Browse Articles

The aim of this study was to obtain an edible film polymer matrix naturally extracted from tubers of Helianthus tuberosus L and biologically active components extracted from the roasted seeds of Vitis vinifera, in order to protect the active components from oxidation reactions during food conservation. The film was prepared by filling technique. It was evaluated the antioxidant activity of the film by means of DPPH (98.7%) technique, solubility water solubility (20.4%) and Isothermal sorption of water by GAB (Guggenheim, Anderson, de Boer) technique resulting a value of water activity of 0.167 and a value monolayer of 0.026 g water/g film. Through these values the resulting film ensure a sound management of the evolution of biological systems from the point of view of their complexity, especially food whose degradation can impact on their safety.

The main goal of this study was to modify halloysite with polyethylene glycol methacrylate and polyethylene glycol dimethacrylate in order to realize some pH sensitive controlled drug delivery systems. The obtained samples were characterized by spectral techniques (FTIR, XPS) and thermal techniques (TGA, DSC). There was also studied the influence of clay type and initial clay amount onto the drug adsorption process within halloysite. The hydrocortisone release profile was also investigated in simulated gastric fluid and simulated intestinal fluid.

At global scale, the trend of developing new thermoresistant polymeric structures, obtained from a mixture of dynamically cured elastomer/plastomer, and compatibility and curing agents, broadens their area of application and leads to greening of their processing technology and qualitative performance. Through dynamic curing and compatibilization, the elastomeric particles disperse more readily in the mixture thus making it possible to develop new innovative materials and techniques. Polymer structures were obtained by extrusion granulation technology, tested physico-mechanically (hardness, elasticity, tensile strength) according to current standards and morphologically by electron microscopy (SEM).

The aim of this work is to examine the role of alloying elements (Cu, Mg, Zn) in the complex reactions occurring in the heterogeneous system Al-Cu-Mg-Zn/K2TiF6/KBF4 at high temperatures. The paper presents theoretical and experimental studies to obtain aluminothermic reactions of composite AA7xxx/TiB2, putting into evidence the thermodynamic calculations and X-ray diffraction resulting compounds.

Batch adsorption of 4-nitrophenol (4-NP) from aqueous solutions on some non-ionic porous copolymers based on the styrene and divinylbenzene was investigated. The adsorption studies were performed as a function of various parameters: contact time, initial concentration of 4-NP solution and adsorbent/adsorbate ratio. Equilibrium and kinetics studies were investigated. Also, from the adsorption data the specific surface area of the polymeric adsorbents has been determined. The results showed that the porous beads prepared in presence of porogen mixture (toluene:gasoline) could have potential applications in the treatment of environmental pollution caused by 4-NP.

The poly(betaines) have been still intensively studied due to them biomedical potential. In the present work, two poly(carboxybetaines) derived from poly(4-vinylpyridine) P4VP that have methylene (P4VPB-1) or ethylene (P4VPB-2) spacer between N+ and COO- groups were investigated in order to evaluate its physico-chemical properties in aqueous salted solutions with NaCl or CaCl2. The values of refractive index increment dn/dc, weight-average molecular weight Mw, hydrodynamic radius Rh, and particle size distribution depend on the solvent type and balance between molecular forces as refractometric and laser light scattering measurements showed.

Aeronautic industry is on the trend of development and more comforts are being incorporated in the aircrafts. On the other hand it is necessary to achieve stringent demand of fuel economy and high performance at low cost. To achieve high fuel economy the aeronautics manufacturers are induced to reduce weight in the possible fields. Light weight composite materials like carbon fiber for the impeller of aerodynamic compressors have been used to achieve the requirements of the aeronautics industry. The paper is focused on the FEM modeling and experimental determination of the two tests of the composite material characteristics used for the impeller of aerodynamic compressors.

Rapid heat cycle molding (RHCM) is a special molding process capable of producing molded plastic parts with high surface quality and improved weldline strength and appearance. This study investigated the influence of the weldline on the tensile strength of RHCM and conventional injection molded (CIM) components. The test specimens with and without a weldline were cut from RHCM and CIM parts for scanning electron microscopy (SEM) imaging to characterize the structure and dimensions of the weldline and tensile testing. The tensile testing results showed that the weldline reduced the tensile strength, but RHCM decreased the tensile strength reduction effect of the weldline. There was no distinguishable difference between the two molding processes for the tensile strength of specimens without a weldline. In addition, a thin surface layer of material containing the V-notch at the weldline was removed from the RHCM and CIM parts to examine its effect on the tensile properties. The thinned-out specimens with a weldline showed improved tensile strength, and specimens without a weldline showed decreased tensile strength, compared to specimens with the original full thickness.

Closed cell polyurethane foams with densities of 100, 140 and 325 kg/m3 were tested in compression at speeds from 0.6 to 500 mm/min. Digital image correlation (DIC) is used to determine the engineering characteristic curve, modulus of elasticity, maximum stress, and the deformation bands that appear during deformation and prior to the final failure of the specimens. By using this procedure both global and local phenomena are observed and analyzed. While each specimen is compressed, the damage behaviour of the foams is directly observed in different stages.

In the first part of the paper we touch on the influence of the processing temperature by injection of HDPE, of PMMA, and of PC+ABS blend on some mechanical flexural properties, while the other factors which could influence the injection remain unchanged. In the second part of the paper, we present the influence of the subsequent pressure in the injection of HDPE, PMMA, and PC+ABS blend on mechanical bending properties, while the other factors which could influence the injection remain unchanged. The HDPE samples were obtained at the following injection temperatures – 180, 190, 200, 210 and 220°C – and at the following subsequent pressures – 800, 900, 1000, 1100 and 1200 bar. The PMMA samples were obtained at the following injection temperatures – 220, 230, 240, 250 and 260°C – and at the following subsequent pressures – 450, 550, 650, 750 and 850 bar. The PC+ABS samples were obtained at the following injection temperatures – 230, 240, 250, 260 and 270°C – and at the following subsequent pressures – 500 bar, 600 bar, 700 bar, 800 bar, and 900 bar. We have used the method of determining flexural properties, such as the flexural stress, flexural deformation, and flexural modulus. It was observed that in the case of HDPE, the highest values of flexural stress were registered at its lowest temperature (180°C) – the flexural stress recorded 28,3038 MPa – and at the highest value of subsequent pressure (1200 bar) – the flexural stress recorded 29.3380 MPa. PC+ABS acts in a similar manner to HDPE. In the case of PC+ABS, 240°C recorded the highest value for the flexural stress of 89.2246 MPa, while the highest subsequent pressure of 900 bar recorded the highest value of flexural stress of 88.5375 MPa. In the case of PMMA, the highest value for flexural stress (124.2563 MPa) was recorded at the lowest processing temperature (220°C) and at the subsequent pressure of 550 bar, where the value of the flexural stress was of 110.5376 MPa. In the case of HDPE and PC+ABS, the flexural deformation is barely influenced by the processing temperature and the subsequent pressure, whereas in the case of the PMMA, the processing temperature and the subsequent pressure influence the flexural deformation. The increase in the subsequent pressure leads to a slight increase of the flexural modulus in the case of the three studied polymers. The increase in the processing temperatures of HDPE and PC+ABS leads to a slight decrease of the flexural modulus, whereas in the case of the PMMA, the increase in the processing temperatures barely influences the flexural stress.