Browse Articles

This paper deals with the ethylene-propylene-terpolymer rubber (EPDM) crosslinking and grafting by use of accelerated electrons (AE) beams in the presence of a multipurpose monomer such as trimethylolpropane-trimethacrylate (TMPT). Physico-mechanical characteristics of the samples irradiated with various AE doses were compared with those of the sample obtained by classical crosslinking in the presence of peroxides. The resulting data were subjected to processing and statistical analysis to show the reliability of the EPDM crosslinking and grafting by means of AE. Based on the experimental data, the single factorial regression models for the assessment with a 95 % probability of rubber blend characteristics with different irradiation doses were established. Keywords: EPDM, crosslinking, radiations, regression model, estimation of variables

Molecular dynamics is one of the methods used now-a-days by the scientific community to study the property of polymers. This paper presents a new method for multiscaling molecular dynamics that combines the advantages of fine-grained and coarse grained representations. The new methodology is implemented in the package Gromacs for molecular dynamics, a world-wide used software that achieves the best performance on single processors. The article presents the methodology, its implementation in the Gromacs package for molecular simulation and performance results. Keywords: polymers, molecular dynamics, Gromacs, multiscaling modeling

This paper presents the influence of the processing temperatures on the physico - mechanical properties of polyamides (PA) used in injection molding of high performance sport products. The samples were obtained by processing PA at the following temperatures: 270, 285, 300, 315, 330 and 345°C. It was established that the pressure in the mold decrease as the processing temperature rise. Further, thermal analyses were performed (TG, DSC, and DMA) and it was noticed that the processing temperature had an influence on the thermal stability of the polymer, but the glass transition temperatures (Tv) and melt temperatures (Tt) were poorly influenced by the processing temperature. Keywords: polyamide, injection molding, TG, DSC, DMA

Polymeric composites are widely used materials in very complex parts, because of their special characteristics. There are theoretical relationships which can be used in predicting a composite material characteristic values (stress, elasticity modulus, elongation etc) but, reality proved that these relations are not so accurate. So, determining real values of polymeric composite material important mechanical characteristics is essential for parts exploitation resistance and reliability calculi. This paper presents experimental and theoretical studies for determining a random reinforced glass fiber polymeric composite material mechanical characteristics, pointing out the importance of knowing real values of these characteristics in parts designing. The obtained results are, also, confirmed by statistical data processing while, importance of the involved studies is evidenced by a case study finite element ANSYS simulation. Keywords: polymeric matrix, reinforcing element, glass fibers, composite, mechanical characteristics

Dynamic complex phenomena due to specific running conditions for textile spindles such as speeds, unbalanced yarn bobbins, their attachement to the ring frame, types of spindle bearing units, are the main causes of significant modification in time for running parameters with important implications in unwished efect appearance. In this way, the paper presents some aspects concerning the oil viscosity influence both on rotative spindle+yarn bobbin system dynamic response with the help of double amplitude measuring for spindle rod and on running power consumption of textile spindles. The experimental researches make evidence on textile spindles vibration amplitudes increasing with oil viscosity decreasing, but power consumption increasing in corellation with oil viscosity increasing too; these aspects have a negative influence on running dynamic stability. The experimental results presented as influence diagrams contribute to establish an important data base which will help in taking adequate decisions for oil viscosity selection necessary to textile spindles. Keywords: oil, viscosity, textile spindle, dynamic response, power consumption

In this paper we present the result of the experiments performed to obtain the characteristics curves for five composite materials with random distribution of reinforcement. From these curves we determined the elasticity modulus and the resistance to fracture. Using the modal identification method we determined the first eight eigenmodes for two bars from composite materials (Bar 1 – phenolic fireproof resin reinforced with fiberglass; Bar 2 – ortophtalic polyesteric resin reinforced with fiberglass), embedded at one end and free at the other. We determined the eigenpulsations for the modes considered and we used the first four modes for the calculus of elasticity modulus. The results obtained by traction testing compared with the one from modal identification method certify the utilization of modal analysis in the determination of properties of composite structures. Keywords: composite materials, elasticity modulus, modal identification method

The actual tendencies of the European market of metallic component parts for auto vehicles impose the utilization of materials that lead to the increase of the products reliability and their framing into the matrix cost-quality imposed by the big European producers [4, 9, 11, 14]. The covering of the quaternary alloys based on copper with polyester is inscribed among the technological procedures that aim at the improvement of the performances of the metallic parts of the auto vehicles with a view to reducing the percentage of out of operation and decreasing the maintenance and service expenses, having as final purpose the increase of the competitiveness on an European market being in a strong competition. The present work spotlights the positive influence of the covering of the quaternary alloys CuNiAlSi with polyester impregnated with 10% graphite on the main mechanical characteristics, especially of the wearing resistance that has a direct effect on the increase of the functioning time in the total life cycle of the product. Keywords: polyester graphite quaternary alloys

There were studied six variants of type suspension gels with 1.5% propiconazole nitrate, with various ointment bases: 4% hydroxypropyl cellulose (HPC-H), polyethylene glycol modified base and hydrated cetylic alcohol base, using as wetting agent and permeation enhancer glycerol as well as propylene glycol. The aim of this research is the physico-chemical characterization of gels: aspect, pH, homogeneity, rheological behaviour, viscosity and antifungal activity. The formulas based on HPC-H 4% have a plastic behaviour and an increased yield value; the formula sbased on modified PEG are rheopectic type, having a higher degree of thixotropy generated by propylene glycol. The formulae on hydrated cetylic alcohol base have a thixotrope behaviour (the formula including glycerol as wetting agent) and respectively thixotrope – antithixotrope behaviour (the formula including propylene glycol). The values of viscosity are higher in case of gel formulas having propylene glycol as wetting agent. Propiconazole nitrate has a good antifungal activity against clinical isolates of Candida spp., including strains resistant to other antifungal agents. All tested propiconazole nitrate gels have similar activity against Candida spp. Keywords: propiconazole nitate, gels, rheological behaviour, antifungal activity

The paper presents the results of a combined numerical and experimental study for validation of a new three-dimensional specialized finite element, used for modelling the behaviour of laminated composite materials, reinforced with fibers. First, the stress and strain state in a circular plate loaded with an uniformly distributed force and fixed on the contour is evaluated using the proposed finite element. Two types of laminated composites are considered, in order to test the behaviour of the proposed element and the models conceived for calculus of laminated composites having different structures. To validate the new element, calculations were made also using the finite element code ANSYS-11. In the second part, the results of an experimental study on the behavior of plates made of the considered laminated composites are presented and compared with the previous numerical ones. The good agreement between the obtained data showed that the new proposed element is adequate for modelling the bending behaviour of fiber reinforced multilayer composite materials. Keywords:specialized finite element, laminated, composite, fibres, validation

The influences of the concentration of the Pekoflam DPN 1 (active flame retardant reagent), of the cure temperature, of the neutralization efficiency and of the samples final washing after the flame retardant treatment have been studied. By using the analysis of variances there has been proved that all studied factors have significative influences on the length of the carbonization area, on the rate of spread of the flame and on the weight increasing after the flame retardant treatment. Keywords: efficiency, flame retardant reagent, pad-dry-cure technology