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A polyurethane (PU) based on 4,4’diphenylmethane diisocyanate (MDI), copolyester poly(ethyleneadipate) diol (PEA) and extended with butylene glycol (BG) was synthesized via a two steps polymerization technique. The thermal stability of the PU was investigated by thermogravimetric analysis (TG) at temperatures between 30 and 600oC. The synthesized PU was irradiated in an UV exposure unit as such the spectral distribution of the light was a good match for terrestrial solar radiation (200 h, l > 300 nm, Ia = 30 mW cm-2). The modifications in the chemical structures of the PU before and after irradiation were characterized using Fourier transform infrared spectroscopy - attenuated total reflectance (FTIR-ATR) technique. The yellowing index variation (YI) exhibited a systematic trend increase with irradiation time. Our results are in agreement with the formation of quinoide structures, which are colored products resulting from photo-degradation of PU. Keywords: polyurethane, thermal analysis, photostability, thermal stability

In this study, blends of biodegradable matrix as poly(3-hydroxybutyrate) (PHB) and fibers provided by renewable resources were prepared by a melt blending method. Improvement of the compatibility between fibers and polymer was studied using coupling agents: maleic anhydride (MA) respectively, succinic anhydride (SA). Mixtures with two types of fibers were investigated in terms of microscopy, torque, density, tensile strength, melting temperature and contact angle. It is found that the mechanical properties of PHB with cellulose fibers blends were better than PHB and wood fibers. Keywords: polyhydroxybuthyrate, wood fiber, cellulose fiber, coupling agent, blend

When the plastic materials products are obtained by injection into the mould, the fluid plastic mass takes the shape of the cavity and then, in a technological time, the obtained product cools until a temperature which makes possible its unloading without any deformation. Each product or more products may be realized during a period which means the time of one manufacturing cycle. An optimum manufacturing process is a continuous process without waiting times. The paper presents a methodology for the calculation and adjustment of some injection parameters which influence the time of one manufacturing cycle for the plastic materials products realizing. Keywords: plastic materials manufacturing, thermal processes of the polymers injection

This research studies the influence of scratches on the polyethylene gas pipes after squeezing with the squeeze-off tool in order to stop gas flow due to an intervention of the gas pipeline. Problem occurs when there is a need to make a decision whether it is safe to squeeze the pipe with scratches. The goal of the research is to determine the change in the depth of scratches on the polyethylene gas pipe after squeezing with the squeeze-off tool. After the experimental research it was determined that there would be a change in the depth of scratch. The change of the depth of scratch positioned on the squeeze-off ear would be considerably bigger when compared to the depth change of a scratch positioned under the upper cylinder of the squeeze-off tool. Based on the resulting data, it is a recommendation of the author not to squeeze the pipe if it has scratches. If the squeezing if inevitable on the place where there is a scratch, the squeeze-off tool needs to be positioned under the upper cylinder of the squeeze-off tool. Keywords: scratches, polyethylene gas pipes, gas flow,the squeezing

A series of phosphorus-containing polyesterimides has been synthesized by solution polycondensation reaction of an aromatic dianhydride, namely 1,4-[2-(6-oxido-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl)]-naphthalene-bis(trimellitate)dianhydride, with various aromatic diamines. The polymers were easily soluble in polar organic solvents, such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, tetrahydrofuran and chloroform. They showed high thermal stability, the decomposition temperature being above 400oC and the glass transition in the temperature range of 174-194oC. Due to the presence of phosphorus the polymers gave high char yield in thermogravimetric analysis. Solutions of the polymers in N,N-dimethylacetamide showed photoluminescence in the blue region. Keywords: polyesterimides, phosphorus-containing polymers, good solubility, thermal properties, photoluminescence

The new organic coatings were realised from polyurethane resin and alkyd+melamine-formaldehyde resins. The electrochemical techniques of the electrochemical impedance spectroscopy (EIS), cyclic potentiodynamic polarisation and linear polarisation were applied and the tests were carried out in a normal aerated 3% NaCl solution at ambient temperature. Also, open circuit potentials in 3% NaCl solution were monitored for 300 immersion hours. Salt spray tests were carried out according to ASTM B117 Standard. An electric equivalent circuit with two time constants representing the barrier characteristics of the intact organic coating, and the corrosion process occurring at the substrate/paint interface was fitted. The both coatings revealed very good protective properties, assuring a very good resistance for about 8 years in the ambient environment. Keywords: protective films, immersion tests, salt spray tests, EIS, cyclic polarisation

Due to the multitude of restorative materials on the today market, the studies presented in this paper come to make some contributions regarding the evaluation of biomaterials in terms of resistance to the wear process, the factors influencing the tribological behaviour of hard structures and restorative dental biomaterials in the oral environment. Keywords: composite materials, tribology, wear, dental medicine

In the idea of improving the performances of both full and removable partial dentures, new materials and technologies are coming on the market, promising a better quality. Thermoplastic materials are used more and more widely in the technology of complete or removable partial dentures due to their superior qualities. Thermoplastic resins are suitable for manufacturing a wide range of removable partial dentures without metallic structure, in optimal conditions of biocompatibility. By injection, we have manufactured several removable partial dentures without metallic structure. 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: removable partial dentures, thermoplastic materials, molding-injection devices, casting, full dentures, errors

The paper is focused on the behavioural simulation of the intraocular organic lenses, defined by geometric characteristics (the accumulation radius, thickness and diameter) [1] and material characteristics, for a certain incident wavelength [2]. The simulation provides a picture of the ray-tracing for the second and third reflection/refraction. At the same time, the user can display the print of a ray on a normal plane related to optical axis direction. The authors designed the simulation program, aimed to evaluate the wounded through the multiple reflections in the spectre available for chosen material. Thus the disparity of a certain parameter will influence the transference through lenses for some radiation or spectre. The paper is designed to be used in optics, to shape the refractive components, and can predict the useful diameter of lenses, diaphragms or aperture stop. Keywords: organic optical glass, optical layout, multiple reflections, imaging

In order to point out the intrinsic peculiarities of thermorheodynamical behaviour of solid-like polymer materials, the framework of a Zener - Arrhenius model is considered, the frequency or/and temperature dependences being approached in the case of strain-controlled conditions. The complete set of the explicit general relations providing the characteristic thermorheodynamical quantities (the storage, loss and absolute moduli, as well as the loss factor, and the corresponding storage, loss and absolute compliances) is presented in terms of meaningful rheological parameters including the low - and high frequency limit values of the storage modulus, and the appropriate relaxation time. The underlying analytical relations are given in forms suitable for direct numerical simulation of both isothermal frequency - dependence, and well as of isochronal temperature - dependence circumstances. Keywords: analytical relations, characteristic thermorheodynamical quantities, strain-controlled conditions, Zener - Arrhenius model, isothermal and isochronal circumstances