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By skilful combination between polythiophene backbones and poly(ethylene glycol) (PEG) side chains of different lengths, amphiphilic, fluorescent copolymers having branched architecture of “hairy rods” type were obtained by Suzuki polycondensation. Their structural characterization was performed by 1H-NMR, 13C-NMR and FT-IR spectroscopies and thermal behaviour was followed by differential scanning calorimetry (DSC) and thermogravimetrical analysis (TGA). Photophysical properties in aqueous solutions were evaluated using UV-Vis and fluorescence measurements. The amphiphilic nature of the synthesized polythiophenes and the presence of PEG side chains induced the self - dispersability in water, as well as the formation of fluorescent nanoparticles through self-assembling. The size of the nanoparticles in water was assessed by dynamic light scattering (DLS) and atomic force microscopy (AFM) investigations and the effect of incubation time on three cell lines viability was evaluated, as well. Keywords: polythiophenes, nanoparticles, Suzuki polycondensation, “hairy-rods”, self-assembling

Epoxy resin / carbon nanotubes (CNTs) nanocomposites are nowadays intensively studied in order to produce high performance materials with enhanced properties for specific applications in all activity fields, from electronics to automotive and aeronautics. In order to improve the interactions of CNTs with the polymer matrix, a functionalization of CNTs surface is often required. In this work, functionalized CNTs/epoxy nanocomposites were obtained and investigated by thermogravimetric analysis. Non-covalent functionalized CNTs with three types of surfactants were used. Activation energies of the degradation processes were calculated using Kissinger-Akahira-Sunose isoconversional method. The influence of surfactant type, functionalization mode (covalent or non-covalent) and functionalized CNTs content in composite on the activation energy as a function of the degradation conversion degree was studied. Keywords: thermal degradation, isoconversional method, carbon nanotubes

Necuron is a polyurethane material (PUR) that is used for various applications of industry. The use of these materials in industry increased in recent years because of their good mechanical and machinability properties. Good knowledge of the mechanical behaviour of these materials is highly important therefore this work presents the results of tensile tests carried out on four different types of Necuron. The twenty-eight specimens used were divided in two categories: one without defects and one with defects of two types. Results show that Necuron 1020 is the stiffest material, whereas Necuron 1300 is the strongest. Keywords: tensile testing, necuron, tensile strength, Young’s modulus

Base isolation systems are nowadays largely used to protect the build environment and to avoid loss of life. While the behaviour of natural rubber bearings NRB and lead rubber bearings LRB is well-known, hybrid devices incorporating a NRB and a LRB, due to their complex behaviour, are difficult to be modeled. The authors have developed a theoretical model able to describe with high accuracy the performance during earthquakes of hybrid isolation systems, meantime permitting to determine the equivalent stiffness for all levels of horizontal loads. At the end of the paper numerical simulations give an overview about the possibilities to control the structure response by fitting some parameters of the device. Finally comparison with the behaviour of “classical” devices is performed. Keywords: rubber, neoprene, composites, base isolation, earthquake

The development of resins represented a great step forward in dental technique, the first thermopolymerisable acrylic resins being developed in 1936. Due to their disadvantages, several new materials and their processing technologies, which promise better quality, were introduced on the market, among them diacrylic composite resins. Initially composites were elaborated as esthetic restorative materials, subsequently they developed very much, so nowadays are being used in many various fields of dentistry. Indications for diacrylic composite resins. (DCR) in dental technique include: esthetic veneering for mixed metal-polymeric fixed prosthetic restorations (FPR), unidental or temporary FPR, inlays, onlays, epitheses, repairing damaged porcelain veneers, artificial teeth, manufacturing the base of mobile and removable dentures, repairing and/or re-optimization of the mobile and removable dentures. The aim of this study is to bring into discussion the superior qualities of the the new generation, VITA VM LC (VITA) composite veneering resins. The laboratory steps to be followed in order to obtain a VITA VM LC veneered FPR are the usual ones. After completing the metallic frame, the following step is veneering with VITA VM LC. The VITA VM LC layering concept is oriented after the natural model and is clearly distinguishable from all the other stratification concepts. The natural fluorescence and opalescence reproduction possibility leads to individual results with an aesthetically impressive appearance. A layered restoration performed with VITA VM LC behaves like a natural tooth in different lighting conditions. The excellence in dentistry is often achieved by combining scientific principles with artistic creativity, while choosing the material and technique has a major importance. Keywords: diacrylic composite resin for veneering, VITA VM LC, layering concept, aesthetic results

