Browse Articles

The paper shows in its first part the role, efficiency, types, factors and mechanisms of using the synthetic polymeric flocculants in the paper industry. The experimental part shows the research carried out to determine comparatively the efficiency of using the single component retention systems, with micro/nano particles in the modern alkaline paper production compared to the conventional acid process. Keywords: paper, flocculation, retention aid, zeta potential, micro/nanoparticles

Mechanical properties of the new bromobutyl rubber-based composite (BrBR) were evaluated in comparison with similar NBC protection materials, used either in Romanian Army or in other NATO country armies. The following parameters were determined: mechanical strength, tensile strength and elongation, and the tear force – trouser-shaped test specimen. From the data obtained, a real improvement of the break parameters of BrBR, both in warp and in weft, versus the performances of Romanian materials in use was noticed. Also, versus the foreign materials, the material obtained presents properties basically between the French material and the German one. Keywords: NBC protection, composites, mustard gas, mechanical properties

Porous polysulfone (PSF) beads and composite beads (PSF-Cu-MT-Sil) obtained by incorporating copper-metallothionein functionalized silica in a polysulfone solution were prepared using the phase inversion method. Their characteristics were investigated with experiments of swelling, Fourier transform infrared (FTIR) spectroscopy and SEM microscopic analysis. Polysulfone and composite beads were used in catalase (CAT) immobilization. The kinetics of the biocatalytic process, stability under different temperature conditions and the inhibitors effect were studied as major factors on the immobilized catalase activity. The present work is meant to demonstrate the potential of crosslinked polysulfone and especially polysulfone with copper- metallothionein beads for the enzyme immobilization process. Keywords: polysulfone, composite beads, catalase, enzyme immobilization

Composite materials of different composition were obtained by utilizing either a polyethylene or polypropylene matrix and a wood flour filling. In order to characterize these materials, a series of experiments were conducted to determine density, electric strength, complex dielectric constant components and and dielectric loss factor tgd for various electric field frequencies and at different temperatures. The results show that the dielectric properties are heavily influenced by the filler content with very high registered values in the case of low frequency electric fields and high temperatures. It can be ascertained that samples having a polypropylene matrix have superior electric properties than those having a polyethylene matrix. Finally, the opportunity for utilization within low voltage and industrial frequency electrical engineering applications of the tested composite materials is shown. Keywords: wood-polymer composites, dielectric properties, dielectric spectroscopy

A polyurethane (PU) based on 4,4’diphenylmethane diisocyanate (MDI), copolyester poly(ethyleneadipate) diol (PEA) and extended with butylene glycol (BG) was synthesized via a two steps polymerization technique. The thermal stability of the PU was investigated by thermogravimetric analysis (TG) at temperatures between 30 and 600oC. The synthesized PU was irradiated in an UV exposure unit as such the spectral distribution of the light was a good match for terrestrial solar radiation (200 h, l > 300 nm, Ia = 30 mW cm-2). The modifications in the chemical structures of the PU before and after irradiation were characterized using Fourier transform infrared spectroscopy - attenuated total reflectance (FTIR-ATR) technique. The yellowing index variation (YI) exhibited a systematic trend increase with irradiation time. Our results are in agreement with the formation of quinoide structures, which are colored products resulting from photo-degradation of PU. Keywords: polyurethane, thermal analysis, photostability, thermal stability

In this study, blends of biodegradable matrix as poly(3-hydroxybutyrate) (PHB) and fibers provided by renewable resources were prepared by a melt blending method. Improvement of the compatibility between fibers and polymer was studied using coupling agents: maleic anhydride (MA) respectively, succinic anhydride (SA). Mixtures with two types of fibers were investigated in terms of microscopy, torque, density, tensile strength, melting temperature and contact angle. It is found that the mechanical properties of PHB with cellulose fibers blends were better than PHB and wood fibers. Keywords: polyhydroxybuthyrate, wood fiber, cellulose fiber, coupling agent, blend

When the plastic materials products are obtained by injection into the mould, the fluid plastic mass takes the shape of the cavity and then, in a technological time, the obtained product cools until a temperature which makes possible its unloading without any deformation. Each product or more products may be realized during a period which means the time of one manufacturing cycle. An optimum manufacturing process is a continuous process without waiting times. The paper presents a methodology for the calculation and adjustment of some injection parameters which influence the time of one manufacturing cycle for the plastic materials products realizing. Keywords: plastic materials manufacturing, thermal processes of the polymers injection

This research studies the influence of scratches on the polyethylene gas pipes after squeezing with the squeeze-off tool in order to stop gas flow due to an intervention of the gas pipeline. Problem occurs when there is a need to make a decision whether it is safe to squeeze the pipe with scratches. The goal of the research is to determine the change in the depth of scratches on the polyethylene gas pipe after squeezing with the squeeze-off tool. After the experimental research it was determined that there would be a change in the depth of scratch. The change of the depth of scratch positioned on the squeeze-off ear would be considerably bigger when compared to the depth change of a scratch positioned under the upper cylinder of the squeeze-off tool. Based on the resulting data, it is a recommendation of the author not to squeeze the pipe if it has scratches. If the squeezing if inevitable on the place where there is a scratch, the squeeze-off tool needs to be positioned under the upper cylinder of the squeeze-off tool. Keywords: scratches, polyethylene gas pipes, gas flow,the squeezing

A series of phosphorus-containing polyesterimides has been synthesized by solution polycondensation reaction of an aromatic dianhydride, namely 1,4-[2-(6-oxido-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl)]-naphthalene-bis(trimellitate)dianhydride, with various aromatic diamines. The polymers were easily soluble in polar organic solvents, such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, tetrahydrofuran and chloroform. They showed high thermal stability, the decomposition temperature being above 400oC and the glass transition in the temperature range of 174-194oC. Due to the presence of phosphorus the polymers gave high char yield in thermogravimetric analysis. Solutions of the polymers in N,N-dimethylacetamide showed photoluminescence in the blue region. Keywords: polyesterimides, phosphorus-containing polymers, good solubility, thermal properties, photoluminescence

The new organic coatings were realised from polyurethane resin and alkyd+melamine-formaldehyde resins. The electrochemical techniques of the electrochemical impedance spectroscopy (EIS), cyclic potentiodynamic polarisation and linear polarisation were applied and the tests were carried out in a normal aerated 3% NaCl solution at ambient temperature. Also, open circuit potentials in 3% NaCl solution were monitored for 300 immersion hours. Salt spray tests were carried out according to ASTM B117 Standard. An electric equivalent circuit with two time constants representing the barrier characteristics of the intact organic coating, and the corrosion process occurring at the substrate/paint interface was fitted. The both coatings revealed very good protective properties, assuring a very good resistance for about 8 years in the ambient environment. Keywords: protective films, immersion tests, salt spray tests, EIS, cyclic polarisation