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This research aims to establish the behaviour of geomembranes used for base sealing and for covering municipal waste facilities. The geomembranes used for base sealing are subjected to leachate pressure and to the action of chemical and microbiological pollutants. Geomembranes used for covering waste facilities are subjected to the action of precipitation water and released gases. This paper analyzes the following: the permeability mechanism of geomembranes made of polymers, the process of water vapours diffusion through polymers, diffusion flow, characteristic of permeability and influencing factors. The study also presents data on the permeability of some polymers - the most commonly used in the structure of geomembranes used in household waste facilities - as well as some of the results of ongoing research on the behaviour of high density polyethylene geomembranes in contact with the waste facilities’ leachate. Diffusion was determined by measuring the weight of the vessel (water loss) daily for 30 days. The polymer influences the permeability and diffusion through the molecular and intermolecular chemical structure, the packing density, the degree of crystallinity, the crosslinking density and through the flexibility of the macromolecular chains. The results show that the permeability of polymeric geomembranes is comparable to that of a microporous material (cement stone, bentonite).

This paper describes the preparation of three- component hybrid copolymer beads, with water purification features. These newly developed hybrid beads were prepared starting from a mixture of poly(acrylonitrile- co- methacrylic acid) (PAN-co-PMAA), polyvinyl alcohol (PVA) and magnetite (Fe3O4), respectively. The preparation itself involved a Wet Phase Inversion (WPI) process. A Pseudomonas sp. strain was immobilized onto previously mentioned beads, before and after activation of the beads surface with glutardialdehyde, and afterwards used for the amendment of simulated water bearing an azo- blue dye, i.e. Acid Blue 93. In order to highlight the immobilization of Pseudomonas sp. strain, FTIR spectra and TGA results were recorded. CFU measurements as well as SEM images further provided evidence towards the occurrence of immobilization. The biodegradation studies of Acid Blue 93were carried out by means of UV spectroscopy at various contact times (24; 72 and 144 h) of the hybrid beads with the targeted dye.

How the particle size and volumetric ratio of silicon carbide (SiC) powder additions will strengthen polymethyl methacrylate (PMMA) is unclear. The purpose of this in vitro study was to optimize the reinforcement parameters of PMMA with SiC powder by using the Taguchi experimental design method. Particle size, volumetric rate, silane coupling rate, and mixing type were determined as parameters that would affect the reinforcement of PMMA with SiC powder. Using the Taguchi L9 orthogonal array, test specimens with different parameter combinations were fabricated and tested. The fracture load (in newtons) of each specimen group was recorded with the 3-point bend test. The thermal conductivity values of 60x50-mm and 3-mm-thick rectangular specimens were measured by using the Linseis THB100 thermal conductivity unit. The thermal diffusivity values were then calculated. Thermal analysis indicated improvement in the thermal conductivity of PMMA after reinforcement with SiC. The maximum thermal diffusivity was obtained with 15% SiC powder by volume. Thermal conductivity and flexural strength increased with an increase in particle size. The maximum flexural strength value was obtained with 5% SiC powder by volume. Increasing the particle size of the filler SiC powder resulted in increased thermal conductivity and flexural strength. Increasing the SiC filler powder by volume increased the thermal conductivity of PMMA but reduced its flexural strength. This study helped determine the optimum conditions for the use of SiC powder. Knowledge of the importance of these variables will help in more effective modification of denture base resin with SiC powder to improve heat transfer without adversely affecting strength.

Rapid innovations in 3D printing technology have allowed highly complex parts to be manufactured quickly and easily, particularly for prototyping purposes. Fused Deposition Modeling of thermoplastic materials is one of the most commonly used techniques in three-dimensional (3D) printing. The major aim of Fused Deposition Modeling (FDM) is to design and manufacture usable parts for fields such as engineering and medicine. Therefore, it is essential to investigate the mechanical properties of such FDM processed structures. One of the most commonly used materials currently on the market is Polylactic Acid (PLA). The main purpose of this paper is to investigate the effects of aging and heat treatment on the tensile properties of PLA printed test specimens. The tensile properties of parts manufactured by the 3D printer are influenced by various parameters such as extrusion temperature, infill density, building direction, layer height, etc. A total of 96 specimens were built by altering building orientation and layer height to estimate and compare the tensile properties of the printed parts. To investigate the aging effect, 30 of 96 specimens were printed 6 months before the tensile experiment. Half of both aged and new specimens were cured in an oven at 57.5 [¢ªC] for 3 hours while the other half endured no heat treatment. After the performed measurement, it can be concluded that heat treatment generally improves structural strength of the printed parts, while aging decreases it. However, these effects are highly dependent on the layer thickness and printing quality. The tensile test is conducted according to the ASTM D638 standard. The fractured samples were further characterized using an electron microscope.

Polymeric materials are synthetic macromolecular products, of which, by mechanical or thermal processing, objects of various shapes can be obtained, with wide uses in industry and commerce. This paper deals with the roughness of surfaces obtained during drilling of three polymeric materials: polyamide - PA6, polyacetal - POM-C and high density polyamide - HDPE 1000. In the experimental research was used a EMCO MILL 55 milling machine numerical controlled and HS steel helical drills with two straight cutting edges with the diameter of Ø8 mm and Ø10 mm, respectively. Experimental determinations consisted in drilling of the polymeric materials by modifying some parameters of the cutting regime, and determining the roughness of the surface of the holes machined, using the Mitutoyo Surftest SJ-210 rough meter. The purpose of the paper is to predict the roughness of the machined surfaces as one of the important surface quality indicators by using a geometrical model and an artificial neural network (ANN) methodology.

