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Mechanical behaviour of removable partial dentures is a priority among experimental papers, in order to define the fracture mechanism of acrylic resins. Present paper presents experimental results concerning mechanical behaviour of two different dental acrylic resins, respectively Meliodent and Royaldent. There are determined mechanical characteristics on Zwick Roell Equipment with testXpert system. The fracture samples were examined on stereomicroscope Olympus. The difference in mechanical behaviour is explained in terms of stereomicorscopic analysis. Keywords: dental resins, removable partial denture, stereomicroscopy, fiber, composite material

The paper presents a theoretical-experimental approach of a particular class of composite materials known as multiphase composites in order to retrieve its effective elastic coefficients and identify the major influencing factors on these variations. Moreover, in the paper is being presented a particular homogenization concept based on the well known theoretical predictions from the micromechanics of composite materials approaches, the Mori-Tanaka that applies to the particle reinforced composites and Halpin-Tsai that applies to the random fibre composites. The theoretical values were used against the experimental data, the later being retrieved during a simple tensile, compression and three point bending tests at room temperature on samples made using a self-developed manufacturing technology. The samples were ceramics and metal reinforced particles of various volume fraction embedded along with random E-glass fibres into a polyester matrix. Keywords: composite, multi-phase, elastic coefficient, micromechanics, testing

Thermal stability of alendronate sodium in a mixture with cross-linked acrylic acid polimers and chitosan, formulated and preparated as oral matrix systems, was qualitatively evaluated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and infrared spectroscopy (FT-IR). The results of the study have shown alendronate stability in association with carbopol and chitosan. DTG curves and FT-IR results suggest certain interactions between carbopol and chitosan, most probably ionic and hydrogen bonds. We consider that the nature and intensity of these bonds could be a positive factor decreasing pH dependence of Carbopol in releasing drug substance. Keywords: alendronate, carbopol, chitosan, thermal analysis

The work presents the main results obtained at the application of the ultrasonic energy in the separating process of the rubber on the metallic insertions in the case of the transporting belts. Results refer mainly at the influence ultrasounds’ application has over the specific resistance at extraction of the metallic insertion from the rubber matrix, and these are quantified through an efficiency coefficient at extraction. The importance of the results presented in the work derives from the fact that the separating processes of the rubber on the metallic insertions are complex enough and big energy consumers, and the results presented in the work can be applied in practice and they allow a substantial increase of the economic profitability for the capitalization processes of the wastes of transporting belt reinforced with metallic insertion Keywords: belts, ultrasonic energy, rubber, metallic insertions

Production process of plastic products depends significantly on cost of quality, time to market and cost to produce appropriate molds. Basic course of improvement and rationalization of production process for plastic injection molds is directed on automation design mold and their process planning. Working area of process planning in large number of cases is the bottleneck in production systems, because of impossibility of development multipurpose program system which would be effective in planning and designing a huge number of activities that makes process planning. The model and program system for automated process planning for plastic injection molds manufacturing have been developed, in order to solve this problem. This solution presents integrated CAPP system, which is based on integration of CAD, CAPP and CAM activities. Keywords: Plastic injection mold manufacturing, CAPP, Data base, Knowledge base

The solution properties of some cationic polyelectrolytes with ammonium quaternary centers either attached to an acrylic macromolecular chain (polycation PDMAEMQ type) or in the backbone (polycation PCA type) have been measured in order to identify how charge density, polyelectrolyte concentration, solvent polarity as well as temperature influence their behavior in solution by viscometric, conductometric and rheological methods. The viscometric data revealed that all copolymers PDMAEMQ exhibit a polyelectrolyte behaviour in water and methanol and were plotted in the terms of Rao equation. Straight lines were obtained in all cases, allowing the calculation of intrinsic viscosity, [h]. Data from the conductometric study emphasized for PDMAEMQ50 and PCA5 an increase of the equivalent conductivity values, L, with decreasing concentration over the whole concentration range in water, methanol and their mixture (1:1). The comparison between the complex viscosity values h*, at the same polymer concentration, cp = 4%, for PCA5D1 and PCA5 shows higher values in the whole interval of temperatures under study (T = 10-60 C°) and a pseudoplastic behaviour at temperatures higher than 50°C for the former system. Keywords: polyelectrolyte, viscosity, electrolytic conductivity, rheology

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