized linseed oil on physical,mechanical, and biological properties of treated wood

In this article, the effects of bio‐oil and epoxidized linseed oil (ELO) on water absorption, tangential swelling, decay and insect resistance, thermo‐gravimetric analysis, and mechanical properties of treated wood samples were studied. The bio‐oil used in this article was by‐product of ThermoWood thermal modification process. Linseed oil and hydrogen peroxide were used to prepare ELO. The results indicated that the samples treated with bio‐oil had lower water absorption than that of the control group. The second treatment with ELO significantly reduced further the water absorption. The decay resistance of treated wood samples with 20% of bio‐oil against brown (Coniophora puteana) and white rot (Trametes versicolor) fungi was very high. According to the insect test results, increasing bio‐oil concentration from 10% to 20% significantly decreased surviving rate of Hylotrupes bajulus. Thermo‐gravimetric analysis showed that all treated samples had higher initial deterioration temperature than that of the control group. Regarding the wood strength, the impregnated bio‐oil generally reduced the mechanical properties of wood except modulus of elasticity (MOE). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1562–1569, 2013