Browse Articles

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

This paper presents some considerations about influences of the milling process on the quality of plastic materials in the process of recycling. There are presented the advantage and disadvantage of the use of the proposed milling system, economic and serial implications. Special part is destined on the technologies processes, granulometric analyze and equipment. Keywords: plastics recycling, raw materials, milling, granulometric analysis, quality, optimization, environment

In this paper are comparatively presented a few characteristics of some indigenous distillation and oxidation road bitumens. Some differences between these two bitumen types are put into evidence, some of them being of importance in the case of the modification using polymers. The distillation bitumens exhibit the greatest deviation of penetration values by comparison with the assessed standard values for road bitumens. For this reason, this bitumen was modified by addition of an indenic resin. Consequently, the modified bitumen shows an increased value of the “ring and ball” softening point, a decreasing of penetration index and an enhancement of the elastic properties. Based on the experimental data, a content of 5-10% indenic resin was found having a positive effect on the studied distillation bitumen. Keywords: road bitumen, oxidation bitumen, distillation bitumen, indenic resin

In order to test the presence of some chemical substances within the composition of specific liquids and fluids, such as cosmetics, beverages, hydraulic oil, it is absolutely necessary to measure the foam level as a quality condition for selling them on the market. The paper deals with designing an original device for measuring the foam level, which has the following main components: a mechanical subassembly for positioning the sensors, a closed volume with a propeller subassembly for mixing the liquid and the PC controller. We recommend the use of Thermo-Russel sensors, taking into account the accuracy of the final results. Electrical micro actuators, such as brushless electrical micromotors, are used for actuating the mechanical components. The designed device may have the following original features: the electro-mechanical positioning system for sensors and propeller in the way regarding the increasing of the positioning accuracy of the sensors; the possibility of having different rotational speed of the propeller, as function of liquid viscosity. Taking into account that the foam level could be rapidly destroyed, so that the process time should be over 0.1 s, the device might be controlled either by microcontrollers or by a PC with data acquisition boards. Knowing that the creep of the propeller is altering the measuring final results by reducing the speed of the liquid, the paper presents the tridimensional model of the propeller and its translational displacements using the finite elemet method. Keywords: modelling, simulation, generating wet foam into liquids, measurement

During the past decade, a lot of effort has been spent to develop strategies to mitigate the damaging effects of earthquakes. This work has been directed at both civil structures and nuclear facilities. Polyurethane elastomers (PEs) based on polyethylene adipate diols and aliphatic diisocyanates can be used as passive isolation bearings in buildings applications. In the present study, polyesterdiol and 1,6-hexamethylene diisocyanate (HDI) have been used in polyurethanes, using glycerine, ethylene or diethylene glycols as chain extenders. Effect of varying the concentrations of diisocyanates and structure of chain extenders on PEs has been discussed with reference to mechanical properties. IR and thermal analysis techniques (TGA) were used for characterization. The results reveal that aliphatic character of diisocyanates lowers the temperature required to achieve the flexibility in the polymer. Based on their mechanical properties, PEs have great potential for applications where wind and earthquake loads resistance, dynamic-to-static stiffness ratio and vertical and lateral load characteristics are required. Keywords: aliphatic diisocyanates, passive isolation, chain extenders