Volume 45, Issue 3

Abstract: The paper shows a series of data concerning the formation and lignin nature of polymeric deposits built up at the beechwood pre-hydrolysis. By means of elemental compostion, data limit formulas (empiric) of deposits have been calculated also emphasizing the special influence of hidromodule over the structure of deposits. The second part of the paper shows aspects related to the recovery of lignin polymeric deposits in order to synthetize a lignin-phenol-formladehyde resin, useful to the wood processing sector as well as the energy sector. Keywords: pre-hydrolysis, beech, limit formulas (empiric), lignin-phenol-formaldehyde resins

Abstract: Functional polyamides with hydroxyl pendant groups were prepared by the direct polycondensation of 5,5`-methylene-bissalicylic acid, with various diamines (p-phenylenediamine, 4,4’-oxydianiline and 4,4’-methylenedianiline) in N-methyl-2-pyrrolidone, using triphenyl phosphite and pyridine as condensing agents. The resulting polymers were chemically modified with 4-maleimidobenzoyl chloride, resulting in polyamides with maleimide pendant groups. The polymer structures were confirmed by elemental analysis data and spectroscopic (IR, 1H-NMR) characterizations. Their inherent viscosities were in the range of 0.22 to 0.34 dlg-1. The polymers were soluble in dipolar aprotic solvents such as dimethylsulfoxide, dimethylformamide, and were thermally stable up to 314 °C. The chemically modified polyamides exhibited better solubility and thermal stability than their unmodified counterparts. Keywords: polyamide, maleimide, Yamazaki-Higashi polycondensation, reactive polymers

Abstract: The aim of the present work is to investigate the effect of different stress levels on the creep and recovery behaviour of polymer-matrix composites. Four hours creep followed by two hours recovery tests were performed to woven GFRP specimens at five different stress levels corresponding to five different percentages of ultimate static strength. Since the behaviour was linear viscoelastic, a four element viscoelastic model was applied. In addition, the viscoelastic behaviour observed was correlated with the degree of damage generated due to creep and its variation with the applied stress levels. Keywords: creep, recovery, linear viscoelastic behaviour, four parameter model

Abstract: Ultrasonic waveform is one of the parameters that characterize a material.Thus, in this paper, the authors aim to visualize and characterize different waveforms of a POLYPROPENE FOIL F-401. The experiment is made with non contact transducers (the resonance frequency is 50 MHz) by applying the method through transmission. There are determined the acoustical and spectral parameters such as the propagation velocity, the time of the flight of the ultrasound, the pulse width, the bandwidth, the peak frequency and its amplitude. The waveform without the sample beeing placed between the transducers (transmitter-receiver) is considered to be the reference. Then, the sample is placed between the transducers at different distances from the transmitter. These waveforms are compared and analysed relative to the reference. Keywords:ultrasounds, non-contact transducers, polymers, ultrasounds waveforms

Abstract: A series of poly(maleic anhydride-alt-vinyl acetate) conjugates with alkylating agents were evaluated regarding antitumoral activity, biodistribution and organotropic effects. The synthesized conjugates exhibits a significant antitumoral activity expressed as ATR (average tumor retention). In addition the obtained macromolecular compounds show a prolonged half-life in sanguine serum and accumulation in tumoral tissue. The last effect is supposed to be enhanced by EPR (enhanced permeation and retention) effect. The analyzed compounds also exhibit some organotropic effects such as the increase of liver, spleen and kidney weight. The LD50 values of the alkylating agents and conjugated ones proved that the coupling reaction decrease the intrinsic toxicity of the alkylating agents. Keywords: poly(maleic anhydride-alt-vinyl acetate), antitumoral activity, EPR effect

Abstract: New chemically modified polysulphones with both N-phenacyl-4, 4’-bipyridinium bromide and N-alkylacetate-4, 4’-bipyridinium bromide derivatives, have been synthesized by chemical modification reaction of chloromethylated polysulphones with various N-substituted monoquaternary-4, 4’-bipyridinium bromides. The structure of the modified polysulphones was confirmed by elemental analysis and 1H-NMR spectroscopy. Various reaction conditions were checked in view to obtain soluble polymers. Key words: chemically modified polysulphone, chloromethylated polysulphone, N-phenacyl-4, 4’-bipyridinium bromide, N-alkylacetate-4, 4’-bipyridinium bromide, viologen

Abstract: Composite materials are sometimes harder to machine than metals, because they are anisotropic, not homogenous and their reinforcing fibers are very abrasive. Significant damage to the work piece may be introduced and high wear rates of the tools are experienced while machining. A presentation of the data obtained through experiments and an analysis of the drilling moments when machining composites will be made in this article. Keywords: the polymeric composite materials, cutting, drilling moments

Abstract: The paper presents the parameters of the ultrasonic welding process of some combinations of materials. These parameters can be divided intro three categories: technological, mechanical and acoustical. A particular attention has to be paid to the technological and acoustical parameters, since they influence the quality of the welds. Keywords: welding horn, energy director, near field, far field, static force

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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