The paper aims to evaluate the gel time and exotherm temperature properties of the curing of unsaturated polyester resin at various amounts of Methyl ethyl ketone peroxide, cobalt octoate and porcelain powder. The gel time of samples are determined using the simple method, while the exotherm temperature are evaluated using the thermocouple. The variation of these properties is discussed theoretically and experimentally.
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The most significant disadvantage of cold cured poly (methyl methacrylate) – PMMA is its poor mechanical properties, mainly in flexure. The aim of this work is to explore the modulus and flexural strength of modified cold cured PMMA modified with low TiO2 addition, which can also have antibacterial properties. Commercial cold cured PMMA resin, consisting of powder and liquid components, were modified by adding 0.05 %, 0.2 %, and 1.5 wt. % 20 nm hydrophobic TiO2. The specimen`s flexural modulus and strength were tested, while heat properties were determined with DSC analysis. SEM and EDX were used to study fracture surfaces of tested specimens. In all modified specimens, an increased flexural modulus and flexural strength were recorded. In all specimens, the appearance of agglomerates was noted. Glass transition temperatures also increased, as the result of the appearance of polymer chains with reduced mobility around nanoparticles. 0.2 % of 20 nm TiO2 nanoparticle content proved to be the most efficient in increasing flexural modulus and strength.
With the development of unmanned aerial vehicle (UAV) systems for a multitude of real-time applications, 3D printing technologies have been developed to make thermoplastic structures by fusing filament Fused Deposition Modeling (FDM) or Fused Filament Fabrication (FFF). However, we consider that the realization of new technologies of experimental models / technological demonstrators / prototypes becomes profitable by using 3D printing technologies. The main aim of the paper is to highlight how the use of three types of materials, which are processed differently, influences the Von Mises stresses of the payload used for a UAV, with the mission of photographing and filming from high altitude.
The aim of this paper is to obtain two types of bio-based membranes by electrospinning process: one based on polylactic acid (PLA), and PLA/polyhydroxybutyrate (PHB), and the second by coating the PLA/PHB membrane with chitosan (CS) and CS/activated coal (AC), respectively for removal of micropollutants from aqueous water. The designed bio-based electrospun membranes were analyzed through scanning electron microscopy (SEM), attenuated total reflectance (ATR) – Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), the removal of solid suspension and Pb (II) from aqueous water. The quality of filtrates was evaluated by physical-chemical methods, while the retaining of Pb (II) from wastewaters was reported.
In the present work, the effect of the addition of different types of carbon nano structures on the mechanical, thermomechanical and thermal properties of a radial structure of styrene-butadiene-styrene (SBSR) copolymer matrix is reported. Different carbon nanostructures were used as nano-rein-forcements: expanded graphite (XG), graphene oxide (GO), reduced graphene oxide (RGO) and exfo-liated graphene (EG). These carbon structures present various functional groups, such as carbonyl, epoxy, and others, which are the responsible for the interaction between the polymer matrix and the nano particles. The compatibility induced between the nanomaterials and the elastomeric matrix fa-vors the stable dispersion of the nanocomposites during their obtention process. For instance, the ad-dition of GO increased in 10 and 16% the tensile strength and storage modulus of the nanocomposites. The fracture surface patterns in the nanocomposites after the tensile test was observed by scanning electron microscopy. Also, the dynamic mechanical analysis (DMA) and thermal characterization showed differences in the viscoelastic behavior of the reinforced nanocomposites with different carbon nanomaterials.
Membrane research has managed to reach ever greater heights. The optimization of membrane processes is of common interest to industry, research and the domestic environment. Nanomaterials have been progressively researched in the membrane sector within the last decade, contributing in particular to their beneficial properties for the prevention of membrane fouling. This research investigates the effect of two shapes of ZnO nanomaterials, respectively nanoparticles and nanowires, on the properties of ultrafiltration membranes composed of 25 wt.% polysulfone. The method of membrane manufacturing is phase inversion, the immersion precipitation technique, and the procedure of nanomaterial incorporation into the polymeric matrix is known as blending. The results demonstrated the positive influence of nanomaterials on the performance of membranes, regardless of their shape, compared to the control membrane. In terms of permeability, the membrane with addition of ZnO nanoparticles showed an increase of 207.19 %, while the membrane with addition of zinc oxide nanowires recorded an increase of 89.16%.
The aim of this paper was to present the synthesis, characterization and application of the Fe3O4 - chitosan composite as potential adsorbent for removing lead ions from industrial wastewater. The nanocomposite nanomaterial was characterized by XRD and SEM analyzes. The influence of some parameters (pH of wastewater, lead ions concentration and dose of Fe3O4 - chitosan absorbent) upon the efficiency of wastewater treatment were investigated. The Pb (II) ions concentrations in wastewater were 0.5, 1, 1.5 and 2 mg/L. The amounts of Fe3O4 - chitosan nanocomposite adsorbent tested were 0.05, 0.1 and 0.2 g. In some experimental conditions, Fe3O4 - chitosan nanocomposite adsorbent leaded to obtaining of 100% wastewater treatment efficiency.
The article presents results regarding the use of the melt flow index method (MFIM) in estimating the rheological properties of polylactic acid (PLA) and PLA-based materials, as tool in the selection of the operating conditions at their shaping into filaments and for 3D printing with thus obtained filaments. Based on the MFIM, the molecular weight of various PLA grade commonly used in melt processing techniques, including printing, were qualitatively compared. It was found that PLA for printing has the lowest molecular weight as compared with the PLA melt processed through injection, extrusion, thermoforming. It has been also shown that the MFIM can be used to verify the efficiency of drying, pre-treatment always needed to be done, before filaments obtaining and/or printing, especially in case of renewable polyesters. By simulating the printing at the indexer, via depositing successive layers, one over the other, it was possible to estimate the optimal flow conditions that ensure a good adhesion between the deposited layers. The estimation of the condition which ensure the needed adhesion between the deposited layers with the help of the MFIM was verified with good results on a grade of high loaded PLA achieved according to an original formulation.
Composites of Silver nanoparticles/chitosan were obtained in aqueous solution, in-one step and eco-friendly synthesis, under ambiental conditions, using gamma irradiation. The radiochemical synthesis enabled obtaining of controlled size, monodisperse and high stability Silver nanoparticles. The obtained composites presented UV-Vis surface plasmon resonance comprised between 406-414 nm, depending on composition of the reactant system, spherical shape and narrow particle size distributions, with mean dimensions between 3-55 nm, and good antibacterial properties proven against Staphylococcus aureus and Escherichia coli. The influence of the Silver ions/chitosan ratio and of the pH of the initial solution on the final Ag Np properties is also discussed.
The main purpose of our study was to demonstrate the antioxidant properties of novel propolis nano-formulation, incorporated in spherical chitosan nanoparticles. The electrochemical methods (cyclic voltammetry and differential pulse voltammetry) were successfully applied to propolis extract and nanopropolis formulation, confirming that the content in phenolic acids and flavonoids is responsible for the antioxidant activity of propolis. The quantitative and qualitative results are also supported by high performance liquid chromatography (HPLC) and ultraviolet-visible (UV-Vis) spectroscopy.