Browse Articles

The paper focuses on the development of composite materials based on bacterial cellulose and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV). Natural composites were obtained from bacterial cellulose membranes and chloroform copolyester solutions (various mass ratios). The composite membranes were characterized by FT-IR spectroscopy, X-ray diffraction, SEM morphology, contact angle measurements and thermogravimetric analysis. Cellulose nanofibrils coating and/or precipitation with PHBHV particles was observed. The biocompatibility of composite materials was assessed by using L929 mouse fibroblast cells monolayers. Possible applications of these composite materials are focused on blood vessel engineering and/or wound dressing management. Keywords: bacterial cellulose, polyhydroxyalkanoates, composites, tissue engineering

Bimetallic Pd-Ag nanoparticles (NPs) were obtained by polyol method in the presence of poly (vinylpyrrolidone), PVP, as capping agent. The reduction of silver and palladium precursors was performed in argon inert atmosphere by successive reduction, or coreduction approach. In the successive reduction, AgNO3 solution was injected in the ethylene glycol solution of PVP at 140°C, followed by the injection of [Pd(NH3)4]Cl2 solution. The obtained bimetallic Pd-Ag NPs exhibited cluster structure, with the surface reach in silver. The NPs size was in the range of 30 – 58.5 nm with the average dimention of 41.5 nm. The coreduction approach consists in the hot injection of both metal precursors as complex ammine dissolved in ethylene glycol. By this method, smaller Pd-Ag NPs with the average sizes in the range 16 – 30 nm were obtained, depending on the synthesis parameters. The influence of metal cations : PVP molar ratio, metal cations concentration, Ag : Pd atomic ratio and the reduction temperature on the composition and morphology of the bimetallic NPs was studied. For both reduction approaches, based on the experimental data, two different reduction patways were proposed. Keywords: bimetallic nanoparticles, Ag, Pd, PVP, polyol method, coreduction, successive reduction

This study was focused on the synthesis of some new hybrid materials based on poly(amidoamine) dendrimer and halloysite designed for 5-Fluorouracil encapsulation. Different techniques like Spectroscopic methods (FTIR, XPS and UV-Vis) and thermogravimetric analysis were used to characterize the hybrid materials. The morphology of the hybrid materials was pointed out using Scanning Electron Microscopy ( SEM) analysis. The obtained results showed that the drug encapsulation efficiency of the hybrid materials was strongly influenced by the interactions between dendrimer-halloysite and drug molecules. Keywords: dendrimer, halloysite, 5-fluorouracil, UV-Vis, X-Ray Photoelectron Spectroscopy

Direct photoreduction and photosensitization are powerful approaches for the in-situ synthesis in a polymer matrix. A silver–acrylate nanocomposite was prepared using a novel one-pot strategy involving simultaneous photoinduced reduction and free radical polymerization processes. The fabrication of metal nanocomposite was performed using an acrylate functionalized oligomer (polyethylene glycol 600 diacrylate) and a silver salt (AgNO3). The formation of Ag-nanoparticles was followed by UV–Vis spectroscopy which shows a surface plasmon band at a wavelength range between 410 and 440 nm. Transmission electron microscopy revealed that the synthesized nanoparticles were spherical in shape with a diameter between 5 to 20 nm. The polymerization process was followed quantitatively by infrared spectroscopy, monitoring the disappearance of the characteristic bands for the acrylate double bonds (1410 cm-1). The optimum conditions for obtaining the silver-polymer nanocomposites have been determined (silver precursor concentration, molar ratio silver precursor/photoinitiator, irradiation time and intensity). A reaction mechanism was proposed to explain the polymerization rate dependence on the silver cations content. Keywords: Silver nanoparticles, photo polymerization, acrylate, nanocomposites

In this paper, data on Melana-type polyacrylonitrile fibres dyeing with Crystal violet (CV) - triphenylmethane dye- in the presence of maleic acid copolymers with vinyl acetate (NaM-VA) or styrene (NaM-S) are presented. Mathematical models of the studied dyeing processes have been developed and the necessary information on their significant factors is produced by means of experiment planning methods, known as Design of Experiment (DoE) or Experimental design. Optimal correlations between the application conditions and the colour differences obtained on Melana-type fibre have also been studied. Keywords: Melana fiber, Maleic copolymers, Crystal violet dye, Color differences, Statistic modeling, Optimization process

Difficulty to objectively determine the moment of bone fracture consolidation by classical imaging methods makes necessary the development of a method that will allow establishing, by objective criteria, the moment in which biomechanical loading of the injured bone segment may be permitted. We propose a method based on the approximation between bone diaphysis and a beam, analysing its behaviour under frequency excitation at one end and measuring the vibrations at the other end. Variation of parameters measured in the structurally sound structures compared to the fractured ones, as well as the possibility to analyse their evolution in the presence of osteosynthesis materials used for the surgical treatment of fractures is ascertained. The existence of composite plastic materials of which the used anatomical bone mould for this experiment is made simulates the real pathological situation, which allows extending the determinations to clinical cases. Key words: bone, fracture, mould, polyurethane, osteosynthesis material, composite material

The paper presents a comparative analysis between the performances of pressure sensitive adhesives based on polychloroprene rubber and hybrid acrylic adhesive. The analysis was based on peel, shear and tensile tests for the assemblies on various substrates. Adhesion work was also determined from the contact angles and superficial tensions. The values of the adhesion work confirm the results obtained with the above mentioned tests. Keywords: pressure sensitive adhesives, polychloroprene-based rubber, hybrid acrylic adhesives

This paper has had as purpose rendering of some researches related to extrusion velocities while obtaining multilayer films with five layers of polymer. An installation comprising five extruders has been used for trials and conditions and optimal areas for every single extruder had been set. The results thus obtained made possible to settle the optimum parameters for the extrusion process so that to ensure a stable flow of the molten polymer, which resulted in a uniform multilayer, faultless structural film. Keywords: polyethylene, extrusion, co-extrusion, multilayer film

This article deals with weld quality in reference to strength and seal using in experiment quasi-simultaneous laser thermoplastic welding, method for PA 6.6 GF 35, base material. In laser welding of thermoplastics, sometimes referred to as „laser transmission welding” or „through transmission IR welding (TTIr)”, transparent and absorbing parts are bonded together. The laser beam penetrates the transparent plastic and is converted to heat in the absorbing plastic. Since both parts are pressed together during the welding process, heat is conducted from the absorbing to the transparent plastic, allowing both materials to melt and create a bond. Internal joining pressure is also generated through the local warming and thermal expansion. Almost all thermoplastic materials and elastomeres can be welded with the LASER beam – including ABS, PA, PC, PP, PMMA, PS, PBT, as well as glass fibre reinforced plastics. The strength of the welding seam is comparable with the base material strength. Keywords: laser thermoplastic welding, transparent plastic, internal joining

Using environmentally friendly products in the roads construction like friendlier warm mix asphalts, involves reducing the temperature of asphalt mixtures manufacturing. For this purpose it is recommended to identify synthetic additives that reduce the temperature of asphalt mixture preparation and therefore energy costs of asphalting process. The waxes presence in conventional bitumen road was considered along time inopportune. Three types of amide waxes were synthesized by treating ethylene diamine with a fatty acid and a dicarboxylic acid. Prepared additives characterization was performed by determining the melting points and thermogravimetric behaviour. Keywords: bitumen, wax additive, catalyst