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In this study were synthesized some polyurethanes based on polycaprolactone diol (PCL) with Mw=2000g/mol and 4,4’-diphenylmethane diisocyanate (MDI), using as chain-extending agents different linear diols with methylene number between 2 and 6, without adding catalysts. Effect of the diisocyanates concentration and chain extender structures on the polyurethanes has been discussed with reference to the thermal stability and mechanical properties. The physical and mechanical properties (hardness, stress-strain, resilience, abrasion resistance, etc.) of these polymers were measured according to standard methods. All the polymers were characterized by conventional methods. Thermal analysis (TGA and DSC) were used for characterization. The structures were confirmed by infra-red analysis (IR). The results showed that the thermal stability and mechanical properties of the final products can be controlled by the amount of the MDI and/or of the chain extenders nature. Keywords: polyurethanes, mechanical properties, thermal stability

The paper presents the synthesis of bis-Mannich polyolic compounds with high aromatic content and thermostable structures. Synthesis of bis-Mannich polyolic bases was performed by the reaction of acidic substrates such as phenols with the Mannich precursor reagent, such as bis-1,3-oxazolidine derivate compound, followed by alkoxylation in the absence of a catalyst. Applications of these polyols are poured and “spray” rigid polyurethane foams synthesis with high thermostability and enhanced flame retardancy properties. Keyword: N,N’-hydroxyethyl-bis-1,3-oxazolidine; bis-Mannich polyether polyols; rigid polyurethane foams

The study consists of a new know - how applied to the organic optical glass used to manufacture optical components. The study was developed on several organic optical glasses, usually used to manufacture pieces with optical properties. The innovative methods, subject of this paper, are manufacturing active optical surfaces with a high quality surfaces. That is the reason of complex control, based on different methods which can reveal changes of inner or outer structure thinking of nanometric level. Keywords: organic optical glass, nanometric structure

Polymers with polyimide, polyamide or poly(amid-imide) structure have been obtained by polycondensation of 2,2-bis(3-amino-4-oxyhexyloxy-phenyl-4’-butoxyazobenzen) hexafluoropropane with hexafluoroisopropylidene diphthalic dianhydride or two different aromatic diacid dichlorides. These polymers have been characterized by FTIR and UV-VIS spectra, molecular mass determination, solubility and optical properties. The photochromic behaviour upon UV-Vis nopolarized and polarized light was also investigated. Keywords: pendent azobenzene groups, polyimide, polyamide, polyamid-imide, photoinduced optical properties

Copolymers based on dicyclopentadiene and maleic anhydride have been reacted with several aromatic amines (typical polymer-analogous reaction) to obtain the corresponding amides, and subsequently imides. An appropriate procedure has been established and the conversion has been appreciated. All the products have been characterized from the structural point of view, as well as by measuring the improved thermal properties. Keywords: dicyclopentadiene; maleic anhydride; polymer-analogous reaction; thermal properties

New reinforcing agents based on modified montmorillonite with different amines and polyhedral oligomeric silsesquioxanes were synthesized and characterized by different techniques like FTIR Spectrometry, Thermogravimetric Analysis (TGA), X-Ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC). DSC analyses show that the presence of the modified montmorillonite leads to an increase of epoxy resin reactivity due to the catalytic effect of the montmorillonite modifier which included amino groups. The glass transition temperature (Tg) for the final hybrid systems which contain modified montmorillonite with amines exhibits lower value than the epoxy systems without any reinforcing agent. The thermostability of the final hybrid systems was not influenced by the introduction of these reinforcing agents. Keywords: epoxy, layered silicate, polyhedral oligomeric silsesquioxanes, glass transition temperature, nanocomposites

New polymeric nanocomposites based on nanostructured reinforcing agents as Polyhedral Oligomeric Silsesquioxanes (POSS) with methacrylic groups were synthesized and the influence of POSS type was studied. As polymer matrix a mixture of functionalized POSS and triethylene glycol dimethacrylate (TEGDMA) was used by replacing the classical diglycidyl methacrylate monomer (BisGMA) with various POSS functionalized with methacrylic groups. The obtained nanocomposites were characterized by spectroscopic methods (FT-IR, RAMAN), thermal analysis (TGA, DMA) and scanning electron microscopy (SEM). Keywords: polyhedral oligomeric silsesquioxanes, nanocomposite, thermostability, FT-IR, RAMAN, TGA, DMA, SEM

The aim of this study is to investigate the interaction between pure collagen and mineral phases like hydroxyapatite. For that purpose, collagen fibers were mineralized starting from hydroxyapatite aqueous precursors. The mineral phase identification was made by XRD, the collagen-hydroxyapatite interaction was studied by IR spectroscopy, the microstructure of the composite materials was investigated by SEM and the amount of mineral phases’ deposition was evaluated by ATD-TG. Ultrasonication was used in order to evaluate the strength of the collagen-hydroxyapatite bond. The obtained results showed that it was obtained a collagen – hydroxyapatite composite material, characterized by a strong interaction between the collagen fibers and the hydroxyapatite crystals, which can be successfully used as a bone substitute. Keywords: collagen fibres mineralization, hydroxyapatite, electrostatic interactions

The dynamics of the plasma discharge through spontaneous symmetry breaking as double layer Langmuir, anodic patterns etc., is treated by means of the fractal description. Considering that the charge carrier movements take place on fractal curves, the electric charge transport is studied in an extended model of scale relativity. Using the motion equation for the complex speed field for the irrotational movement the generalized Schrödinger equation is obtained, and in the absence of dissipation a generalized Korteweg de Vries type equation is obtained. The process is also analyzed at the microscopic scale, when the electrical conductance increase is controlled by means of the soliton coherence. When the external field exceeds a critical value, the solitons which stocks the energy break down and simultaneously release the energy to the environment. The same mechanism can explain the charge transport in composite materials (e. d. nanostructures). Moreover, some correspondences between the theoretical model and the behaviour of the patterns generated by laser ablation are analyzed. Keywords: fractal space-time, charge transport mechanism, nanostructures, composite materials

This work presents a theoretical model of calculation of cylindrical assemblies joined with adhesive, based on an energy method. After the determination of the cinematically acceptable field of stresses, according to the applied load, a variational calculus on the expression of elastic potential energy leads to the complete expression of the stress field in the whole assembly. A first parametric analysis (geometrical and physical parameters) is carried out on an assembly of tubes and makes it possible to deduce the optimal length and the thickness of the adhesive. The model is validated by comparison with a finite elements model. For the assembly, the total force-displacement behavior is well defined. Thus the analytical model makes it possible to determine the rigidity of the assembly and to obtain a simple formulation very rapidly which gives the total behavior of the assembly. Keywords: adhesive joints; glass fibers; modeling; finite element analysis, stress transfer