Browse Articles

The paper presents a methodology devoted to statistical analysis of welding characteristic process parameters in high frequency for Polyvinyl Chloride. The experimental values for technological parameters assure a high stability during the control processes in production as well as a high quality of joint welding. Key words: high frequency, welding, polymers, process

The characterization study of the molecular structure for some Mannich type condensates, obtained by the replacement of the acid catalysis, is presented. The characterization of the condensation products was conducted by IR and MNR spectroscopy. For the amino-salicylic-formaldehide condensate, the possibility to be used as an activating agent on a standard structure of butadienstyrenic rubber reticulated by a classic vulcanization system based on sulphur and sulphenamide was demonstrated. Keywords: Mannich condensates, structural analysis, vulcanization activating agent

In this paper the authors propose a new method to determine the properties of a composite material made from two different components: fiber glass cloth and resin. On the separation surface between the two materials it is assumed that the continuity conditions concerning the tensors of stresses and strains between these two components are totally satisfied. The constitutive equations were determined for each material as functions of these components with respect to a local system of reference. Medium stresses and strains were defined in order to establish the properties of the material as a whole. Considering the interdependence existing at the level of those properties the constitutive equations of the composite have been found. Mathematical expressions for elastic modulus and Poisson’s ratio have been also determined. A loading with forces applied on a longitudinal as well on a perpendicular direction face to the fibers direction of the composite is considered. We find out that the elastic properties along the fibers of the composite are closer to the properties of the reinforcing fibers and the elastic properties perpendicular to the fibers of the composite are closer to the matrix properties. Keywords: composite, elastic properties, constitutive equations

Two new polymeric materials were prepared by coating of polyurethane (PU) with a collagen (COL) gel and a mixture of collagen-elastin (COL/EL). The bioactivated polymeric materials were examined by scanning electron microscopy (SEM) for pore morphology. They were also comparatively assayed for porosity, mechanical properties and biodegradability in the presence of bacterial collagenase. In vitro biocompatibility studies were performed in a primary culture of human dermal fibroblasts using spectrophotometric and light microscopy methods. These new polymeric materials showed good tensile strength, biodegradability and a high in vitro biocompatibility. They can be used in the field of medical devices where such physical and biological features are necessary. Key words: polyurethane, natural polymers, collagen, elastin, biocompatibility, biodegradability

Ultraviolet and heat-curable polyurethane acrylate prepolymers were synthesized from 4,4’-diphenyl methane diisocyanate, polyethylene adipate diol, polyhexamethylene carbonate diol, polycaprolactone diol and 1,6- hexamethylene diamine , acrylic acid. Effects of nature of the soft segments on the physical properties were investigated. It was found that the thermal stability increased from polycarbonate diol to polyester diol. Tensile modulus and strength decreased for polyurethane acrylate based poly (ethylene adipate) diol. DSC scans show that all of the model polymers exhibit thermal transitions including a glass transition below –35oC. These soft elastic segment structures, in addition to the physical and chemical cross-linked nature of hard segment, provide enough crosslink sites to have elastomeric behaviour. Keywords: polyurethane acrylate, cross-linked, mechanical properties, thermal behaviour

Present paper refers to the possibility of obtaining nanocomposites through microemulsion copolymerization of butylacrylate (BuA) with vinyltriethoxysilane (VTES), in the absence/presence of some layered silicates. The maximal reaction rates of the BuA/VTES systems, with/without layered silicates, were evaluated through gravimetric technique. The products were characterized by FTIR spectroscopy, TGA and ESEM microscopy. Keywords: microemulsion, layered silicates, sol-gel process

Water soluble polymers can play an important role with regard to the formation and stabilization of particles with diameters in a range from hundred to a few nanometers. Combining the tunability of poly(amidehydroxyurethane) PAmHU as template with the electrochemical reduction of metal precursor in a galvanostatic process have been obtained magnetite and silver nanoparticles with the dimensions varying from 17 to 20 nm and 19 to 21 nm respectively. The analysis of synthesized nanoparticles evidenced that the nanosystems are organized into a coreshell with an inner-core formed from unit cells of metal. Keywords: magnetite and silver nanoparticles, galvanostatic assay synthesis, poly(amidehydroxyurethane) as template, nanomorphological analysis

Mixing and processing characteristics, mechanical and thermal characteristics of MVQ/PP composites were investigated. Both initial and total torque of these materials are increased with increase in the PP concentration of the blend composite. The area under the torque-time curve represents the mechanical energy cosumed during blending. The energy required for blending decreases with increase in MVQ concentration. A lower value for final torque (viscosity) implies better processibility with lower energy consumption during mixing and further processing such as extrusion, calandering and moulding. Also, with the increased PP in blends, some properties such as, hardness, tensile strength and impact strength are increased in blend materials compared to silicone rubber vulcanizate. The heterogenity of MVQ/PP composites was determined by thermomechanical analysis. MVQ and PP show separate Tgs, which indicates that they are not compatible. These characteristic properties (high softening point, high impact strength, easy and low cost processability) indicate that these composites might replace some vulcanized rubbers and some rigid plastics in applications, especially in the automative industry. Keywords: processing, mechanical properties, blend, composites

Reinforced materials and manufacturing procedures have a significant influence on the quality, productivity and competitiveness of polymeric composite structures. The present study aims to highlight the influence of manufacturing procedures and the reinforced material on the mechanical characteristics features resulting from the process of being subjected to traction. Polymeric composite plates reinforced with glass and carbon fiber obtained through hand lay-up, hand lay-up with pressure and vaccum bag molding process. Keywords: polyester resins, epoxy resins, fiber glass, carbon fiber, composite materials

iPP/TiO2 samples containing various amount of nanofiller (5, 10, 15, 20 and 30 %) are investigated in the g - radiation field. Thermal stability and electrical properties (permittivity, dielectric loss and volume resistivity) were assessed for the evaluation of the effects of compounding on the functional performances of basis polymer material. The improvement in the thermal stability has been emphasized. The correlation between the presence of TiO2 nanoparticles at various levels of concentration and electrical behavior is discussed. Keywords: polypropylene, nanocomposite, titania, functional performances