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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

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

Both the theoretic elements of an interferometric method for the refractive index determination based on a Fabry-Perot etalon and the procedure of the Fabry-Perot cell obtaining are described in this paper. The results obtained by this method for PVA isotropic foils and for PVA foils including small amounts of potassium iodide are given here. Keywords: PVA, FPE, refractive index, isotropic materials

Full denture casting currently represents a technological alternative. The casting system we tested usually uses reversible hydrocolloids for investing wax patterns. Besides the system’s own advantages, the authors also noticed certain errors consecutive to casting, materialized in lack of substance and the development of porosities on the mucosal facets of the complete denture bases. Keywords: casting, full dentures, errors

The aim of the experimental study described in this paper was Lamb wave method evaluation for damage/defects detection of epoxi/glass composites. Can be used piezoelectric transducers - actuator/sensor - glued on the surface of investigated composite, using transmission mode. The chosen control parameter was the sensor signal attenuation because of defects that exists in examinated samples. The proposed monitoring system was efficiently in the detection of damage/defects such as holes, allowing for damage/defect size estimation. Keywords: composites damages detection, Lamb wave

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

The objective of this study is to compare the results obtained while determining the amount of residual monomer in three samples of acrylic resin in the first 24 hours after getting done the prostheses in the dental lab with the results of patch-tests performed on three subjects, after they have worn dentures for three months. Keywords: patch-test, acrylic resin, residual monomer, allergenic potential

The epoxy resin EPO 99B, known under the name REZOLIN, is one of the main materials used in manufacturing/modeling the axial runner of hydraulic machines. The simplest device of this kind is the inducer employed to reduce the cavitation intensity of the main pump impeller. The geometry is determined from hydrodynamic conditions, is a very complex one and is subjected to dynamic mechanical stress (vibrations). As a result of those conditions the resin must have good mechanical and technological qualities. It was realized at SC Elba SA Timisoara, and is made from a mixture between the resin H9951 and a fortifier. The obtained inducer runners have been tested in air at the Hydraulic Machinery Laboratory of Timisoara Polytechnic University, and supplementary the basic material was tasted to cavitation erosion resistance. As a result, our work takes into considerations both the impeller hydrodynamic performances and the behaviour of the manufacturing material (resin EPO 99 B) to cavitation erosion. Key words: epoxy resin, cavitation erosion of plastic material, inducer runner performances

This paper presents some morphological properties of polyamide 6 thin films obtained by spin-coating method. These properties were investigated by scanning electron microscopy and atomic force microscopy. It results that the thin film thickness is influenced both by rotation speed and solution concentration. Finally, some aspects between morphological and optical properties (structural colours) were considered. Key words: polyamide thin films, spin-coating method, scanning and atomic force microscopy, structural

Poly(betaine)s based on poly(N-vinylimidazole) (PNVI) and poly(4-vinylpyridine) (P4VP), namely poly(carboxybetaine)s with one (PNVIB-1 and P4VPB-1) and two (PNVIB-2 and P4VPB-2) methylene groups between the opposite charges were prepared. Poly(betaine)s represent high dipolar materials with wide spectrum of unique and specific properties. Some of such properties are shown in this paper. Thus, the PNVIB-1 and P4VPB-1 are insoluble in water but the addition of salts promotes their solubility, whereas PNVIB-2 and P4VPB-2 are soluble both water and aqueous solution of salts as well as in methanol. Also, for all the polybetaines one of the most interesting properties in solid state is the formation of homogeneous blends with some inorganic salts in equimolecular amounts, they being a new type of organic-inorganic hybrid materials. Keywords: poly(carboxybetaine)s, anti-polyelectrolyte behaviour, poly(zwitterions), organic-inorganic hybrids