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The paper presents the research carried out by our team on achieving amphiphilic polymeric microcomposites, colored in ruby and violet shades for natural fibers dyeing (cotton, wool). The colored polymeric microcomposites were characterized in term of their morpholo- gical (by optical microscopy and SEM analysis) and physicochemical performancies (by FT-IR and UV-Vis spectroscopy, colorimetric analysis). The colored microcapsules were tested by studying the controlled release of the encapsulated dyes in water, to pH variation. This study was necessary to the coloristic characterization of colored polymeric microcomposites to determine the optimal microcapsules dye concentration and dyeing concentration of natural fibers.

In the paper it is presented a new Euler – Bernoulli theory based on an assymetrical distribution of strains towards the median plane, the area subjected to compression has a transversal stretching, while the area subjected to tensile has a transversal contraction. This theory takes into account the transversal contraction factors and consequently the eigenpulsations of bars vibrations with rectangular section depend on the ratio between the bars width and thickness. This theory is experimentally verified for Dammar based composite bars reinforced with cotton, flax, silk and hemp fibers. For the considered bars, we have experimentally determined the eigen frequencies and the damping factor values.

The selective collection of plastic, paper, glass and metal waste represents a desirable behavior in any civilized community with environmental concerns. The collection and recovery of recyclable materials is also a concern for the city of Arad, the purpose of this study being that of identifying the strengths and weaknesses of selective waste collection at the level of this urban community. Starting from the premise that responsible behavior in terms of waste and its collection is an important factor in the ecological development of a community, the present article aims to explore the local realities in this regard, to diagnose the state of things, as it is at present, in the city of Arad. We have highlighted and recorded the population’s existing mentalities and perceptions, the citizens’ expectations from the local authorities, in order to provide optimal intervention opportunities to increase control for a better management of selective collection.

In the paper, are studied the effects of three acids (sulfuric, nitric and hydrochloric) in concentrations of 10% and 20% on the composite materials (type resins reinforced with fiberglass). These composite materials are obtained manually and lends itself to getting various containers (for water for example), but can be obtained containers for temporary storage of acids. Certain composite materials with various combinations of fiberglass with a precise number of layers can be used for temporary storage of acids as a result of experimental research made in these paper are also given.

Polymeric bio-composites have special characteristics and use in various areas such as: automotive, aviation and aeronautic industries, civil engineering and for medical devices manufacturing. This paper presents the evaluation of impact behaviour of some types of materials suitable for orthopaedic use. As composites behave very differently at different rates of loading, static strength tests cannot be used to predict impact behaviour in the perspective of prosthetic medical devices study and manufacture. The used testing machine is Instron Dynatup Impact System with Data Acquisition and Control, model 8200, with assisted system of data acquisition and control.

The Pelton turbines convert hydraulic energy into mechanical energy, through the Pelton runner, by using high heads and small discharges. The runner has a complex geometry, described in drawings by transversal and longitudinal sections that form continuous surfaces. The SolidWorks software was used to design two Pelton runners: the R1 runner with 21 buckets and the R2 runner with 19 buckets. The runners were made of polymeric materials through the Rapid Prototyping process, using the Objet Desktop 3D printer, which is based on the Objet PolyJet technology, with a layer thickness of 28 microns [1]. The runners were used to measure the hydrodynamic characteristics of a Pelton microturbine on a test rig. The paper aims to highlight the advantages of the Rapid Prototyping process compared to the traditional technology used to manufacture Pelton runners that are intended for experimental research.

Polyethylene (PE) insulations have a wide applicability in the insulation of both underground pipelines and underground power cables. In this context, by coupled techniques of thermal analysis (TG/DTG+DTA) and microbiological determinations, have been studied thermooxidability and resistance to moulds action of some polyethylene sorts. Following the processing of the experimental data obtained by thermal analysis it was found that during the applied heat treatment (100 oC), in the first approx. 380 h, there is a growth of LDPE (low density polyethylene) polymerization degree by elongation of the aliphatic chains, after which the predominant process consists in the structure crosslinking. For MDPE (mean density polyethylene) samples, during the thermal treatment applied, it was found that the crosslinking degree of polyethylene (PE) increased without significant molecular weight change (with all the related consequences of increasing the weight of the tertiary and quaternary carbon atoms in the molecule). Microbiological determinations have highlighted that the resistance to filamentous fungal action of LPDE is higher than that of the investigated MDPE. It was found that after heat treatment applied (1000 h & 100 oC), both at LDPE and at MDPE, decreases the resistance to moulds action is decreased. It has also been found that moulds action resistance is substantially decreased when inoculated culture media and PE samples are exposed to an alternative electric field of 50 Hz – 6 Vrms/cm.

This paper presents the influence of the grinding percentage on some electrical properties, when the process of injection is used in the production of technical commodities, made of polyamide 6.6 (PA 6.6), polyoxymethylene (POM) and acrylonitrile butadiene styrene (ABS), for different industries. The specimens produced had the following compositions: new material 100%, new material 80% + grinding 20%, new material 60% + grinding 40%, new material 40% + grinding 60%, new material 20% + grinding 80% and 100% grinding. The measurement of the electrical properties was carried out using the methods for the determination of relative permittivity and of the dielectric dissipation factor, with the method of zero by Schering bridge. It was found that increasing the percentage of grinding in samples, from 0% to 100%, determined a slight increase in the values of relative permittivity at all three polymers tested and the increase of measurement frequencies for acrylonitrile butadiene styrene and polyoxymethylene led to insignificant changes in the values of relative permittivity, while in the case of polyamide, increasing the measurement frequency led to a slight decrease in the values of relative permittivity. It was also found that increasing the proportion of grinding in the specimens, from 0% to 100%, determined a slight increase in the values of the dielectric dissipation factor in the case of polyamide and polyoxymethylene, while in the case of acrylonitrile butadiene styrene increasing the percentage of grinding in the samples resulted in insignificant changes. The increase in the measurement frequencies for the three tested polymers resulted in a decrease in the values of the dielectric dissipation factor.

Extending of the welding application field by high frequency currents of the thermoplastic polymers requires the full knowledge of the physical parameters which characterize the joining process of the welded joint. Since these engineering materials are extremely sensitive to temperature variations, the present paper highlights the role of the thermal gradient in obtaining of some welded joints with high mechanical strength and free from continuity defects. Regarding this, it is demonstrated that increasing the thickness of the polyvinyl chloride films, from 0.4 to 1 mm, the heat effect in the contact area of the electrodes is kept and the welding process has a high stability. For a well-run welding process is obtained a uniform distribution of the molten material in the joint area with positive impact on the breaking force values.

Using the reliability accelerated tests in the early stage of solar cells life cycle, by using an high level of stress, in order to highlight the one or more degradation factors, on which could be quickly acquired a series of the experimental data, leads to point out the design errors of solar cells and to predictive assessment of reliability indicators. Environmental factors influence the lifetime of a solar cell. The action of each factors determines its aging and finally its degradation as the result of the combined action of sunlight, emissions, climate change, temperature and humidity, the action of dust, the saturated air from the proximity of oceans and seas, whose actions a solar cell undergoes during normal operation. In this paper has been analysed 10 polycrystalline solar cells subjected to accelerated corrosion tests. It has been also carried out two analyses, the first a quantitative analysis by determining the values of reliability indicators and the second one was a qualitative analysis of the degradation of polycrystalline solar cells using the optical microscope.