Volume 43, Issue 3

Abstract: The paperwork presents the principal constituent equations used on study of mincing rubber waste reinforced with metalic insertion. These equations permit a study of mincing process on analytical ground, without being necessary, in some cases, to conduct experimental research. For verifying these equations, an experimental part is presented here, too . A verification of constituent equations can be done. Keywords: rubber wastes, mincing, metalic insertion, modeling equations

Abstract: Hyperbranched poly (e-caprolactone) copolyesters (hb-PCL) have been prepared by combination of ring opening polymerization (ROP) of e-caprolactone (e-CL) as cyclic AB monomer and concurrent polyconden­sation of 2,2´-bis(hydroxymethyl)butyric acid (BHB) as branching AB2 comonomer unit, using a supported lipase (Candida Antarctica Lipase B, CALB; Novozym 435) as catalyst. By systematic variation of the BHB fraction, hyperbranched copolyester samples with systematically varied degrees of branching (DB) have been obtained. 1H-NMR and 13C-NMR spectra provided detailed information on the DBs. Molecular weights for the hb-PCLs were determined by means of SEC and VPO and exhibited a decreasing tendency with increasing fraction of branching comonomer. Thermal properties of the hb-PCL samples were investigated with respect to the DB. As expected, Tm and DHm were found to decrease with increasing content of BHB (DSC). The crystalline morphology of the samples was investigated by WAXS, revealing the DB-dependent existence of two crystalline polymorphs with different density and chain packing. Light microscopy studies demonstrated both a different crystal habitus for the hyperbranched copolymers, as well as a decrease of the crystalline fraction for the hb-PCL samples in comparison to the linear analogue. With increasing DB, the crystallites became small and irregularly shaped, indicating phase segregation in crystallizable and non-crystallizable material during crystallization. Solution viscosimetry showed low specific and intrinsic viscosity for the branched materials and demonstrated that the hyperbranched samples assume an increasingly compact solution structure with increasing extent of branching. For both CHCl3 and THF solutions, an increase of the temperature from 20 to 50oC results in a decrease of [h] for all analyzed hb-PCLs. Keywords: copolyesters, hyperbranched polymers, degree of branching, polymer morphology

Abstract: A recyclable material, that can be incinerated under safety conditions, for humans and environment, the polyvinyl chloride (PVC) is still a largely used polymer, as a compound, inclusively. The PVC -TPU compounds are of interest due to their attrition resistance, chemical resistance, resistance to migration in solvents and oils (low extractibility), high bending under negative temperatures, low densities and erosion, stability to high temperatures, easy processing into finite article, cost efficient. All these properties are superior to a flexible PVC (hot masticated). The paper presents a study on dependency of some usage properties of PVC - TPU compounds on compounds composition. The results of the modification study of PVC with TPU are that new compounds have: the density within the range 1.18 – 1.3 g/cm3 , erosion within the domain 107 – 142 mm3, number of bendings up to breaking at positive temperatures, over 500 000, number of bendings up to cracking at –8 0C, over 500 000 bendings. Keywords: polyvinil chloride, thermoplastic polyurethane, physical modification, abrasion, density

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: Rheological measurements of 3; 6; 10 and 12% INFINEUM SV 260 solutions in SAE 10W mineral oil show non-Newtonian behaviour in the temperature range 313-370 K and shear rates ranging between 3 and 1312 s-1: they follow the Bingham model at low concentrations, low shear rates and high temperatures and the Herschel-Bulkley model at high concentration, high shear rates and low temperatures. KELTAN 4200 solutions in the same solvent are more viscous than the corresponding ones given by INFINEUM SV 260 and follow the Herschel-Bulkley model onto the whole studied concentration, shear rate and temperature ranges. The slopes of the lines representing the variation of log viscosity with the reciprocal of temperature increase slightly with concentration between 3 and 10% for INFINEUM SV 260 solutions and decreases for 12%. The lowest slope is given by 3% solution, followed by 12%, and the highest one by 10% solution. KELTAN 4200 solutions present an increase of slope when passing from 3 to 6% and a decrease when the concentration exceeds the last value. The lowest slope was obtained for 12% solution, followed by 3%, while 6% solution has the highest value. This might suggest that KELTAN 4200 could be a better viscosity improver for the mineral oil SAE 10W, both at low and high concentrations. Keywords: rheological behaviour of concentrated polymer solutions, viscosity improvers, multi-grade oils

