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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

A solvent and catalyst-free synthesis of a polyphosphate was accomplished. The reaction involved a gas-liquid polycondensation between phenylphosphoric dichloride and phenolphthalein. The polyphosphate was characterized by IR, 1H-NMR, inherent viscosity, thermal analysis and molar mass. Polyphosphate was stable up to 260oC. Keywords: gas-liquid polycondensation, polyphosphate

The structural characteristics of polymeric composites based on EPDM, (ethylene-propylene-dien monomer) rubber, which have various percentages of high density polyethylene, were studied by IR spectroscopy and optical microscopy, evidencing the influence of processing parameters. The EPDM rubber was vulcanized using either sulphur and accelerators or peroxides. The influence of the dynamic conditions (rotation rate during the mixing of rubber with polyethylene) on the solvent retaining by maintaing 1-24 hours in benzene, chloroform and MEC (methylethylcetone) was shown by weighing the samples. The results of research could be used for choosing the suitable compositions, processing conditions as well as the fields for application of these composites. Keywords: EPDM (ethylene-propylene-dien monomer) rubber, polyethylene,IR spectroscopy, microscopy

In the paper, a stress strain analysis in the area of central ligament of a cruciform glass-epoxy specimen is presented. Investigation was done experimentally, using strain gauges technique, by application of six gauges in the stress concentration area. The validation of a theoretical model (a special type of a finite element), which was created by authors for analysis of the laminate composite structures, was the aim of this study. A good agreement between numerical calculus and experimental results was observed. Keywords: experimental validation, finite element method, epoxy resin, lamina, cruciform specimen, strain gauges technique