Volume 44, Issue 4

Abstract: Among the composition and morphological structure field of biomaterials, the biodegradable biocomposites based on, synthetic and natural polymers as biocompatible spongious matrices has been studied. The biodegradable synthetic polymers have good mechanical properties, low toxicity and a controlled degradation kinetic. However, these polymers are hydrophobic and do not exhibit adequate surface for cells attachment and proliferation because of receptors absence for cells recognition. The natural polymers show good cellular interaction and high hydrophilicity. The advantages of biocomposites made of both synthetic and natural polymers are holding both physico-chemical properties of synthetic polymers and biocompatibility, cellular adhesion properties and variety of biological interactions induced by the contact between cells and natural polymeric support. The aim of this study was the synthesis of biocompatible porous structures by compounding synthetic polymers - (poly(L-lactic acid) (PLLA), poly(D,L-lactic-co-glycolic acid) (PLGA) which are biocompatible, biodegradable but hydrophobic, with natural polymer – collagen, the main protein of extracelullar matrix. The biocomposites were prepared in a polymer: collagen ratio of 2:1 by adding synthetic polymer solution, solved in chloroform, to aqueous collagen gel. The synthesis of biocomposite matrices was achieved by lyophilizing of synthetic polymer/collagen blends after dialyse against 1M KCl. Both uncrosslinked and crosslinked samples were prepared. As standard sample the uncrosslinked and crosslinked collagen matrices were chosen. The morphology of biocomposite matrices PLLA/collagen, PLGA/collagen was characterized by SEM in order to investigate the macro-, micro and nanoporosity. Physico-chemical characterization was focused on thermal stability (DSC and TGA) and surface hydrophilic character by water vapours absorption, water vapours permeability and water absorption. Keywords: biocomposites, collagen, biodegradable synthetic polymers

Abstract: This paper presents the results of the experimental researches made on an extruder for pasta, in which the extrusion die has the active extrusion surfaces from two different materials: plastic and metallic. The subject is focused on polytetrafluoroethylene, to indicate the advantages of this material comparative with bronze. The experimental part consists of diameter measurements of the intern extrusion holes with the optic microscope. Keywords: polytetrafluorethylene, bronze, extrusion, die

Abstract: The paper presents experimental data regarding a number of five new polymeric termo-resistant pigments synthesized by condensation of Perylene 3, 4, 9, 10-tetracarboxylic dianhydride with 2-Cl-p-phenilendiamine in various molar ratio. Reaction products were purified and characterized by elemental analysis, UV-VIS, IR and thermal analysis. Keywords: perylene 3, 4, 9, 10-tetracarboxylic dianhydride, 2-Cl-p-phenilendiamine, polymeric thermoresistant pigments

Abstract: The concept of thermal homogeneisation efficiency, hht was defined, giving an indication on the thermal homogeneity realised by a certain zone through the heat generated by internal friction. Its optimal value corresponds hht = 1. This concept was then applied to the calculus of thermal homogeneity at the flow of a power-law non-Newtonian polymer melt, through a rectangular slit, similar to the flow over the barrier flight f. The relationships obtained for temperature rise due to heat generated through internal friction allowed the calculus of hht in a given case. Kewords: thermal homogeneity, internal friction, polymer melt

Abstract: This work presents the results obtained from experiments of rigid PVC stabilization both lead stabilizer and earth alkaline carbonates as co stabilizer. Efficiency of stabilizers was tested by dynamic tests (roll mill processing or Brabender plastograph) and static test (thermogravimetric analysis). Both types of test were in concordance from point of view of stabilization efficiency and from thermal analysis can be predicted the thermal lifetime of PVC products. This is an important fact for durable usage or for recycling products made from PVC. Keywords: PVC stabilizers, roll mill, Brabender plastograph, thermal analysis, lifetime prediction, isoconversional method

Abstract: In this paper it was established the influence of the processing temperature of the injection moulding on the in-mould pressures and on the characteristics of the obtained items used for high performance sport products. The processed polymers were: polypropylene (PP), polyamide 6,6(PA66), polycarbonate (PC), polyurethane (PU), polyoxymethylene (POM, polyacetal). The injection machine employed was ENGEL G/11/10/116/3 produced in 2002. For the correct temperature measurement in the injection cylinder nozzle a DYNISCO Ti422J thermocouple was used and for the determination of the cavity temperature, a thermocouple 2024T model, produced by Digitron Instrumentation Ltd. was used. The mould cavity pressure was measured with a transducer model IDA, produced by Dynisco Europe GmbH. Keywords: injection moulding, pressure, temperature

