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Photochromic properties of copolyethers and copolyesters based on bisphenol-A 4,4’-dihydroxydiphenyl, 4, 4’-dihydroxy-azobenzene and 3,3-bis (chloromethyl) oxetane both embedded in a polymer matrix [polymethyl metha crylate (PMMA), polyxinil alchol (PVA)] and the pure state, deposed on quartz disks or as powder, have been studied. The photocromic effects have been studied by means of electronic absorption spectra in visible range. This effect is reversible. A general characteristic of the compounds studied in this paper is that the azobenzene groups belonging to the polymer chain are aligned along the polymer chain structure. The nature of the thermally stimulated discharge current for polyether and polyester samples in the temperature range from room temperature to above glass-rubber transition temperature of the studied compounds, with crystallinity degree of about 0.45, is analyzed. Processing the experimental data according to the Gauss’ function (1) has lead to a good agreement between them and the dipolar polarization model that uses the Langevin’s function, L(b) (2). The thermally stimulated current spectrum of the studied compounds shows two peaks at a temperature about 330 and 3444 K. The a peak is at temperature ( 323 –333)K and r peak at (340-355) K. The disorientation of the main chain dipoles (diazo groups) and the realizing of the trapped electrons are probably responsible for the a peak. The changes in the r peak is caused by carries of charges generated in the polar groups of the polymer chain by the thermochromic effect of the diazobenzen groups.

By exposure to the environment of polymer wastes, the disintegration and degradation processes take place by simultaneous and concurrent mechanisms, as photodegradation, hydrolisys, thermooxidation and biodegradation. The latter may be described as a complex process taking place in several steps. In a first step of the biodegradation process, the polymer with low molecular mass suffer a hydrolisys reaction enzymatically catalyzed, resulting in a mixture of oligomers and intermediates with low molecular mass and different chemical structures. The next step is preceded by microorganisms invasion, transforming the carbon and the hydrogen of polymers and respective intermediates into CO2 and H2O. In the study there are presented some reaction and initiation mechanisms of the biodegradation processes of some synthetic polymers susceptible to biodegradation.

In this paper a relaxation model for polymeric materials is presented.

The copolymerization of octamethylcyclotetrasiloxane and methylhydrogensiloxane oligomers was carried out using a styrene-divinylbenzene copolymer with sulphonic groups as catalyst (VIONIT CS-34C). The conversion versus time function was studied at different temperatures. It was found a first order reaction towards monomers.

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