In the context of an extremely diverse offer of composite materials, the clinical reality permanently offers data about the way in which the individual feeding behavior, correlated with the salivary structure definitely have an impact on the structure, namely the quality of fillings made of various composite materials.The purpose of this study is represented by the analysis of the behavior of 6 types of composite materials that are frequently used in the dental medical practice in the presence of an acidic pH. The composite materials analyzed were Premise (Kerr) - P1, Polofil Supra (Voco) - P2, Nexcomp (Meta Biomed) - P3, Point 4 (Kerr) - P4, Pekalite (Heraeus Kulzer) - P5, and Progress (K.B. Mutsumi) - P6. The images of scanning electron microscopy clearly indicate that all samples are affected by acidic conditions (pH 4) after a moderately, but continuous exposure of 3 months. Signs of abrasions structural deterioration and leaks are obvious after pH 4 saliva treatments within all samples and magnifications, being marked by texture decay, rust-like presentation, and shallows, holes and cracks rise and enlargement. The intensity of deterioration processes varies between the studied commercial samples, with Pekalite (Heraeus Kulzer) followed by Point 4 (Kerr) being the most resistant to degradation in the current experimental conditions.

A series of four drug release formulations based on 5-fluorouracil encapsulated into a chitosan-based matrix were prepared by in situ hydrogelation with 3,7-dimethyl-2,6-octadienal. The formulations were investigated from structural and morphological aspects by FTIR spectroscopy, polarized light microscopy and scanning electron microscopy. It was established that 5-fluorouracil was anchored into the matrix as crystals, whose dimension varied as a function of the crosslinking density. The in vitro drug release simulated into a media mimicking the physiological environment revealed a progressive release of the 5-fluorouracil, in close interdependence with the crosslinking density. In the context of Pharmacokinetics behavioral analysis, a new mathematical procedure for describing drug release dynamics in polymer-drug complex system is proposed. Assuming that the dynamics of polymer-drug system’s structural units take place on continuous and nondifferentiable curves (multifractal curves), we show that in a one-dimensional hydrodynamic formalism of multifractal variables the drug release mechanism (Fickian diffusion, non-Fickian diffusion, etc) are given through synchronous dynamics at a differentiable and non-differentiable scale resolutions. Finally, the model is confirmed by the empirical data.

The development of 3D printing technologies has gained considerable momentum. Almost every technical-scientific field uses this technology. The technology of 3D printing thermoplastic materials (or fusible filaments - FFF), is based on the realization of the parts by depositing successive layers of extruded filament at temperatures corresponding to the viscous aggregation state. One of the research activities of the CERAS research center is the realization of collaborative drone systems, drones capable of moving in each of the three unstructured environments: aerial, terrestrial aquatic / underwater. This paper presents a study on the choice of the type of thermoplastic material, for making the structural elements (chassis) of an underwater Rover. The need for this study arose from the fact that the design and construction of underwater vehicles is generally demanding. The materials must be characterized by resistance to compression / stretching / shearing, as in underwater environments the existence of currents, pressures (with increasing depth of immersion). Also, the materials must be chemically neutral, because in aquatic environments we can find various chemicals spilled in water (intentional or not) and finally salinity.

In this study, computer-aided engineering (CAE) simulation software and the design of experiments (DOE) method were used to simulate the injection molding process in terms of the melt flow length, using a spiral part. Process parameters such as melt temperature, mold temperature, injection pressure and mold cavity thickness were considered as injection molding variables. A predictive model for the flow length was created using a three-layer artificial neural network (ANN). The ANN model was trained with both simulation and experimental data, and the predictive performances were compared in terms of correlation coefficient, root mean square error and mean relative error. The cavity thickness and melt temperature were found to be the most significant factors for both the simulation and the experiment, while the injection pressure and the mold temperature had little effect on the flow length. The ANN model trained with Moldex3D data shows a significantly higher prediction capacity than the ANN model trained with experimental data. However, the melt flow lengths predicted by the ANN model for both Moldex3D and Moldflow simulation data are statistically significant, indicating that the proposed prediction methodology, which combines the ANN model, DOE method and the CAE simulation technology, can effectively predict the flow length of injection molded parts, with a small number of data.

In this study, five ultrafiltration membranes (polysulfone, cellulose acetate and polyethe-rsulfone) were tested in the treatment of aqueous protein solutions similar to wastewater from fermentation industries. The experiments were made in tangential flow filtration. The permeate flux for the five membranes tested at the optimum pressure of 3 bar decreased due to the effect of clogging the pores by the macromolecular protein solutions. Cellulose acetate membranes showed the lowest permeate flux (Ac-Cel1=152.4 L/m2.h and Ac-Cel2=40.3 L/m2.h) which doesn’t recommend them for the ultrafiltration process of bovine serum albumin. When a polysulfone membrane was used in several cycles of protein-containing wastewater ultrafiltration, the permeate flow decreased progressively from one cycle to another due to the internal clogging of the membrane (501.6 L/m2.h up to 444.0 L/m2.h). Regarding the ultrafiltration of protein solutions with a suspended yeast content, the clogging was predominant on the membrane’s surface, which results in a decrease of the permeate flux by over 50%.