Browse Articles

This work presents the results regarding the formation of charge clouds due to the oil movement through non-conductive plastic and glass pipes . We have analzsed the equations that depict the charge distribution, the measurement of electrical charges and their effects on plastic and glass pipes in the transport of oil products . Keywords: plastic pipes, a non-destructive test, oil, diffusion, migration and load conversion.

Some new iron (II)-polymer complex structures having siloxane units included either in ligand structure or as co-monomer partner with an already metal (Fe2+) complexed structure were prepared and characterized by the spectral and elemental analysis. Solubility tests and viscosity measurements have also been performed. Keywords: siloxane, iron complexes, azomethine, ferrocene

Using the well known Wurtz coupling technique in heterogenous system, polyhydrosilanes copolymers with diphenyl sequences were synthesized. This work describes the possibility to maintain stable Si-H group and to obtain functional polysilanes. Also, the poysilane copolymer with reactive Si-H side groups was obtained through a homogenous coupling reaction of dichlorodiphenylsilane with dichloromethylsilane. The reaction was carried out in a tetrahydrofurane solution of sodium-potassium alloy complex with 18-crown-6 with a well defined composition of alkali metal ion pairs (Mt+/ crown ether, Mt - ) at –75 0C. The results were compared with those obtained by the heterogenous coupling reaction of the same monomers. Keywords: polyhydrosilane, Wurtz heterogenous coupling, homogenous, crown

This paper presents the possibilities of creating weldings for various products made of inteligent composite materials. The acoustical parameters and their influence on the quality of the weldings are analysed from the large domain of technological, mechanical and acoustical parameters of the welding process. Furthermore, the authors present the welding process of an inteligent car stop. Keywords: inteligent composite materials, welding, acousticals parameters

This paper presents experimental results on tribological behaviour of some composites with PTFE matrix under water lubrication. The experimental work pointed out particular processes taking place in the superficial layers of the tested composites. The results were plotted in order to underline the existence of an optimal regime for a system with given geometry, materials and lubrication conditions. The composites with PTFE matrix have an optimal composition as concerning the adding materials concentration that gives better tribologiocal behaviour, including low friction coefficient and wear. For instance the composites with PTFE matrix and glass fibber have this optimal concentration range of 10…30%. There are presented maps for these two tribological parameters in order to reveal the importance of the sliding regime parameters as normal force and the sliding speed. The tests also underline that water lubrication could be o solution for sliding bearing taking into account the interest of scientists for environment protection. Keywords: tribological behaviour, composites , glass fibber, water lubrication

The paper presents the international trends in the use of PEHD pipes considering losses in the distribution pipeline. It also presents elements imposed by the quality assurance conditions, from the PEHD welded pipes execution point of view, of welding technology homologation according to PT ISCIR CR 21-1999, of verification and certification of welders who make such welded joints according to EN 13067 Keywords: PEHD, distribution pipes, welded joints

The efficiency of a company’s activity can be estimated as referring to permanently updated BAT references. As a general rule, according to this quantifying system, the waste reduction at the enterprise level is a must. In Romania this methodology is poorly known and even less operational. Due to the European environmental legislative system this kind of waste reduction algorithms becomes more and more necessary for an enterprise survival on the market. This paper presents such a methodology, illustrated by a case study. Using a flow simulation, an optimized design for this system is described. Keywords: monitoring system, modelling and simulation, optimization, environment

The high values of the penetration and of the ring and ball softening point of the distillation road bitumen are determined by the absence from its composition of the high molecular weight fraction, solved in this medium. The effect of the modification of the distillation bitumen with additives designed for decreasing the penetration, on all the bitumen properties is presented. The low density polyethylene determines a drastic diminishing of the distillation road bitumen penetration and an important increasing of its softening point. This polymer is very well dispersed in the bitumen matrix, where it is possible to be solved. Keywords: distillation bitumen, polymer modified bitumen

The paper develops a method based on the thermal effects caused by pressure drop, internal friction, external friction and convection, for polymer melts pressure drop calculation in non isothermal melt flow through the channels. The whole thermal effect is equivalent with a supplementary pressure drop Dp (T). Later on Dp (T) generates a supplementary length L (T). This value is added to the initial channel length and an equivalent length, taking into account the thermal effects, Lech , is obtained. By substitution of the length L in isothermal pressure drop relation, with length Lech, the new relations may be applied for non isothermal flow melts. The equivalent length concept is applied to a real case. Keywords: nonisothermal polymer flow, rheology, polymer mold design, polymer melts pressure drop

Formaldehyde resins containing resin acid derivatives in their structure were synthesized. The insertion of resin acid derivatives into molecular chains was carried out to improve the cohesive strength of pressure sensitive adhesives. IR, 1H-NMR spectroscopy and other methods were used to characterize the monomers and polymers. The presence of the hydrophenanthrene moieties in the chemical structure of these polymers confer them, high solubility in common organic solvents, high adhesiveness, hydrophobicity and water resistance. The presence of formaldehyde resins with hydrophenanthrene moieties (up to 10 wt-% referred to the adhesive composition) into pressure sensitive formulation offer them high increase of cohesive strength without affecting the adhesive strength. Keywords: formaldehyde resins, hydrophenanthrene moieties