Volume 40, Issue 1

Abstract: There were investigated the performances of some UV stabilizers systems in the surface layer (gel coat) of unsaturated polyesthers. The changes in colour and in gloss were determined using accelerated degradation methods as well as natural ageing. The correlation of results allowed the proposal of a degradation model of the polyestheric surface layer under UV radiations action.

Abstract: This paper presents the synthesis and study of some Mn(II) coordination polymers hybrid with the following acids as ligands: dibuthilphosphinic, dibuthiltiophosphinic, dibutildithiophosphinic, dioctilphosphinic, dioctiltiophosphinic, dioctilditiophosphinic. The study was performed by means of chemical analysis, gel chromatography, IR spectroscopy, ESR, X-ray diffraction, thermogravimetry. The experimental results were used to propose the structural formulae of these compounds and to calculate the kinetic parameters of the thermal decomposition reactions.

Abstract: The radiation stability of low density polyethylene in the presence of several additives as antioxidants (two derivatives from rosin, two commercial stabilizers, Irganox 1076 and Irganox 1081 and elementary selenium) was carried out by oxygen uptake method. The values of oxidation induction times of stabilised PEjd were discussed. A stabilisation mechanism concerning derivatives of rosin was reported. The antioxidant efficiency of studied compounds was compared to propose a reliable alternative to commercial antioxidants for the radiation sterilisation of PEjd. Keywords: LDPE, oxygen uptake, gamma irradiation.

Abstract: Manufactured in various geometric forms, containing secondary materials (colorants, reinforcements, fireproof etc.), all these make the composites based on resin-textile fibre, basic materials for obtaining lateral walls, ceilings, floors, compartments for luggage and sanitary installations. The materials were made as stratified plates using polyesteric resin POLIKON P210 FA and natural fibres: cotton, flax and hemp. This paper presents the determination of mass and volume content of the resin in these composites.

Abstract: A laurylsulfate-selective electrode is presented. The sensing material of the electrode consists of an ion pair 1:1 water insoluble salt that has been prepared using sodium laurylsulfate and hexadecyl trimethylammonium bromide and was immobilized in a PVC membrane plasticized with orto-nitrophenyl octyl ether. This electrode gives a linear response for sodium laurylsulfate between 8x10-7 - 5x10-3 M with a slope of 57,7 mV per decade of sodium laurylsulfate concentration. The electrode has been applied to potentiometric titration of anionic surfactant using cationic surfactant as titration agents.

Abstract: In this paper it is presented a creep model in the theory of viscoelasticity for polymeric materials.

Abstract: This paper deals with synthesis and characterization of some copolyamides 6/12 obtained by rotational molding via activated anionic ring–opening copolymerization of e–caprolactam with laurolactam. Sodium bis[(2–metoxyetoxy)e–caprolactam] aluminate, as initiator and N,N’–[methylene–di(1,4–phenylene)bis–carbamoyl]–bis–e–caprolactam, as activator were used. The initial mold temperature (initial polymerization temperature) was kept constant at 160oC. The incorporation of laurolactam into nylon 6 chain depresses both in the degree of crystallinity and the melting temperature of nylon 6/12 copolymers. The notched Izod impact strength of the copolymers increased as the laurolactam content was increased, while the flexural modulus and the water absorption decreased.

Abstract: The main purposes of this article are: 1) the minimization of an objective multi-criterial function which implies the reaction time, the polidispersion coefficient and the monomer conversion; 2) the obtaining of reaction conditions (temperature and initiator concentration) which determine the realisation of some final imposed values for conversion and polymerization degree. Within the optimization algorythm there were successively considered as decision variables: 1) a single value of temperature (the isothermal case) and the initiator concentration; 2) two temperature levels and the initiator concentration; 3) thee temperature levels. Of the three optimization strategies, the right one was proved to be the temperature trajectory constituted of two values. The obtained optimal politics essentially depend on the objectively chosen function and on the weight factors attached to each interest measure.

Abstract: The ortocresol, the p-aminophenol and the formaldehyde were taken in different molar ratios and condensed in the presence of hydrocloric acid as catalyst and of toluene) N-methyl pyrolidone mixture as extraction agent of the reaction water. The condensing products are polymers with a low molecular mass, friable solid substances soluble in polar organic solvents which show colors from transparent pink for the ortocresolformaldehidic resin, to dark brown for the p-amino-phenolformaldehidic one. The obtained formaldehidic resins were structurally characterized using IR and 1H-RMN spectroscopy. The thermal properties were also investigated.

Abstract: This paper presents the performance of two aminic antioxidants (TMQ and PBN) and a phenolic antioxidant (SPH) in formulations based on diene rubbers, typical for tyre treads. An imidazoline was used as secondary accelerator and the influence of antioxidant nature was investigated following its influence on scorch safety, curing behaviour, tensile strength, fatigue behaviour, abrasion performance, and thermo-oxidative degradation.

Abstract: The replacement of classical materials used in industry with other more important, cheaper and environment friendly ones and also the prevention of corrosion is one of the goals in the research area. Electrotechnical industry and engineering needs this special material. The conductive and semiconductive coatings belong to these special materials and occupy a large application domain in modern industry, used to remove the electrostatic charges, and for the shielding effects (i.e. Faraday screen, protective coat for the high voltage cables etc.).In this paper it is studied the stability in time of semiconductive lacquers based on polianiline.

Abstract: Flavonoids pigments exert a broad range of biological activities in both plants and animals. Natural polyphenols mainly occur as glycosilated molecules, usualy with a b-linked sugar. In this paper are cited several methods and techiques uses in flavonoid analysis. Chromatographic methods are usually cited techniques for quantifying flavonoids. HPLC methods utilizing UV detection system are commonly employed, as the conjugated p-systems of flavonoids afford good UV absorbtion. IR spectroscopy is useful to determine the functional groups attached to the basic structure of the flavonoid molecule and this is of value in the later interpretation of NMR scans. In order to determine that the isolated compounds are flavonoid pigments, the UV spectra (with and without adding the specific agents) are compared with literature data.