Browse Articles

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

The paper presents definitions of the main kind of mesogenic groups recognized by IUPAC. For a better understanding of the terms, for every type of mesogen, we attached a structure or picture. Keywords: liquid crystals, mesogenic group

This work presents the study of the pyrolysis process of polysilane preceramic precursors. This study stated that the yield in ceramic material is influenced by the heating rate and depends on the chemical structure and polydipersity index of the polysilane. Therefore, the yield in ceramic material is improved when the polymeric precursor has a high content in thermal unstable groups, a narrow molecular weight distribution and a low content in linear and cyclic oligomers. Keywords: thermal behaviour; polysilane precursor; ceramic material

In situ via anionic ring¡Vopening polymerization of epsilon¡Vcaprolactam in the presence of bronze microparticles was promoted as a route for the synthesis of nylon 6/bronze composites by rotational molding. The process was performed at 160 oC well below the melting temperature of the nylon 6 (Tm~225 oC) and initiated/activated with ethyl magnesium bromide/N,N¡¦¡Visophthaloyl¡Vbis¡Vepsilon¡Vcaprolactam system. The experimental data demonstrated that the physical and mechanical properties of polyamide 6/bronze composites depend on the filler concentration. Keywords: anionic polymerization; epsilon¡Vcaprolactam; polyamide 6/bronze composites, rotational molding

The article presents a study for water vapours permeability and diffusion properties for two hydrophilic materials, used for soft contact lens manufacturing. The materials have been investigated according to DIN 52615, German Standard. The technological advances in obtaining new hydrophilic materials presume a better biocompatibility of these materials and the comfort of the patient. In this way, our study advances an investigation for the microporous hydrophilic materials, to compare their functional properties. Keywords: water vapours permeability, diffusion properties, hydrophilic materials

Some organosilicone monomers with -CHO functional groups were synthesized by a condensation reaction between the methyl- or phenyl-chlorosilanes and an aromatic aldehyde. The products were characterized by IR and 1H-NMR spectroscopy, elemental analyses, melting points. Keywords: chlorosilanes, organosilane, aromatic aldehydes, functional groups

The paper defines the notion of charge space whose study is very important for the improvement of the characteristics of the polymeric electroinsulated materials. The latest nondistructive methods used for the determination of ions improvement are described, insisting on the information obtained in polymers by using them. The interfacial phenomena in the mica-epoxide-novolac compound are studied, used as isolation for copper bars in alternative current generators, focussing on the variation of the electrical characteristics of the material with temperature and frequency. Keywords: charge space, electrical characteristics, temperature, frequency