Volume 45, Issue 2

Abstract: This paper presents a procedure for the calculus and dimensional optimization using finite elements analysis of a polymeric retractable rod which replaces a metallic one. This rod is an element of the front auger embedded in a technological equipment. The mechanism is 3D modeled in SolidWorks. CosmosMotion is then used to simulate and analyze the motion of the mechanism and to calculate the loads acting on the rod during its movement. These loads are then exported in CosmosWorks – a finite elements analysis software – which is used here to perform stress analysis and to optimize the retractable rod’s dimensions. Keywords: polymers, optimization, finite elements analysis

Abstract: Polyphenols have antioxidant character due the presence of several phenol functional groups. In human health, they are thought to be useful in combating oxidative stress, a syndrome causative of neurodegenerative and cardiovascular diseases. The main source of polyphenol antioxidants is nutritional, since they are found in most vegetables and fruits. We used tannic acid as polyphenol model. The polyphenols are encapsulated in chitosan matrices because chitosan is a natural bioactive material and it is pursued to release the polyphenols only in a certain medium. In this paper, the obtaining strategy of chitosan nanostructurate membranes with tannic acid, as Controlled Delivery System, is presented. Keywords: chitosan, cationic surfactant, tannic acid, morphological analysis

Abstract: Implementation of composite materials, especially of glass fibers reinforced ones, lead to replacement of classic materials, whose supplies are more and more limited. The machinability, as well as the machining procedures, of polymeric composites depend on various factors, such as matrix and reinforcing element types; the orientation of reinforcing elements, manufacturing method, etc. Thermal phenomena, occurring while machining, are very important, because the temperature into the cutting zone must not exceed certain value corresponding to vitrifying temperature. So, this paper presents the most important aspects required in order to obtain a mathematical model of temperature, as function of machining parameters, in cylindrical – face milling of glass fibers reinforced polymeric composites. Keywords: polymeric composite, glass fibres, milling, regression function

Abstract: Both the theoretic elements of an interferometric method for the refractive index determination based on a Fabry-Perot etalon and the procedure of the Fabry-Perot cell obtaining are described in this paper. The results obtained by this method for PVA isotropic foils and for PVA foils including small amounts of potassium iodide are given here. Keywords: PVA, FPE, refractive index, isotropic materials

Abstract: Full denture casting currently represents a technological alternative. The casting system we tested usually uses reversible hydrocolloids for investing wax patterns. Besides the system’s own advantages, the authors also noticed certain errors consecutive to casting, materialized in lack of substance and the development of porosities on the mucosal facets of the complete denture bases. Keywords: casting, full dentures, errors

Abstract: The aim of the experimental study described in this paper was Lamb wave method evaluation for damage/defects detection of epoxi/glass composites. Can be used piezoelectric transducers - actuator/sensor - glued on the surface of investigated composite, using transmission mode. The chosen control parameter was the sensor signal attenuation because of defects that exists in examinated samples. The proposed monitoring system was efficiently in the detection of damage/defects such as holes, allowing for damage/defect size estimation. Keywords: composites damages detection, Lamb wave

Abstract: The epoxy resin EPO 99B, known under the name REZOLIN, is one of the main materials used in manufacturing/modeling the axial runner of hydraulic machines. The simplest device of this kind is the inducer employed to reduce the cavitation intensity of the main pump impeller. The geometry is determined from hydrodynamic conditions, is a very complex one and is subjected to dynamic mechanical stress (vibrations). As a result of those conditions the resin must have good mechanical and technological qualities. It was realized at SC Elba SA Timisoara, and is made from a mixture between the resin H9951 and a fortifier. The obtained inducer runners have been tested in air at the Hydraulic Machinery Laboratory of Timisoara Polytechnic University, and supplementary the basic material was tasted to cavitation erosion resistance. As a result, our work takes into considerations both the impeller hydrodynamic performances and the behaviour of the manufacturing material (resin EPO 99 B) to cavitation erosion. Key words: epoxy resin, cavitation erosion of plastic material, inducer runner performances

Abstract: Poly(betaine)s based on poly(N-vinylimidazole) (PNVI) and poly(4-vinylpyridine) (P4VP), namely poly(carboxybetaine)s with one (PNVIB-1 and P4VPB-1) and two (PNVIB-2 and P4VPB-2) methylene groups between the opposite charges were prepared. Poly(betaine)s represent high dipolar materials with wide spectrum of unique and specific properties. Some of such properties are shown in this paper. Thus, the PNVIB-1 and P4VPB-1 are insoluble in water but the addition of salts promotes their solubility, whereas PNVIB-2 and P4VPB-2 are soluble both water and aqueous solution of salts as well as in methanol. Also, for all the polybetaines one of the most interesting properties in solid state is the formation of homogeneous blends with some inorganic salts in equimolecular amounts, they being a new type of organic-inorganic hybrid materials. Keywords: poly(carboxybetaine)s, anti-polyelectrolyte behaviour, poly(zwitterions), organic-inorganic hybrids

Abstract: A new type of polyurethane metal-complex was prepared by incorporating the transition metal ions such as copper (II), cobalt (II) and nickel (II), into polyazomethine-urethane-urea, containing functional groups. Polyazomethine-urethane-urea (PAMU) was synthesized from 5,5’-methylene-bissalicylaldehyde (MBS) by reaction with an urethane prepolymer based on polyethylene adipate diol (PEA), hexamethylene diisocyanate (HDI) and ethylene diamine (EDA), in DMF as solvent, using 0.5 wt % dibutyltindilaurate (DBDTL) as catalyst. The polymeric Schiff base was converted to the chelates of the metal salts. This complex was performed by mixing of the polyazomethine-urethane-urea, containing functional groups, with the metal salts in DMF as solvent. The polyurethane metal-complexes were characterized by FT-IR spectroscopy and elemental analysis. The polymer property investigated was their thermal stability which was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The aim of this work is to present a general idea of the various methods of preparation, properties, and applications of metal-containing polyurethanes. Keywords: polyazomethine-urethane-urea, chelate polymers, metal-polymer complex

