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This work presents a study on the interaction that a phenolic hindered antioxidant (Irganox-1076) and new reactive dyes derivated from 3H-aza-1-oxa-2H-thioxo-5,8-phenalendisulphonic acids, have upon izopolipropylene thermooxidation. The study was performed by chemiluminescence technique (CL). Synergetic effects were observed between reactive dyes used and phenolic antioxidant in thermooxidation protection of the polymer.

The paper shows and analyzes the results of some researches on a plastic composite material as fiberglass reinforced polyester (FGRP) that is considered for being used for manufacturing the blades of small power wind turbines, such is the 5 kW wind turbine from Ciugud site in Alba County, Romania. During their operation the wind turbine blades are continuously subject to variable loadings developed by the stochastic and uncontrollable wind flow. Consequently has been performed mechanical strength researches done on a real blade, as well as, by lab testing on test specimens sampled from the original material of one blade tested at SC CLAGI Srl Company. The results of this research work came to confirm the quality of the FGRP used for blade fabrication, as well as, its capacity to bear well the loads and implicitly the structural stresses produced by the wind upon the wind turbine blades, although a metallic reinforcement included within the inner part enhances the whole mechanical strength of the blade structure. Keywords: fiberglass reinforced polyester (FGRP), wind turbine, aerodynamic forces, loads, stresses, mechanical strength

In this paper, some models for gel and glass effects – a new empirical model and Chiu’s model – are checked under batch and semibatch, isothermal and nonisothermal reaction conditions. The chemical initiated free radical polymerization of methyl methacrylate is considered to be achieved in a bulk process and the reaction mechanism takes into account the azobisisobutyronitrile decomposition, propagation, chain transfer to monomer and termination by disproportionation. In the exponential relations that represent the dependence of termination and propagation rate constants on monomer conversion (gel and glass effects), the coefficients are polynomials of forth degree in temperature. For batch operating conditions, the simulations performed at different temperatures and initiator concentrations give results close to experimental ones. In semibatch operation, an instantaneous addition of initiator at different reaction times and different temperatures was considered. Step changes in temperature performed at different reaction times represent an other type of operation taken into account in this paper. In the semibatch and nonisothermal reaction conditions, the simulation results of the two models agree with experimental data even if the same values of parameters as for batch isothermal operation were used. This paper demonstrates the generality of the exponential models and also emphasizes the possibility of controlling polymer properties and reaction time by semibatch and nonisothermal operations.

An aromatic photosensitive polyimide is prepared from 3,3`,4,4`-benzophenone tetracarboxylic dianhydride and 4,4`-diaminodiphenyl methane and its structuring ability upon UV-laser exposure is investigated. Surface modification is performed at two laser fluences, i.e. 89 and 244 mJ/cm2, and different number of pulses. The changes of the surface morphology, induced by the employed patterning technique, are examined. According to atomic force microscopy data cone-like structures are formed and their appearance mechanism is analyzed taking into account the laser irradiation conditions. Surface wettability tests reveal an intensification of hydrophobic character, which may be ascribed to the formation of a thin carbon-enriched layer at the polyimide surface. Keywords: polyimide, laser, morphology, wettability

Applications of digital image correlation (DIC) method to material characterisation has been proven to be a powerful tool for deformations and strain analysis and found widespread use and acceptance in the field of experimental mechanics. This paper describes the potential, accuracy and limitations of a commercial DIC system to full-field, real-time characterisation of the coefficient of thermal expansion (CTE) of polymeric materials. The topics such as strain calculation procedure and influence of a small rigid body rotation were theoretically described and experimentally verified. A series of measurements was carried out to determine the CTE polypropylene (PP) and polyvinylchloride (PVC) commercial plastics. To check the feasibility of the method an aluminium sample was initially analysed. The measuring set-up developed includes a simple heating device, thermal sensors and a thermo-camera for real-time temperature measurement and monitoring of the sample and a 3D-DIC measuring system. The results revealed that the DIC can be a reliable tool for thermal deformations measurement especially suitable for polymeric materials with a higher CTE. Keywords: digital image correlation, thermal strains, polymeric materials

Photosensitive polymers based on polysiloxanes substituted with different azo and quaternary ammonium groups were synthesized and characterized. The chemical structure of the synthesized polymers was confirmed using 1H-NMR spectroscopy. The photochromic behaviour was evaluated as a result of the interaction with UV light. The micellar aggregation/disaggregation capacity of the polymers was investigated using fluorescence spectroscopy and dynamic light scattering techniques. All the synthesized amphiphilic polymers are able to generate micelles, the critical concentration of aggregation values being situated in the domain (3-13) x 10-3 g/L. The morphology of the micellar aggregates is fundamentally influenced by the polymer chemical structure. If in the case of azobenzene and azo-5-crwon-15-ether groups it is possible to obtain 35-155 nm diameter individual micelles, for the azo-6-crown-18-ether group, only small aggregates with diameters below 10 nm can be obtained. The micelle’s disaggregation capacity as a consequence of UV irradiation is strongly affected by the hydrophilic/hydrophobic ratio, as well as the chemical structure of the azo groups. Keywords: azobenzene, polysiloxane, photosensitive micelles

By skilful combination between polythiophene backbones and poly(ethylene glycol) (PEG) side chains of different lengths, amphiphilic, fluorescent copolymers having branched architecture of “hairy rods” type were obtained by Suzuki polycondensation. Their structural characterization was performed by 1H-NMR, 13C-NMR and FT-IR spectroscopies and thermal behaviour was followed by differential scanning calorimetry (DSC) and thermogravimetrical analysis (TGA). Photophysical properties in aqueous solutions were evaluated using UV-Vis and fluorescence measurements. The amphiphilic nature of the synthesized polythiophenes and the presence of PEG side chains induced the self - dispersability in water, as well as the formation of fluorescent nanoparticles through self-assembling. The size of the nanoparticles in water was assessed by dynamic light scattering (DLS) and atomic force microscopy (AFM) investigations and the effect of incubation time on three cell lines viability was evaluated, as well. Keywords: polythiophenes, nanoparticles, Suzuki polycondensation, “hairy-rods”, self-assembling

Epoxy resin / carbon nanotubes (CNTs) nanocomposites are nowadays intensively studied in order to produce high performance materials with enhanced properties for specific applications in all activity fields, from electronics to automotive and aeronautics. In order to improve the interactions of CNTs with the polymer matrix, a functionalization of CNTs surface is often required. In this work, functionalized CNTs/epoxy nanocomposites were obtained and investigated by thermogravimetric analysis. Non-covalent functionalized CNTs with three types of surfactants were used. Activation energies of the degradation processes were calculated using Kissinger-Akahira-Sunose isoconversional method. The influence of surfactant type, functionalization mode (covalent or non-covalent) and functionalized CNTs content in composite on the activation energy as a function of the degradation conversion degree was studied. Keywords: thermal degradation, isoconversional method, carbon nanotubes

Necuron is a polyurethane material (PUR) that is used for various applications of industry. The use of these materials in industry increased in recent years because of their good mechanical and machinability properties. Good knowledge of the mechanical behaviour of these materials is highly important therefore this work presents the results of tensile tests carried out on four different types of Necuron. The twenty-eight specimens used were divided in two categories: one without defects and one with defects of two types. Results show that Necuron 1020 is the stiffest material, whereas Necuron 1300 is the strongest. Keywords: tensile testing, necuron, tensile strength, Young’s modulus