Dielectric relaxation studies were carried out on unfilled and silica particle filled highly crosslinked PDMS samples, at temperatures above the calorimetric glass transition temperature. Our experiments suggest that the main a relaxation peak is preceded by a pre - a relaxation one, whose characteristics are not dependent in their nature on the presence of the reinforcing silica particles. This suggests that its presence may be characteristic of the high crosslink density PDMS. Keywords: highly crosslinked siloxane elastomers, silica filler, dielectric relaxation in the glass transition region, a-relaxation

Starting from the dynamic response of a sandwich beam with damping (which is in free vibration), is established a method used to determine the damping factor. We experimentally calculated the stiffness and damping factor per unit length and unit mass for beams with middle layer made of polystyrene and polypropylene honeycomb respectively; the external layers were made of epoxy resin reinforced with fiber-glass fabric and carbon-fiber fabric respectively. Keywords: sandwich beam, damping factor, polystyrene, polypropylene honeycomb, free vibrations

The dynamic behaviour of an orthotropic shaft leads to a nonlinear differential equation, Mathieu type, whose solving is quite difficult. Certain problems in theoretical physics lead to Mathieu equation, particularly the problem of the propagation of electromagnetic waves in a medium with a periodic structure, the problem of the electrons’ motion in a crystal lattice in the quantum theory of metals. The parametric equation was solved numerically for time history and was time integrated using Runge-Kutta method with initial boundary values. The results show a totally different dynamic behaviour of the shaft made of an orthotropic material compared with the one made of an isotropic material. Key-words: orthotropic material, shaft, orbit precession motion

It is a well-known fact that either pellets or granules used in sandblasting operations for cleaning/finishing metal surfaces of any kind, are subject over time to processes of either splitting or wear of the surface, thus diminishing their operational features, such as, for instance: the angularity and dimension. When being used in sandblasting operations, the granule size fractions that have lost their capacity of finishing surfaces are being sorted by sifting and eliminated. In industrial conditions, where very large surfaces are being sandblasted, the grit turns into a major problem, since it often requires large warehouse surface areas for storage. In that sense, this paperwork presents experimental data regarding the worn grit fractions management by using it in asphalt mixtures, conferring, beside an economic benefit, also that of environment protection, since those lightweight fractions oftentimes form very polluting air floating powder. By eliminating those fractions that are reusable in the process of sandblasting, on the remaining sort resulted from sifting through the 1.0 mm strainer granulation and bitumen behaviour studies were carried out. The analysis of proposed asphalt mixtures, holding a certain percentage of grit, highlighted the fact that the latter, by both the 0.4- 0.1 mm granule size and by the floatable particles of less than 0.2 mm granule size, allow for the replacement of natural quartz sand. The physical-mechanical features of studied mixtures were established on cylindrical probes made of bitumen, in which smashed silicone stone chippings were mixed, within standard required range of granule size, crushing sand and worn grit, in very well controlled mixing proportions. the results were compared to those derived from standard samples made of solely quartz crushing sand, alongside the other components that make up type BA8 asphalt mixtures, of a mere 6.5% bitumen of a 50/70 proportion, according to local standards. By comparing the two asphalt mixture type features (standard and experimental), it allowed for highlighting that worn grit may be very successfully used instead of crushed sand. Keywords: grit, asphalt mixture, recycling, exploitation, environmental protection