Volume 40, Issue 3

Abstract: The kinetic approach on thermal stabilization of LDPE in the presence of 7 chalcone compounds is presented. The application of zero order or first order treatment to the experimental date obtained for stabilized LDPE has revealed that the depletion of antioxidant is a first order process. The comparison of the most efficient member of chalcone series and some commercial phenolic antioxidants has provided the following sequence for the prevention of oxidation: ETANOX – 330 ] D4 ] IRGANOX – 1076 ] CYANOX – 2246 ] TOPANOL – OC ]] purified LDPE

Abstract: Rheological behaviour of some products based on chemical modified starch, with characteristics proper to retarding additives for concrete designed for cementation of the big depth wells, was investigated. With that end in view, rheological tests of several pastes obtained from products of the hydroxypropylstarch type were carried out. Maintaining, at pastes preparation, the concentration of 10% additive, proved as being the most efficient in use, shearing strain tests were performed at 20°C, 40°C and 60°C versus keeping time of pastes, namely, 24 h and 48 h from preparation time. At the same time, influence of the disodicphosphate and urea additions over rheological pastes was investigated versus the same parameters. Based on the experimental results obtained, the mathematical models describing rheological behaviour of the tested additives, within a large range of external stress and temperature, were elaborated.

Abstract: This paper presents data concerning the capacity of a bismaleinimide (BMI) to protect elastomers with different structures and unsaturated degree and the copolymers EVA submitted to thermooxidative destruction at 80 - 200ºC. The main structural changes were followed in the IR domain and the kinetic parameters of the processes were determined.

Abstract: The research investigated the compatibility between the styrene-butadiene rubber mix and wastage materials of finite cromated leather in order to obtain products necessary in various industries or specifically in the leather and shoes industry. The researchers immersed multiple composite samples containing rubber and various proportions of leather-wastage in three solvents: benzene,carbon-tetrachloride and cloroform. The samples where then monitored during their expansion in time and the changes that occurred in the IR spectra. The studies have demonstrated the material compatibility confirmed also by mechano-physical determinations.

Abstract: Five commercial products, based on acrylic polymers, have been used for cotton coating. The structures of the polymers have been established based on their IR spectra of the active compound from the acrylic dispersion. The properties of the coated materials have been discussed in connection with the structure of the acrylic polymer.

Abstract: New poly(succinimide-ether)s with maleimidic rings in the side chain were synthesized by a chemical modification reaction on the polymers containing hydroxylic pendant groups. The polymers were obtained in good yields and they were characterized by elemental analysis, infrared and proton nuclear magnetic resonance spectroscopy, gel permeation chromatography, dynamic thermogravimetric analysis and solution viscometry.

Abstract: Coating powders are finely grounded polymeric materials containing binders, pigments, extenders and special additives, used to obtain decorative and protective organic coatings. There are two major categories: thermoplastic and thermoreactive coating powders, based on thermoplastic and on thermoreactive binders, respectively. This paper presents the classes of thermoplastic coating powders, and their main characteristics.

Abstract: The canning of fuel elements in nuclear reactors is subjected to stress and strains, which may cause failure if the material does not possess sufficient ductility. Of particular interest is localized strain in the circumferential or transverse ductility. The ring expansion test has been used for the determination of what has been called the transverse ductility of fuel element cladding. However, after some thought, it is realized that the ductility determined in this test does not really represent the determination in a fuel pin. In this paper some results, which serve to illustrate the limits of the test to rank materials, have been discussed.

Abstract: In this study were investigated the thermal and mechanical behavior of some polyurethane ignites by addition with nonreactive flame-retardants. Some flame-retardants, such as the compounds containing halogen, give toxic and corrosive fumes during combustion. To prevent these problems, non-halogenated flame-retardants, such as phosphorus-containing compounds, are materials of choice. The polyurethane elastomers were prepared using dibenzyldiisocyanate (DBDI) as isocyanate, poly(ethylene-adipate)diol (PEA) as polyol, diethylehe glycol (DEG), hexanediol (HD) or 1,4-butanediol (BD) as chain extenders, and different amounts of tris(1,3-dichloro-propyl-phosphat) (TDP). In some cases, to be improved the flame resistance was used small amounts of antimony trioxide (Sb2O3), which act as a “synergistic effect”. The polyurethane ignites were characterized by thermogravimetric analysis (TGA), elemental analysis and stress-strain measurements which were performed on a TIRAtest 2161 apparatus (Germany), equipped with a 100N cell and an extension rate of 10 mm/min. The hardness measurements were effectuated on disc with an apparatus standardized in grade Shore A (oSh A).

Abstract: Synthesis of orto- and para-aminobenzoic groups grafted on copolymers is described. The method is applied, extended and optimised for gel-type styrene-divinylbenzene copolymers (S-DVB) with „5` and „7` degree of crosslinking.

Abstract: 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.