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Water soluble cadmium selenide (CdSe) nanoparticles were chemically obtained by polymer assisted synthesis at 70 Celsius degree from aqueous solution, using Cd(CH3COO)2·2H2O or Cd(NO3)2·4H2O as cadmium source and H2SeO3 as selenium source. The clustering of CdSe nanoparticles synthesized in poly(amidehydroxyurethane) matrix was clearly revealed by X-ray diffraction and Atomic Force Microscopy films studies. The obtained CdSe nanocrystallites have hexagonal symmetry with an average dimension of 25 nm. The Fourier Transform Infrared spectra show the interaction between the nanoparticles and urethane carbonyl and C – O – C etheric groups of polymer. The dimension of CdSe – polymer entities in water solution was explored by Laser Diffraction method and confirmed the capping of CdSe nanoparticles by the polymer. Keywords: CdSe, nanoparticles, polymer assisted synthesis, structural characterization

The flow rate coefficient was calculated both theoretically, based on calculus relationships, and experimentally, based on data obtained on two extruders with screw diameters of 45 mm and 90 mm, respectively. The concordance of the theoretical results with those obtained experimentally in two situations were verified, namely: free discharge, no backpressure, and discharge with backpressure. Keywords: flow rate coefficient; feeding zone; single screw extruder; flow rate

Due to their lightweight, exceptionally high strength and modulus, high stiffness, good fatigue life, and excellent corrosion resistance, polymer matrix composites are increasingly being used in the aircraft and spacecraft industry. Nowadays, a significant amount of advanced polymer composites is used for military and commercial aircraft and satellite components. Due of their low density, higher physical and mechanical properties and low manufacturing cost, these materials have replaced metals, such as aluminum alloys, in many applications. This paper deals with the class of polymer composites, new material recipes and testing results. This approach refers to the possible use of ferrite additive to improve mechanical and magnetic properties of polymer composites. Keywords: lightweight, polymer, composite, ferrite

Construction of passive insulation elements in neoprene single microstructure mixture has demonstrated that the isolators can have the necessary elastic characteristics but low internal damping. The reduced scale models have in the structure viscoelastic materials basing on natural rubber symmetrically distributed in respect to the geometrical reference system chosen for the isolator. The materials consisting of natural or synthetic rubber are used as filling elements symmetrically located so that, globally, the isolator can be properly characterized both at compression and shear. For the present paper there were used two material types modelled as Voigt-Kelvin and Hooke-Maxwell elements. Key words: rheological modelling, antivibrating isolator, composite neoprene

Pralidoxime chloride (PAM) was encapsulated in biopolymeric membranes in order to evaluate the kinetics of release in aqueous solution. PAM is an efficient cholinesterase reactivator with a pronounced hydrophilic character. The biopolymeric membranes were prepared by crosslinking, directly in aqueous solution and the monodisperse spherical microcapsules made by this method had diameters between 1 and 3 mm. PAM was embedded “in situ” in microcapsules prepared from natural polymers as sodium alginate, chitosan and gelatin. The release data were fitted by first order kinetic equation, Weibull, Peppas and Higuchi semiempirical equations to obtain the kinetic parameters of controlled PAM release. The embedding of PAM in biopolymeric membranes was achieved in order to prepare a sustained release pharmaceutical formulation for oral administration. Keywords: biopolymeric microcapsules, Pralidoxime chloride, drug release

The most modern restorative interventions in dental practice are mainly based on a new generation of composite materials specialy designed for this kind of applications. Their complex structures offer a quasi-plastic behavior concerning the special tribological phenomenon developed in the intraoral environment. Starting from this, the paper intends to present the experimental data obtained as research results for two composite materials - InLine (IVOCLAR) and HeraCeram (HERAEUS Kulzer). The study is focused on the influence of the most important mechanical factors from occlusion areas such as loads, lubricants, speeds, composite materials hardness concerning the wear processses and their influence onto the mastication areas. Keywords: composite materials, tribology, wear, dental medicine

The aim of this study is to obtain and characterize a range of hybrid polymeric films with different collagen content and synthetic poly-alcohol as polyethylene glycol (PEG). Films were obtained using a “casting solution method” by a cross-linking process at room temperature. The new collagen hybrid biofilms are devoted to cell growth and proliferation. Keywords: collagen gel, hydroxyapatite, ternary hybrid biofilms

Lyocell fibers are ecological cellulose regenerated fibers and represent the most important discovery in the field of “artificial fiber engineering”. These fibers can be situated at the border between natural fibers (in terms of comfort, biodegradability) and chemical fibers (by high resistance in dry and wet environment, low contraction). In order to characterize the structural Lyocell fiber properties, electronic microscopy analyses, birefringence and X-ray diffraction have been accomplished. The present analysis on the structural properties of Lyocell fibers allowed to conclude that the microscopic images depict that Lyocell fibers present uniform longitudinal aspect and regular cross-section; the Lyocell fiber birefringence is 1.6 times higher than similar feature of viscose fiber (0.04263 as compared to 0.0265) and the diffraction analysis reveals that the distortion degree of the crystal lattice of Lyocell and viscose fibers is in accordance with the crystalline factor. The average tenacity – deformation diagrams for Lyocell and viscose fibres, in conditioned and in wet medium, allowed to determine the rheological parameters of the fibers. Keywords: Lyocell fiber properties, electronic microscopy, birefringence, diffraction analyses

Lactic ester of maleoabietic acid (RAMALA) was obtained by chemical reaction between Diels-Alder adduct of resin acids with maleic anhydride (RAMA) and lactic acid (LA). The obtained product was characterized by elemental analysis and by spectroscopic methods (IR and NMR). Curing reaction of three epoxy resins (diglycidylether of bisphenol A (DGEBA), diglycidyl ether of hydroquinone (DGEHQ) and diglycidylaniline (DGAN), with (RAMALA) in the presence of triethylbenzylammonium chloride (TEBAC) as catalyst was examined by differential scanning calorimetry (DSC) at different heating rates. Using the literature methods the kinetic parameters of crosslinking reactions were obtained. The activation energies of the curing reactions varied in the range of 48 to 85 kJmol-1 depending on epoxy systems. The thermal behaviour of cured products was also investigated using dynamic thermogravimetric analysis (TGA) technique. The cured products present good thermal stability and the activation energies of the degradation process exhibit values between 82 to 155 kJ×mol-1. Keywords: Diels-Alder adduct of resin acids, lactic ester of Diels-Alder adduct of resin acids with maleic anhydride ,epoxy resin, crosslinking reactions, thermal properties

The qualitative and quantitative information concerning the dependence between the kinematic viscosity and the activation energy of the viscous flow by the polyvinyl chloride – thermoplastic polyurethane blends composition were obtained. The results reveal that the blend composition and the melt temperature are the most important parameters that control the PVC – TPU blends melt processing. A high injection speed increases both the tensile strength and the breaking elongation. The shorter time for the mould loading increases the tensile strength and decreases the breaking elongation. The measurement of the rheological properties based on the MFI methods is a good instrument for the estimation of the rheological properties of the polymeric blends in practical conditions Keywords: polyvinyl chloride -thermoplastic polyurethane blends, rheological properties, kinematic viscosity, melt viscous flow, activation energy of the viscous flow