Abstract: The applications of membranes and membrane processes in advanced separations from biotechnology have gained lately a great importance determining their inclusion among the top technologies. This paper presents an original variant for preparation of some affinity membranes from acylated polysulphone and brominated polyphenileneoxide, with immobilized starch as affinity ligand for biospecific separations. Keywords: membranes, phase inversion, affinity ultrafiltration , ligand

Abstract: The aim of this paper is to present a proper methodology for obtaining active mould parts. The originality of the paper consists in the fact that building these active objects starts from some distinctive marks (machine parts) for which there’s no technical documentation. Using reverse engineering procedures (scanning and reconstruction) for polymeric material machine parts and rapid prototyping procedures by material sampling, we will finally obtain both the wanted distinctive mark and its active elements. Keywords: reverse engineering, rapid prototyping, polymeric material, mould

Abstract: Two new polymeric materials were prepared by coating of polyurethane (PU) with a collagen (COL) gel and a mixture of collagen-elastin (COL/EL). The bioactivated polymeric materials were examined by scanning electron microscopy (SEM) for pore morphology. They were also comparatively assayed for porosity, mechanical properties and biodegradability in the presence of bacterial collagenase. In vitro biocompatibility studies were performed in a primary culture of human dermal fibroblasts using spectrophotometric and light microscopy methods. These new polymeric materials showed good tensile strength, biodegradability and a high in vitro biocompatibility. They can be used in the field of medical devices where such physical and biological features are necessary. Key words: polyurethane, natural polymers, collagen, elastin, biocompatibility, biodegradability

Abstract: The paper presents two methods for similarity measurement of plastic textured images, and also for identification and localization of defective region in textured images. In order to have less sensitive statistic features regarding to rotated image, we introduce the notion of average co-occurrence matrix. With the purpose of algorithm validation, the images are divided into four equivalent regions. For the proper region similarity measurement, a decision theoretic method is used. In the fractal approach, we consider a new fractal dimension derived from box-counting algorithm, named effective fractal dimension, with an increasing efficiency for texture classification. Two experimental studies, one for statistical features and one for fractal type features, in a plastic simulated wood case, validate the algorithms. The algorithms are implemented in Visual C++ and Matlab. They allow the simultaneously display of both the investigated region, and the Euclidian distance between this and a reference image. The results confirm the fact that the distances between the regions without defect are relatively small, and the distance between a region with defect and a region without defect is relatively large. Also, the results show that features extracted from average co-occurrence matrix and the effective fractal dimension have a good discriminating power. Keywords: texture similarity, statistic features, fractal dimension, plastic simulated wood, defect detection

Abstract: This paper presents the effects of high energy irradiation on polyvinylchloride samples, some of them containing filler (1 and 5 % mica). The generation of dipoles as oxygenated radiolysis products modifies electrical behavior of polymer matrix. The presence of mica influences the rate of oxidation by decreasing the progress in the accumulation of oxygenated products. The values of volume resistivity, dielectric constant and loss factors are consequently changed as the mica content differs due to the adsorbent action of filler. Keywords: PVC, mica, irradiation, volume resitivity, dielectric constant, loss factors

Abstract: The three new polyanionic polymer conjugates were synthesized by the chemical bonding of some N-mustard derivatives of di-(b-chloroethyl)-amine and tri-(b-chloroethyl)-amine with poly(maleic anhydride-alt-vinyl acetate). The chemical structure of the compounds obtained was verified by FTIR, H1-NMR and elemental analysis. Keywords: poly(maleic anhydride-alt-vinyl acetate) conjugates, alkylating agents

Abstract: The paper investigates the influence of rubber elastic properties on modal behaviour of truck tyres. Hyperelastic models and numerical values of coefficients in these models used for defining rubber hyperelastic behaviour are presented. The choice of the appropriate hyperelastic model to be introduced in the tyre finite element model is motivated. The main characteristics of the finite element model of a radial truck tyre are presented. A series of modal analyses is performed, in which elastic properties of tread rubber are modified in a wide range. Finally, the influence of tread rubber elasticity characteristic values on natural frequencies and mode shapes of truck tyres is analysed. Keywords: tyre, hyperelasticity, modal behaviour, finite element model

Abstract: In this paper is presented an analytical model, which makes the similitude between the DTMM theory of composite multilayer bars and the FSDT theory used in the study of composite bars and plates in a dynamic regime. The authors proposed a numerical application of the model, for two different bars made from glass-epoxy reinforced composite. The experimental validation of theoretical results was made on a composite bar as a component of a quadrilateral mechanism, whereon the leading element describes a rotation motion with the constant angular speed. Keywords: composite materials, vibrations, movement in a plane

Abstract: The frictional factor of new hip endoprosthesis was measured using one hip testing device designed in Biomechanics Laboratory of Medical Bioengineering Faculty. Hip simulator respect physiological condition (variable load, variable motion). The friction factor value for fluid film regime through the gait cycle was founded variable like a consequence of UHMWPE visco-elasto-plastic behaviour. Keywords: friction factor, gait cycle, visco-elasto-plastic behaviour