Browse Articles

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

This paper outlines the results of a series of experiments designed and conducted by the authors in order to determine the mechanical properties of a new composite material used for manufacturing the sleeves for the consolidation or reinforcement of the zones with local surface defects (flaws) in transport pipelines. The analysis and interpretation of the results allowed the authors to: assess the effectiveness of the new composite in repairing pipelines with local metal loss defects; establish the most effective way of preparing the pipeline surface for the application of the new composite sleeve; and to emphasize the correlation between the elastic properties of composites and the consolidation or reinforcement effect on the corroded or damaged pipelines following the application of composite sleeves. Keywords: pipeline maintenance, composite sleeve or wrap, mechanical properties of composites

The paper proposes a way of using of the recycled rubber for the manufacturing of a hybrid composite material based on epoxy resin, reinforced both with glass woven fabrics and with recycled rubber. One presents the mechanical characteristics of this composite material, measured in: flexural test by using the method of the three points and impact testing with Charpy pendulum. The work also describes some aspects concerning to the effects of the water absorption on the mechanical behaviour in flexural testing after 2980 h (124 days) of immersion in water, at room temperature. Finally, the experimental results obtained were comparatively analysed for both the dried and wet specimens. One could remark a degradation of the mechanical characteristics (elastic modulus E, flexural strength s, mechanical work W until the maximum force). Concerning the impact behaviour, it was measured the failure energy U and then computed the resilience K (impact strength). It was observed that additionally reinforcing with rubber particles leads to the increasing of the resilience K. Keywords: hybrid composite; recycled rubber; absorption; bending; impact

The plastics components of a random sample of waste electrical and electronic equipment (WEEE) from small household appliances were identified and sorted. Moreover, by taking into account the practical needs for applications demanding medium to less severe restrictions from the standpoint of end-use characteristics, the mechanical and thermal properties are investigated for the four most used plastics in the EU, including acrylonitrile-butadiene-styrene (ABS), styrene-acrylonitrile (SAN), polystyrene (PS) and polypropylene (PP), as well as for a mixture resulting on the basis of corresponding EEE market evaluations. The obtained results show that in the case of these materials, separated prior to processing, even if a minor decrease arises from the standpoint of thermal properties due to inherent degradation induced by processing, the problem is the decline of different mechanical properties. In fact, this appears to be the net result of different morphologies of components – the essentially amorphous-like nature of ABS, SAN and PS, and the semi-crystalline component (PP). Accordingly, the loss in mechanical properties was lower for the elastic modulus, higher in case of impact strength and intermediate for the tensile strength, when the components and the resulting blend properties are compared. Keywords: WEEE, plastics, recycling, thermal properties, mechanical properties