Abstract: The paper argues the necessity of 3-dimensional inspection of injected plastic parts, presenting the special demands and particular condition related to the specificity of part material nature. A measuring strategy on the coordinate measuring machine is presented for verifying the position, dimensional accuracy and shape of the circular holes, slots and the line form for plastic parts used in the automotive industry due to the dimensional changes caused by shrinkage and warpage. The reverse-engineering technique applied in the try-out phase to the production launch is also presented. Keywords: injection, shrinkage, warpage,3-D measurement, reverse engineering

Abstract: Highly active, new bis(2,6-di- tert-butyl-4-methyl-phenoxy)aluminum methylphosphonate sterically hindered aluminum catalyst was developed for both, homo- and copolymerization of propylene oxide with carbon dioxide. The behaviour of this catalyst compared with that of bis(2,6-di-tert-butyl-4-methylphenoxy)aluminum alcoxide-based catalyst was investigated. The former shows much higher catalytic activity in chemical fixation of carbon dioxide than the latter. According to the experimental data, the unavoidable propylene carbonate resulting in an appreciable proportion in propylene oxide - carbon dioxide copolymerization reaction initiated by sterically hindered aluminum catalysts, seems to appear not at the back-biting reaction of the growing chain. Apparently the reaction temperature or the reaction components molar ratio did not influence the propylene carbonate proportion. Keywords: propylene oxide, carbon dioxide, aluminium catalysts

Abstract: The paper presents the results of experiments in obtaining some plastic mixtures with high quality characteristics, which should lead to products of complex geometry and improved chemico-structural features, meant to be used in the processing industry-helical milling machining by applying the formation technology in a plastic state. The paper presents the physico-chemical, mechanical and structural features of the mixtures of hard K20 alloys, the compositional networks of the powder making system and of the multi-component organic binder, all these being accomplished according to ICEM’s technical view. To improve the toughness, the tenacity and the wear resistance of the parts devoted to metal working industry, the helical mills were coated with some extra-hard layers by TiC, TiN/Ti2N deposits on hard alloy support by a new PVD technique which supposes a combined magnetron sputtering and ion implantation (CMSII). Keywords: plastic mixtures; helical mills; extra hard layers; magnetron sputtering; ion implantation

Abstract: In this paper the mechanical models for nanocomposites are discussed focussing on the main restrictions of the first order models. It is proposed, according to some results for the second order models, to include in the mechanical approach some geometrical parameters to handle the transition from to scale to scale, but also to refer the modelling to an expedient class of functions which naturally describe the scale transition. Keywords: nanocomposites, first order models, second order models, wave propagation, wavelets

Abstract: Ultra-high molecular weight polyethylene generally cannot be processed by injection moulding because of its high viscosity. In this paper, the formability of GUR-UHMW-polyethylene is numerically investigated during the injection moulding in an acetabulat cup. A number of numerical simulation tests have been performed on different acetabular cups to select the most appropriate process parameters and to optimize the injection moulding process. The numerical analysis demonstrates that the GUR-UHMW- polyethylene can be processed by injection moulding. Keywords: injection moulding, finite element analysis, UHMW-PE

Abstract: The thermal decomposition behaviour of some phosphorus-containing polyesters and a polyesterimide was studied using thermogravimetric analysis in air at several heating rates between 5°C/min and 20°C/min. The results of this study, realized for polyesters with phosphorus linkage as pendant group, were compared with the behavior of some polyesters having the same backbone structure, with phosphorous in the main chain, respectively without phosphorous. A kinetic model of the reaction order was also proposed for thermal degradation of studied polymers by using Vyazovkin method. Keywords: phosphorus-containing polymers, thermal degradation, flame retardant properties

Abstract: Aromatic hydrocarbons especially 1,2 benzanthracene and perylene were effective in suppression of carbonyl and hydroperoxide formation upon irradiation, while carbon structures (carbon black and graphite) seems to produce increased radiation degradability, as it was shown by IR data. Pyrene and perylene induced increased stability to thermal oxidation subsequent to irradiation. The radiation induced formation of some hydroxyl groups grafted on degraded polynuclear structure has been supposed to explain the observed increased stability. Several changes in IR absorption bands observed with these irradiated hydrocarbons support this hypothesis. Keywords: chemiluminescence, aromatic compounds, degradation, polyethylene

