Browse Articles

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

Guardrails are systems designed to keep vehicles in certain places, by preventing access in dangerous areas. They can be a source of injuries because their rigid structure, designed to face high level of strength. Depending on their speed and mass, vehicles can load guardrails in various forms. The authors propose the use of adaptive guardrails, involving polymers, which react different by different load levels. The behaviour is studied using modeling and simulation with the FEM; different types of guardrails and external loads displacement and stress are presented, as support to choose the most convenient type of guardrail for each application. Keywords: adaptive guardrails, traffic security, polymers, FEM simulation

Inexpensive plastic covered greenhouse structures of the type used by the horticulture industry for plant production are frequently used. We have developed “selective film” with the following properties: transmit the visible light portion of the solar radiation spectrum, the only portion utilized by plants for photosynthesis; absorb the small amount of ultraviolet radiation in the spectrum and cause some of it to fluoresce into visible light, useful to plants, absorb infrared radiation , which plants cannot use and which cause greenhouse interiors to overheat. Plant growth inside the experimental greenhouses covered with photoselective films were compared with plants grown inside growth chambers covered with clear conventional greenhouse films. The results are summarized in the paper. Keywords : greenhouses, photoselective film, plasticulture, solar radiation

The kinetics of the equilibrium anionic polymerization of some cyclic siloxanes is modelled by using neural networks. Feedforward neural networks with one or two hidden layers have been used to appreciate the rates of disappearance of octamethylcyclotetrasiloxane and aminopropyl disiloxane at different catalyst concentrations (direct modelling). Alternatively, another neural model has been developed to estimate the amount of catalyst, which leads to an imposed final concentration of siloxane (inverse modelling). Experimental data for the polymerization of octamethylcyclotetrasiloxane in the presence of KOH as a catalyst and 1,3-bis(aminopropyl)tetramethyldisiloxane as a functional endblocker were used as training data sets for neural models. Satisfactory agreement between experimental data and network predictions obtained in validation phases proved that the projected models have good generalization capacities and, consequently, they describe well the process. Keywords: neural networks, direct and inverse neural modelling, polysiloxane, cyclic siloxanes, anionic ring opening polymerization

This paper presents a monitoring methodology of the processing temperature for the polymeric composite materials. An experimental stand was realized consisting of a computer with an acquisition card and the LabVIEW software that allows the real time monitoring of the composite materials temperature during the processing through the aid of a new heat sensor LM 335Z. This digital sensor had proved to be more efficient than the classical thermo-couplings. Using the LabVIEW software, a virtual instrument called “Virtual Thermometer” was created. This virtual instrument has the same functions as a real instrument, but with a much more complexity as well as the possibility of real time measuring, save, analysis and presentation of the collected data. Keywords: monitoring, polymeric composites, virtual instrument

In this paper the linear polymers transport through a nanopore is simulated. The major effects of superimposed electric field and the monomers number on the polymer translocation have been proved. The polymer escape time is inversely proportional with the electric field’s intensity and directly proportional with the polymer’s length. Keywords: transport phenomena, Langevin equation, nanometer pore, translocation time

In this paper the calculation methods of the demolding force in case of thin-wall injected plastic parts with linear, curvilinear or combined profile are presented. The magnitude of this force directly influences the constructive solution of the ejector system. Key words: injected part, demolding force, ejector system