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For calendaring sheets with a desired final thickness, the design process of the calender unit includes, among other parameters, the calculation of the flow velocity and pressure fields in the gap between the rolls. In this paper, the fundamental aspects about the behavior of the molten polymer during the calendaring process are analyzed and the relations between the variables of interest are determined for calendring of high density polyethylene (HDPE), polyvinyl chloride (PVC) and ethylene styrene interpolymers (ESI). Keyword: plastic materials, calender, calendered sheet

Lubricants based on vegetable oils are a growing in attraction various applications. Environmentally friendly, vegetable oils and their derivatives constitute alternatives for a large variety of mineral based lubricants. New lubricating oils obtained from mixtures of vegetable oils (sunflower, SFO and rapeseed oil, RO) and synthetic diesters (di-2-ethylhexyl-adipate (DOA)) are studied. The physico-chemical characteristics of all these mixtures are given together with the differential scanning calorimetry (DSC) and thermal gravimetric (TG) analyses. Keywords: vegetable oils, diesters, environmentally lubricants, di-2-ethylhexyl-adipate, sunflower oil, rapeseed oil

The biodegradable polymeric materials can be achieved based on several methods among which, the compounding of natural polymers with synthetic ones has a significant utility. The biodegradable materials based on polyvinyalcohol (PVOH) and starch have a practical interest because can be entirely destroyed in environment, in controllable times based on the PVOH hydrolysis degree. The silicate presence in the PVOH - starch systems determines the increasing of the glass transition with 4 - 11 0C and of the maximum of the melt temperature with 10 0C. If the silicate was functionalizated then its interaction with the polymer is underlined by the melting uniformity . Keywords: polyvinylalcohol, starch, thermic properties, nanocomposites

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