Browse Articles

In this study a series of urethane prepolymers based on diisocyanates (diphenylmethane diisocyanate – MDI, toluene diisocyanate – TDI), castor-oil and filler from bronze aluminum and bitumen in methylene chloride as solvent was synthesized for corrosive protection of equipments utilized in nonferrous ore industry. The polymers were tested to work, for a period, after which the materials were analyzed to see how they resisted in corrosive medium. In ore industry, the corrosion of equipment utilized is both an electrochemical and physical (abrasion) process. In the form of a liquid spray coating, the polyurethane elastomer is especially useful for protecting industrial ore equipments, adding years of service to surfaces that would otherwise suffer from wear and corrosion. The polyurethane coatings have been characterized by means of TEM, TGA, 1H-NMR and IR spectroscopy, and stress-strain measurements. The hardness measurements were effected on disc with a standardized apparatus in grade Shore A (oSh A). Keywords: polyurethane elastomer, coating, corrosive protection

The delivery pharmacokinetics of the codeine, which was entrapped in some polymeric matrices, was studied. As matrices, the methyl methacrylate homopolymer and methyl methacrylate copolymers with different percentage of 2, 3 epoxypropyl methacrylate were used. The release profile is correlated with the nature and obtaining manner of the macromolecular structures with and without the presence of a continuous electromagnetic field respectively. Keywords: crosslinked, functionalised copolymers, codeine, drug release, release rate

The present paper deal with a less known subject from the unconventional technologies namely the fluid flow through a working zone situated between the tool and workpiece electrodes. One take into account the possible types of flow, one establish the mathematical model of the flow and based on this model one determine the process parameters and their influence on the fluid behavior during the process. One present some experimental results for the EDMUS process which confirm the concordance between the theoretical model and the experimental values of the rheological parameters. Key words: electrical discharge, shear stress, shear speed, dielectric liquid

Plasticulture is a system of growingcrops in a way so that a significant benefit is derived from using plastic polymers. We have obtained a threeyer polymeric foil with photoselective additives in order to modificate the microclimate. This foil was subjected to an experiment by covering high tunnels with tobacco culture. We have reported about optical and mechanical properties of this foil, before and after the experiment and the influence on tobacco culture. Keywords: plasticulture, polymeric foil, co-extraction, multilayer film, solar radiation

The relationship for the calculus of flow in a single screw extruder was inferred based on the analysis of the real movement of the powder material in the feeding zone, considering the screw rotating and the barrel stationary. The relationship is applicable to extruders with the barrel in the feeding zone both smooth and grooved. Both the slipping of the powder material with respect to the surface of the screw and the existence of a velocity profile on the depth of the powder layer were taken into consideration when establishing the flow relationship. The fundamental hypotheses of the new theory are: - barrel stationary and screw rotating; - in the powder layer, powder particles have a relative motion. The relationship for the direct calculus of the deviation angle b was deduced. From the analysis of the results obtained applying the relationship for flow, where the flow factor can be calculated with the relationships in the paper, one would notice that the flow will grow both with increasing the depth of the channel in the feeding zone and the increase of the friction coefficient between the powder material and barrel,, as well as the one between the powder material and screw. Keywords: extrusion, optimization, flow factor, deviation angle

The present work investigates the possibility to control the alcoholysis reaction in order to obtain various sorts of polyvinyl alcohol with a predetermined degree of alcoholysis and high block copolymer character. On this purpose, two methods are suggested: quantitative determination of methyl acetate (resulted as a by product of the alcoholysis reaction) existing at a certain time in the system, and termination of the alcoholysis reaction according to a predetermined calibration curve. Keywords: Polyvinyl alcohol, polyvinyl acetate

Grease degradation has an important influence concerning vibration level of ball bearings in running time. Resulted sediments after chemical and thermic degradation process alter frequency spectrum, similar with waves on inner and outer races. Unlike with these, the alters bring about sediments that appear and disappear in running time. So, they adhere or detach from race ways. Acquired signals analysis give more details about estimation of ball bearings grease life reserve. Keywords: lubrication, grease, ball bearing, vibration

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