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In this study interpenetrating polymer networks (IPNs) based on bisphenol A diglycidyl dimethacrylate (BisGMA) and diglycidyl ether of bisphenol A (DGEBA) with or without native fumed silica nanoparticles were prepared by in situ polymerization. The properties of the IPNs and hybrid IPNs were evaluated using different thermal techniques as differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermogravimetrical analysis (TGA). The mechanical properties were also determined. Keywords: dimethacrylate, epoxy resin, interpenetrating polymer network, fumed silica

Manufactured in various geometric forms, containing secondary materials (colorants, reinforcements, fireproof etc.), all these make the composites based on resin-textile fibre, basic materials for obtaining lateral walls, ceilings, floors, compartments for luggage and sanitary installations. The materials were made as stratified plates using polyesteric resin POLIKON P210 FA and natural fibres: cotton, flax and hemp. This paper presents the determination of mass and volume content of the resin in these composites.

A laurylsulfate-selective electrode is presented. The sensing material of the electrode consists of an ion pair 1:1 water insoluble salt that has been prepared using sodium laurylsulfate and hexadecyl trimethylammonium bromide and was immobilized in a PVC membrane plasticized with orto-nitrophenyl octyl ether. This electrode gives a linear response for sodium laurylsulfate between 8x10-7 - 5x10-3 M with a slope of 57,7 mV per decade of sodium laurylsulfate concentration. The electrode has been applied to potentiometric titration of anionic surfactant using cationic surfactant as titration agents.

This paper presents a study of the electrical conductivity of wood-polymer composites, determined by measurements done in DC and AC current. It is also noticed that the values of sdc, s’ and s” are strongly influenced by the nature of matrix and filler content of the composite. Finally, it is shown that samples of PE and PP matrices can be used for applications in power frequency electric fields (0 ... 100 Hz) and at temperatures between 30 and 90 °C. Keywords: compozite lemn-polimer, conductivitate electrica

In this paper it is presented a creep model in the theory of viscoelasticity for polymeric materials.

This work brings to the forefront local nonlinear problems that appear in junctions of beam structures made of plastics, subjected to heavy loads. We also revealed the notions of local problems and heavy loads. These theoretical aspects are explained with the help of two beam structures of various complexity, made of plastic, with local problem. The results are presented as stress maps, maps of mechanical strains, charts with the evolution of the states reached in the structure with the loading steps. We mentioned the situations that require local study; nonlinear problems classification is presented and the methodology for nonlinear calculus is described. Keywords: local problem, beam structure, heavy loads, nonlinearity

This paper deals with synthesis and characterization of some copolyamides 6/12 obtained by rotational molding via activated anionic ring–opening copolymerization of e–caprolactam with laurolactam. Sodium bis[(2–metoxyetoxy)e–caprolactam] aluminate, as initiator and N,N’–[methylene–di(1,4–phenylene)bis–carbamoyl]–bis–e–caprolactam, as activator were used. The initial mold temperature (initial polymerization temperature) was kept constant at 160oC. The incorporation of laurolactam into nylon 6 chain depresses both in the degree of crystallinity and the melting temperature of nylon 6/12 copolymers. The notched Izod impact strength of the copolymers increased as the laurolactam content was increased, while the flexural modulus and the water absorption decreased.

The main purposes of this article are: 1) the minimization of an objective multi-criterial function which implies the reaction time, the polidispersion coefficient and the monomer conversion; 2) the obtaining of reaction conditions (temperature and initiator concentration) which determine the realisation of some final imposed values for conversion and polymerization degree. Within the optimization algorythm there were successively considered as decision variables: 1) a single value of temperature (the isothermal case) and the initiator concentration; 2) two temperature levels and the initiator concentration; 3) thee temperature levels. Of the three optimization strategies, the right one was proved to be the temperature trajectory constituted of two values. The obtained optimal politics essentially depend on the objectively chosen function and on the weight factors attached to each interest measure.

The ortocresol, the p-aminophenol and the formaldehyde were taken in different molar ratios and condensed in the presence of hydrocloric acid as catalyst and of toluene) N-methyl pyrolidone mixture as extraction agent of the reaction water. The condensing products are polymers with a low molecular mass, friable solid substances soluble in polar organic solvents which show colors from transparent pink for the ortocresolformaldehidic resin, to dark brown for the p-amino-phenolformaldehidic one. The obtained formaldehidic resins were structurally characterized using IR and 1H-RMN spectroscopy. The thermal properties were also investigated.

This paper presents the performance of two aminic antioxidants (TMQ and PBN) and a phenolic antioxidant (SPH) in formulations based on diene rubbers, typical for tyre treads. An imidazoline was used as secondary accelerator and the influence of antioxidant nature was investigated following its influence on scorch safety, curing behaviour, tensile strength, fatigue behaviour, abrasion performance, and thermo-oxidative degradation.