Abstract: In the generation of new materials replaceing the metals, taking into account their characteristics and future perspectives, one should pay a special attention to the composite materials, which were named consolidated plastic materials, just a short time ago. This paper emphasizes that the quality of the drilling tools and the geometry of their active part, the dimensional precision and of geometric form and also the quality of the surfaces processed by drilling, depend especially on the nature of the composite material and of the reinforcing fibers. Keywords: composite material, drilling, machining, wear

Abstract: In this study the polymer transport dynamics in a 2D lattice model is investigated. The dependence of the polymer escape time through a nanometer pore on the stiffness and the monomers number of the polymer is demonstrated. We have also proved the major effect of superimposed electric field on the polymer translocation. Keywords: 2D lattice model, Langevin equation, nanopore, transport phenomena, translocation time

Abstract: The paper deals with the synthesis and characterization as polymer processing aids, i.e. as plasticizers and/or lubricants, of some mixed (unsymmetrical) diesters of adipic acid by using aliphatic alcohols of variable length, such as C4, C6, C2-6, izo C10 and izo C13, along with complex aliphatic-aromatic alcohols, like 2-phenoxyethanol, 2-[(o-sec-butyl)phenoxy]ethanol and 2-[(p-nonyl)phenoxy]ethanol, respectively. The diesters derivatives obtained this way showed plasticizing and/or lubricating properties. The variation of such properties was studied by varying the polar / unpolar ratio within each structure of the considered product. Interesting correlations were recorded and the theoretical premises were fully proved. Keywords: unsymmetrical adipic diesters, plasticizers, lubricants, phenoxy-ethanols

Abstract: Lubrication aspects, in extreme operating conditions, highlights important problems concerning bearings design or greases behaviour management for given operating conditions. The researches that were done in the last period were focused on greases service life and behaviour versus rolling bearings operating conditions but, it must be emphasized, that some particular aspects such as the presence of the electrical fields were less studied. Some results in this specific area were previously forwarded by Prashad who highlighted issues such as greases resistivity modifications with time, particular bearings and lubricating greases damaging mechanisms. Aspects concerning temperature influence on grease resistivity, correlations between greases structural, physical and chemical deterioration and bearings specific failures, in the presence of the electrical field, are questions that must be answered. These problems are very important because electrical rotating machines support bearings reliability is strongly dependant on greases service life and performances. The paper presents some correlations between the electrical field characteristics and electrical motors rotors support rolling bearings greases deterioration based on lubricant’s SEM and raceways microscopical analyses. Starting from these results it can be concluded that rolling bearings deterioration under the influence of the electrical field is a complex phenomenon with effects, both, on lubricating greases and bearings rolling contact surfaces. From this point, a greases deterioration model, in the presence of the electrical field, will be proposed. Keywords: lubricating greases, electrical field, deterioration

Abstract: This paper presents studies regarding the behaviour at heat treating of an AlCu4Mg1 aluminum alloy. The experiments were made on laboratory conditions and can be applied in industry. The proposed methodology can be resumed in: adopting the heat treating technology for the proposed alloy; choosing the necessary working installations in order to realize the heat treating for the specified alloy; choosing the tools and the machines used for studying the chemical and mechanical characteristics; programming the experiment and analytical interpretation of the results. For experiments, was used a study charge (9 treated parts) and a test part (a non treated part). Every part from the study charge had a particularly final heat treating technology. Test part is not treated and the mechanical characteristics are determined in this situation. As a conclusion, the paper presents the algorithm for applying the optimum heat treating in order to obtain the necessary properties for the working parts. Keywords: aluminum, plasticity behaviour, heat treating, chemical composition, elasticity

Abstract: Due to their important and special characteristics composites have known a continuous development lately. Consequently there has been given great attention to improve, both, their manufacturing and machining technologies. In machining, milling represents an important procedure and, as there are not many data concerning process parameters dependence, some statistic models were considered worth to be determined. So, there has been studied Romanian glass fiber reinforced polymeric composites and have been obtained two mathematical relations of surface roughness dependence - Ra parameter- on some milling process variables. Keywords: composites, glass fibers, milling, surface roughness

