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In this paper were investigated influences of various types and concentrations of crosslinking agents on the properties of thermoplastic vulcanizates based on ethylene-propylene terpolymer rubber (EPDM) and plasticized poly (vinyl chloride) (PVC). Three different crosslinking systems were used: (a) common method with sulphur and vulcanization accelerators (tetramethylthiuram disulfide and mercaptobenzothiazole); (b) crosslinking with di(tert-buthyl peroxi-isopropyl) benzene Perkadox 14-40B-GR and co-agent trimethylol-propane trimethacrylate TMPT DL 75 (c) vulcanization with phenol resin Ribetak 75-30E and tin chloride dehydrate. The influence of each crosslinking systems on cross-link density, mechanical properties and DSC analysis of samples were investigated. The hardness shows a slight decrease as a result of dynamic vulcanization, because this is a way to disperse large amounts of elastomer in the thermoplastic matrix, resulting in a refined morphology. It was observed that the highest values of crosslinking density and 100% modulus were obtained by using the classic cross-linking with sulphur and accelerators, and that for a reduced amount of crosslinking agents used, there was a decrease in crosslinking density. Elastomer crosslinking led to an increased Tg and decreased Tm. These blends can be used in the manufacture of hoses, gaskets, footwear constituents etc. Keywords: TPV, EPDM, PVC, cross-link density, differential scanning calorimetry

Acid polyurethane of hard type was prepared to be further treated in hydrothermal conditions at high pressures of 20, 40, 60 and 80 atm. The influence of pressure on chemical structure and morphology of macromolecular chains have been investigated using Fourier transform Infrared Spectroscopy (FT-IR) and Differential Scanning Calorimetry (DSC). Three endothermic peaks appear in hydrothermally treated polyurethanes, being related to conformational changes due to polymer shrinking, decomposition and melting. Their corresponding enthalpies increase with pressure, probably due to a more compact polymer structure at high pressure. Under the influence of pressure, macromolecular chains modify their conformation and approach each other, leading to an increased density of the hydrogen bonds. Stretching vibrations of the –C=O group are shifted from 1746 to 1724 cm-1. There is an optimum pressure (60-80 atm) range where the polyurethane presents an increased capacity of interaction through carbonyl groups (r1 =1.295 at 60 atm) which is favorable for further composite synthesis. Keywords: acid polyurethane, high pressure, hydrothermal process, IR spectroscopy, DSC

The replacement of classical materials used in industry with other more important, cheaper and environment friendly ones and also the prevention of corrosion is one of the goals in the research area. Electrotechnical industry and engineering needs this special material. The conductive and semiconductive coatings belong to these special materials and occupy a large application domain in modern industry, used to remove the electrostatic charges, and for the shielding effects (i.e. Faraday screen, protective coat for the high voltage cables etc.).In this paper it is studied the stability in time of semiconductive lacquers based on polianiline.

This paper presents the radiation stability of epoxy resin modified with different amounts of titania (1, 5 and 10 %). The isothermal chemiluminescence investigation performed at 1500C has pointed out the high radiation stability of investigated systems. The sharp decrease in the early stage of oxidation emphasizes the benefit brought by the filler. Even though the initial chemiluminescence intensity enhances with filler content, the oxidation level after 20 min does not essentially differ. The application of high irradiation doses up to 1000 kGy does not affect the thermal stability of composites. Keywords: radiation stability, epoxy resin, chemiluminescence intensity, filler

The present paper studies the effect of the diameter of single walled carbon nanotubes (SWCNTs) on mechanical properties of SWCNTs reinforced epoxy resin composites. Bulk atomistic models of epoxy resin-SWCNTs with different compositions were built and were subject of an extensive multistage equilibration procedure. Molecular dynamics simulations were used to estimate glass transition temperature (Tg) and Young’s modulus of epoxy resin and epoxy resin/SWCNTs composites. The Young’s moduli generally increased with increasing of SWCNTs content and values range from 1.83 GPa in the case of pure epoxy resins to 3.21 GPa for epoxy resin/SWCNTs (8,8) composite system. Overall, the agreement between predicted values of the material properties and experimental data in the literature is satisfactory. Keywords: atomistic molecular modeling; mechanical properties; SWCNTs- epoxy resin composites, glass transition temperature

This work presents the main mechanical properties of the pressure sensitive adhesives solutions based on carbocatenary elastomers: peel, shear and tensile strength. Polychloroprene rubber was chosen as the main component of the adhesive system and its adhesive performances were evaluated. The mechanisms of fracture of the adhesive bond and breaking at the tensile test were also discussed. Keywords: pressure sensitive, adhesives, elastomers, polychloroprene rubber

This paper presents a study that underlines the importance of the choice of polymer dispersions in the composition of an exterior emulsion paint in order to improve its quality with respect to the action of external factors. All these properties which facilitate the application and increase the durability are due to the homogeneous distribution of inorganic particles in an organic binder. In order to emphasize this influence, various types of polymer latexes were used: a dispersion of an acrylic copolymer and methacrylic ester, but also combinations thereof with a potassium silicate solution, with silicone latex, with a colloidal suspension containing an alkyd resin with 70% solids dissolved in White Spirit, by comparison with a dispersion of nano silica particles in an organic polymer. All these types of paints which were obtained were analyzed by measuring their hardness, contact angle, elasticity, dirt pickup and chalking resistance, color retention during accelerated (artificial) aging, water vapor diffusion and water permeability, thus proving the existence and efficiency of the inorganic particles of the paint composition. Keywords: acrylic dispersion, silicone paints, -acrylic-silicon, solvent based alkyd resins, accelerated aging resistance

Fracture toughness occurring in a material that has micro-cracks may be improved by particle addition, these particles having different properties than the basic material. This paper includes the outcome of a research on the influence of softer or harder particles added to the basic material, on the stresses occurring in the immediate vicinity of micro-cracks. Our research is designed to determine to what extent this process may result into preventing a crack from advancing into the material subject to unfavorable loads, depending on the direction of that crack. The outcome we achieved using finite element analysis supports the assumption that, by adding a certain amount of particles, which have specific characteristics, to the basic material, fracture toughness may increase significantly. Keywords: inclusion, crack, stress, finite element analysis, hard and soft particles

This work reports on a study concerning the behaviour of the reinforced beech beams with CFRP (carbon fiber reinforced plastic) under a bending load. An experimental program was proposed to characterize the strength response of CFRP-wood beams. Mechanical tests on the reinforced wood showed that CFRP materials may produce flexural displacement and lifting increases of the beams. Observations of the experimental load–displacement relationships showed that bending strength increased for wood beams reinforced with CFRP composite plates (Megaplate), compared to those without CFRP reinforcement. Keywords: carbon fiber, bending strength, wood, pretension device

Safety requirements are becoming more and more important in terms of polymers interaction with fire, while various flame retardant additives are being expelled for their adverse effects on the environment. This is the reason for the research challenge for new effective and environmentally friendly flame retardant systems. In this view, the objectives of the present study were the synthesis of the 2,4,6-triiodophenyl acrylate (TIPA) monomer and of p(MMA-co-TIPA) copolymer; and the determination of the reactivity ratios of the comonomers. As foreseen, MMA reactivity is obviously superior to TIPA (r1 = 5.49 and r2 = 0.053), and a decrease of initial copolymerisation rate is noticed as the feed enriches in MMA. Keywords: reactivity ratio, 2,4,6-triiodophenyl acrylate, homopropagation