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The atactic polypropylene (APP) recovery as hydro insulation membranes and / or bitumen presents two main advantages: the great quantities that can be reprocessed and the elevated usage life of the obtained products, a consequence of lack of the photo and thermal degradation during usage. It is well know that the photo and thermal degradation rapidly diminishes the utilization properties, namely the usage life. The recovery into hydro insulation membranes and / or bitumen is possible if the APP was selected based on thermo – oxidative stability criteria typically for a good incorporation into the melt bitumen at 180 0 C for 4 – 10 hours and for RTFOT or TFOT tests. The RTFOT thermo – oxidative stability criterion, according to which the mass loosing at 163 0C for 80 min. must be smaller than 0, 8 %, is fulfilled only if the APP has a weight molecular mass greater than 8000 and a solid consistency. If these two criteria are not fulfilled the APP can be recovered as hot melt adhesives. Keywords: atactic polypropylene, practical application, hydro insulation membranes and bitumen

For the transport of gas or water, it is generally welding by heater which is used for the butting together of the tubes. The quality of the joint is influenced by the choice of the parameters of welding, the geometry of the tubes and the environment. It is not possible of determine analytically the optimal parameters of welding according to dimensions of the tubes. This paper describes the models of extrapolation, which makes it possible to transpose the optimal parameters and strong thickness of welding for tubes of large diameter previously determined using smaller tubes. The first chapter of the paper is primarily centred on an analysis of the process of welding end to end by heater. A mathematic description of the various phases of the process leads to coefficients without dimension. The models used for the determination of the parameters of welding result in the invariance of these coefficients. Keywords: optimization, mathematical model, heated tool butt welding, hydro – carbon (HD-PE), transporting pipelines

We synthesized and characterizated two bromine containing monomers, 2-(2-bromopropyloxy) ethyl methacrylate (BPEM) and 2-(2-bromoisobutyriloxy) ethyl methacrylate (BIEM), to be used as radiopaque agents in acrylic bone cements. Using methyl methacrylate (MMA) and each one of the bromine containing monomers in different concentrations we have synthesized ten copolymers. The copolymerizations were carried out directly in the thermostatic, cell of an NMR Spectrometer. Analyzing the 1H-NMR spectra, we have determined the reactivity ratios of the monomers. Preliminary studies showed that acrylic bone cements which include in the liquid phase these bromine containing acrylic monomers, have a very good radioopacity. Keywords: bromine containing monomers, copolymerization, parameters of reactivity

This article presents literature data regarding the synthesis and properties of some sulfonated aromatic polymers, such as polyethersulfones, poly(etherketone)s, polybenzimidazoles, polyimides, which can be used for proton-exchange membrane in fuel cell applications. The polymers were prepared by two procedures: postsulfonation of existing polymers and direct copolymerization of sulfonated monomers. Some characteristics of the sulfonated polymers in correlation with their structure were also presented. Key words: sulfonation, sulfonated polymers, good solubility, thermal properties

The influence of propylene, polyethylene and maleinized polyethylene on the characteristics of thermoplastic elastomers based on maleinized ethylene-propylene terpolymer rubber was investigated. As the amount of the added polyolefine is increased, the hardness, tensile strength and tear strength increase, and elasticity and elongation at break decrease. The resistance to swelling in toluene and resistance to 50 % nitric acid and 40 % sodium hydroxide are also increased with the increase in the amount of the added polyolefine. The blends containing maleinized PE show higher characteristics than those with PE as such. The rheologic characteristics of the above mentioned blends were studied and compared. The thermoplastic ionic elastomers based on maleinized EPDM and polyolefines can be used in obtaining some materials with specific characteristics (high hardness, tensile strength, elasticity, resistance to acids and alkalis, resistance to swelling in toluene etc.). Key words: polyolefines, maleinized EPDM, thermoplastic ionic elastomer

The paper presents some technological aspects related to a new procedure for centrifugal casting in moulds made of silicone rubber. The procedure has been enhanced by the American company Tekcast Industries Inc. and is applicable for the casting of plastics and metallic alloys of zinc and led, in the case of small production and unique items. Keywords: silicone rubber, centrifugal casting, moulds, zinc alloys

A survay on the radiothermoluminescenceof 25 polymers is presented. The RTL glow curves were recorded on the temperature range starting from 77 K up to room temperature after 60Co irradiation. The most RTL peaks occur at temperatures similar to those assigned to the onset of specific molecular motins, suggesting that the peaks are due to the liberation of electrons from traps formed by the chains of polymer. The RTL glow curves are generally in good agreement with the results reported by other researchers. This paper includes the experimental data obtained from each glow curve (temperature and intensity of maxima). The activation energies of some of the peaks were obtained using several methods. The peaks with lower activation energies generally are located at lower temperatures. Keywords: polymers, elastomers, radiothermoluminescence, characterization, activation energy

In the previous article [1], results concerning the bonding of cured non-polar elastomers supports with adhesive formulations based on non-cured non-polar elastomers have been presented. This research is dedicated to obtain additional information regarding the adhesion mechanism and to study the adhesion strength executed on cured polar elastomers supports with composition based on non-cured polar elastomers. We have used two types of polar cured elastomers basic supports, polychloroprenic rubber and nitrile rubber, and two non-cured adhesive compositions of the same elastomers type. Keywords: adhesives, elastomers, polychloroprene rubber, nitrile rubber

The paper presents the changes in chemical composition and hardness of cylindres used for grinding of rubber wastes. Based on experimental results obtained, some technical solutions can be suggested in order to determine a considerabile growth the life equipment. Keywords: rubber waste grinding

The use of Rapid Prototyping (RP) processes in manufacturing cellular solids offers the advantages of controlling the distribution, dimensions and interconnection of cells, which influence their micro and macro-structural properties. But not all RP processes are able to build cellular solids with closed cells, this article analyzing the capacity of Fused Deposition Modeling (FDM) process to manufacture this type of structures from ABS material. Using a test part containing cubic and spherical cells, it is shown that FDM can manufacture structures with completely enclosed voids, but only for a certain range of dimensions. This approach opens new study directions such as the possibility to analyze the mechanical behaviour of this type of cellular materials with closed cells and controlled geometry, or to use them as test parts for detecting voids in injection moulded parts. Keywords: fused deposition modeling, rapid prototyping, ABS polymer material, cellular solids, closed cells