Abstract: The paper deals with the synthesis of aminophosphonate polymer-silice hibrid. In the first step chloromethylated polysulphone was chemically functionalized with aldehyde groups by direct oxidation with DMSO, followed by “one-pot” reaction of polysulphone aldehyde with diphosphite and (3-aminopropyl) trimethoxysilane. Keywords: aminophosphonate groups, polysulphone, “one/pot” reaction

Abstract: Failure mechanisms for composite materials and especially for laminated composites are different and more complex than for homogeneous and isotropic materials. That is why modeling and analysis of such structures are done having as main goal determination of the local stress states in the zones where high stress gradients occur: supports, points where load are applied, geometric discontinuities, junctions etc. In this paper the authors propose a methodology for the geometric and constructive optimization of the junctions in structures made from laminated composite materials. On the other hand due to the fact that the apparition of discotinuities in structures could lead to macro failures of the continuum, the modelling and analysis of discontinuities can be made using techniques adequate for local problems, such as sub structuring and sub modeling and the use of finite element method. Consequently, the purpose of this paper is to underline the importance of the study of discontinuities in mechanical structures and to present a methodology of approach (one of the many that can be used). Keywords: laminated composites, local stress states, macro failures, finite element method

Abstract: Thermoplastic materials are used more and more in the technology of complete or removable partial dentures due to their superior qualities. We have tested an acetal resin, two polyamide resins and polyamide prefabricated clasps. By injection, we have manufactured several removable partial dentures without metallic structure. Thermoplastic resins are suitable for manufacturing a wide range of removable partial dentures without metallic structure, in optimal conditions of biocompatibility. Key words: removable partial dentures, thermoplastic materials, molding-injection devices

Abstract: In this paper, aspects related to the energy absorption optimization of SafetyPlastic are presented. SafetyPlasticÒ is a patented impact energy absorbing technology currently used in the automotive industry as a countermeasure for occupant protection on head and side impact events. The optimization process is focused on properly changing the energy absorber wall thickness and shape, in order to promote an efficient buckling mode on the side walls. By using optimal thickness values along the height for different layers in which the particular absorber was divided, an outstanding improvement in Head Injury Criterion has been recorded. The results and the optimization procedure can be extended to various recesses shapes pertaining to the energy absorber. Keywords: optimization, polymeric energy absorber, buckling, finite element analysis

Abstract: This paper presents a preliminary research activity to approach a new industrial technology to incinerate humid solid waste coming from a standard paper plant, 50% mixed with plastic waste resulted from prior recycling activities. The main part of this research activity has been focused upon the burning process technology of the industrial waste by CFD analysis in order to reduce the variation range of operational parameters’ values and to estimate the possibilities of dangerous emissions to occur. Working upon an existent 1 MWt solid fuel pilot furnace, a geometrical model has been constructed, meshed and then solved to produce information concerning the burning process and its dynamics. A chemical mechanism has been adopted from literature, to predict the kinetic chemical process inside the flame. The principal contributions of this research is to create a thermal treatment for the primary solid waste, capable to be realized inside an industrial installation at a competitive cost, to produce energy at the same time with tamping the waste at a high degree, to create the possibilities for an easy metal pieces separation and not to produce pollutant emissions. Keywords: industrial waste, plastic waste, incineration, CFD analysis, waste co-combustion

Abstract: Due to the required high demands of quality products and to higher productivity rates, automated inspection systems have to be implemented in the industry. These inspection systems have to be reliable, fast, robust and flexible in their functionality in order to meet the high demands of the industry. An X-ray image of the product is taken and analysed by the system. The most important stages of the inspection process are the segmentation of the image into meaningful objects and the consequent analysis of these. This paper presents a Competitive Hopfield Neural Network (CHNN) for the segmentation of dual-band X-ray images of inspected product and a high-level detection of foreign bodies/defects based on fuzzy logic. Keywords: composite materials, image segmentation, Hopfield neural network, dual-band image, X-ray image, fuzzy logic

Abstract: It was considered as contamination, the carbonyl growing in the primary and secondary polyolefins blends and as effects of contamination, the degradation rate increasing, the induction period and the service life diminishing of the products molded from these blends. Using the carbonyl time variation during the first life, it is possible to estimate, for a given contamination, the degradation rate, the induction period and the product service life molded from polyolefins post consumers goods and so the optimal solution for the polyolefins mechanical recycling. Keywords: Mechanical recycling, secondary polyolefins, mathematical model, contamination