Abstract: This paper proposes a genuine mathematical pattern for the study of the unsteady phenomena that characterize the working out of natural gas polyethilene pipeline networks. The calculation programme elaborated on the basis of the mathematical model allows the determination of the period of the two steady regimes between which the unsteady movement takes place, for each pipeline of the network. Keywords: pipeline, natural gas, network, unsteady movement

Abstract: The paper develops a method based on the thermal effects caused by pressure drop, internal friction, external friction and convection, for polymer melts pressure drop calculation in non isothermal melt flow through the channels. The whole thermal effect is equivalent with a supplementary pressure drop Dp (T). Later on Dp (T) generates a supplementary length L (T). This value is added to the initial channel length and an equivalent length, taking into account the thermal effects, Lech , is obtained. By substitution of the length L in isothermal pressure drop relation, with length Lech, the new relations may be applied for non isothermal flow melts. The equivalent length concept is applied to a real case. Keywords: nonisothermal polymer flow, rheology, polymer mold design, polymer melts pressure drop

Abstract: The article presents a study for water vapours permeability and diffusion properties for two hydrophilic materials, used for soft contact lens manufacturing. The materials have been investigated according to DIN 52615, German Standard. The technological advances in obtaining new hydrophilic materials presume a better biocompatibility of these materials and the comfort of the patient. In this way, our study advances an investigation for the microporous hydrophilic materials, to compare their functional properties. Keywords: water vapours permeability, diffusion properties, hydrophilic materials

Abstract: In order to test the presence of some chemical substances within the composition of specific liquids and fluids, such as cosmetics, beverages, hydraulic oil, it is absolutely necessary to measure the foam level as a quality condition for selling them on the market. The paper deals with designing an original device for measuring the foam level, which has the following main components: a mechanical subassembly for positioning the sensors, a closed volume with a propeller subassembly for mixing the liquid and the PC controller. We recommend the use of Thermo-Russel sensors, taking into account the accuracy of the final results. Electrical micro actuators, such as brushless electrical micromotors, are used for actuating the mechanical components. The designed device may have the following original features: the electro-mechanical positioning system for sensors and propeller in the way regarding the increasing of the positioning accuracy of the sensors; the possibility of having different rotational speed of the propeller, as function of liquid viscosity. Taking into account that the foam level could be rapidly destroyed, so that the process time should be over 0.1 s, the device might be controlled either by microcontrollers or by a PC with data acquisition boards. Knowing that the creep of the propeller is altering the measuring final results by reducing the speed of the liquid, the paper presents the tridimensional model of the propeller and its translational displacements using the finite elemet method. Keywords: modelling, simulation, generating wet foam into liquids, measurement

Abstract: This paper contains the results of an experimental research regarding the synthesis of some types of thermoplastic polyurethane based on 1,6-hexanedyol polyadipate (PAH), 1,4-buthanedyol and ethyleneglycol polyadipate (PABE) and ethyleneglycol polyadipate (PAE) and pure 4,4’-diphenyl-methane-diisocyanate (pure MDI). The thermoplastic polyurethanes were physically and mechanically characterized by observing the characteristics variation mode after the synthesis and also after their processing by dissolution and squeeze for the obtaining of marks with preordained properties. Keywords: polyester, di-isocianate, thermoplastic polyuretane, physical-mechanical properties

Abstract: Atom transfer radical polymerization (ATRP) is one of the most versatile controlled/living radical polymerization (CLRP) method for the production of well-defined materials. As a consequence, ATRP has been employed for the synthesis of a large variety of materials, e. g. end-functional oligomers (telechelics, macromonomers), copolymers (statistical, gradient, block, graft, brush, star), hyperbrached polymers, organic - inorganic hybrids (organic - inorganic block and graft copolymers, polymer - layered silicate nanocomposites and polymer - grafted nanoparticles and flat surfaces), etc. The present paper briefly reviews these ATRP applications, in completion to the previous article dealing with ATRP fundamentals [1]. Keywords: atom transfer radical polymerization, block copolymers, graft copolymers, end-functional oligomers, organic-inorganic hybrids