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Theoretical and experimental bases for estimating the thickness of the thin anisotropic layers in order to obtain and analyze the total polarized light are discussed, having in view the numerous applications in fundamental and applicative researches. The formulas expressing the thickness of the type wave, half-wave, quarter-wave layers as functions of the birefringence of the anisotropic medium are established. The obtained results could be used for obtaining anisotropic layers, introducing a desired phase difference between ordinary and extraordinary radiations, made up of inorganic crystals or from liquid crystals with a high degree of order at the room temperature. Keywords: wave-; half-wave and quarter-wave plates; birefringence; inorganic crystals; liquid crystals

Two copolymers based on N-(4-formyl-fenoxy-4`-carboylphenil)maleimide have been synthesized. The first one was prepared by free radical polymerization of this monomer with styrene. The second one was obtained by chemical modification reaction with p-amino-azobenzene of the resulting first copolymer. The structures of these polymers were identified and characterized by IR, 1H-NMR and UV-VIS spectroscopy. A strong birefringence in the melting state was observed for some of these compounds, suggesting a possible liquid crystalline behaviour. Keywords: maleimide, alternant copolymers, azobenzene groups

Transparent thin films of poly(4,4’-azodiphenyl) and poly(4,4’-azostilbene) were obtained by vacuum thermolysis or photochemical decomposition of the corresponding aromatic diazides. Taking into account the working conditions, the thickness of transparent films was about of 0.1 – 0.5 mm. Surface morphology was investigated by atomic force microscopy (AFM). The influence of different factors on the surface morphology in azoaromatic polymer films such as evaporation rate, diazide quantity, support temperature, distance between support and oven has been shown. Atomic force images have revealed several types of morphology: high roughness films with prominent hills and valleys, films with satisfactory roughness but having single hills, and films with smooth surface (average roughness about 1 nm). Keywords: azoaromatic polymers, atomic force microscopy, surface morphology

Thin films, in the range of tens of micrometers thickness, have been prepared by casting onto glass plates the chloroform or N-methylpyrrolidone solutions of poly(1,3,4-oxadiazole-ether)s. The polymers have been prepared by nucleophyilic substitution polymerization technique of 2,5-bis(p-fluorophenyl)-1,3,4-oxadiazole with various aromatic bisphenols, such as 4,4’-isopropylidenediphenol, 4,4’-(1,4-phenylene-diisopropylidene)bisphenol or 4,4’-(hexafluoroiso-propylidene)diphenol. They showed high thermal stability with decomposition temperature above 410°C and glass transition temperature in the range of 187-211°C. The polymer films exhibited good mechanical properties with tensile strengths in the range of 36.92- 44.50 MPa, tensile modulus in the range of 1.42-1.74 GPa and elongation at break in the range of 3-91%. Electrical insulating properties of polymer films were evaluated on the basis of dielectric constant. The values of the dielectric constant at 10 kHz were in the range of 2.98-3.18. Keywords: poly(1,3,4-oxadiazole-ether)s, thin films, mechanical properties, dielectric constant

The paper analyzed the chemical resistance of polyethylene (PE) pipes, some attention paid to the general phenomenon of degradation which influences polyethylene life. The influence of synthetic condensate (50% (by mass) n-decane and 50% (by mass) 1-3-5 trimethylbenzene) about the strength and durability of polyethylene pipes was established . Keywords: polyethilene pipe, chemical resistance, strength, durability.

In this paper, the behaviour of polyurethane protective sheets on metallic surfaces in g-radiation field was studied. The irradiation effects consist of the decrease in the sheet thickness and the worsening in the brightness of modified polyurethane protection. Kaywords: polyurethane protection, irradiation

The paper presents some basic considerations to establish the optimum conditions for designing the ultrasonic equipment employed in plastic flow activation. In the first part, the paper presented general considerations and recommendations for the design of the ultrasonic horns. The associated conditions are submitted at a critical discussion correspondingly at the particular industrial applications. There was emphasized a particular effect of the ultrasonic activation – namely “the thermo-pellicular effect”- specific for the particularized activation conditions of the viscous-elastically mediums under pressure. The effect is characterized by the appearance of a fine layer of melted overheated material with lubricant effect on the lateral side of the ultrasonic horn. The paper includes a computer-aided application focused on the design of an ultrasonic horn employed in plastic manufacturing and some particular applications in plastics injection and extrusion. Keywords: plastic, flow, rheology, ultrasonic, activation, design, concentrator, industrial, application

Polystyrenes with pendent diquaternary 4,4-bipyridinium groups are polystyrenes containing pendent viologen groups. They were obtained by the reaction of chloromethylated polystyrene with N-monoquaternary-4,4’- bipyridinium bromides as: N-(p- H, NO2, Cl) phenacyl-4,4’-bipyridinium bromides and N-carbomethoxymethyl/ethyl-4,4’-bipyridinium bromides (2a-e). Thermal stabilities of polystyrene with pendent viologen groups were investigated. The influence of the chemical structure of pendent viologen groups on the thermal stability was performed by thermogravimetric analysis in the dynamic conditions of temperature and atmospheric air. The substituted compounds undergo a thermal degradation process that took place by a complex mechanism in three steps. These steps are disscused from both kinetic parameters and thermogravimetric characteristics points of view. The thermostability of low molar mass compounds 1a-e decreases in the following order: 1c > 1a > 1e > 1d > 1b and the same thermostability order was found in the case of chloromethylated polysulfone derivatives (2c > 2a > 2e > 2d > 2b). Keywords: Thermal behaviour, thermal stability, chemical modificated polystyrene, N-phenacyl and N- carbomethoxymethyl/ethyl- 4,4’-bipyridinium groups, viologen group

This paper presents the influence of styrene-butadiene block-copolymers on the modification of high density polyethylene wastes. The modification of this polyolefine is a means of improving the mechanical properties, especially the impact strength, in order to increase the posibilities of recycling high density polyethylene wastes. Keywords: styrene-butadiene block-copolymers

The residence time distribution at the exit of mixing zone in a fully intermeshing, corotating twin screw extruder was determined with a stimulus-response technique. The operating parameters investigated were screw speed and feed rate. The residence time decreases with increasing screw speed and feed rate. Keywords: residence time distribution, corotating twin screw extruder