Browse Articles

This paper has had as purpose rendering of some researches related to extrusion velocities while obtaining multilayer films with five layers of polymer. An installation comprising five extruders has been used for trials and conditions and optimal areas for every single extruder had been set. The results thus obtained made possible to settle the optimum parameters for the extrusion process so that to ensure a stable flow of the molten polymer, which resulted in a uniform multilayer, faultless structural film. Keywords: polyethylene, extrusion, co-extrusion, multilayer film

This article deals with weld quality in reference to strength and seal using in experiment quasi-simultaneous laser thermoplastic welding, method for PA 6.6 GF 35, base material. In laser welding of thermoplastics, sometimes referred to as „laser transmission welding” or „through transmission IR welding (TTIr)”, transparent and absorbing parts are bonded together. The laser beam penetrates the transparent plastic and is converted to heat in the absorbing plastic. Since both parts are pressed together during the welding process, heat is conducted from the absorbing to the transparent plastic, allowing both materials to melt and create a bond. Internal joining pressure is also generated through the local warming and thermal expansion. Almost all thermoplastic materials and elastomeres can be welded with the LASER beam – including ABS, PA, PC, PP, PMMA, PS, PBT, as well as glass fibre reinforced plastics. The strength of the welding seam is comparable with the base material strength. Keywords: laser thermoplastic welding, transparent plastic, internal joining

Using environmentally friendly products in the roads construction like friendlier warm mix asphalts, involves reducing the temperature of asphalt mixtures manufacturing. For this purpose it is recommended to identify synthetic additives that reduce the temperature of asphalt mixture preparation and therefore energy costs of asphalting process. The waxes presence in conventional bitumen road was considered along time inopportune. Three types of amide waxes were synthesized by treating ethylene diamine with a fatty acid and a dicarboxylic acid. Prepared additives characterization was performed by determining the melting points and thermogravimetric behaviour. Keywords: bitumen, wax additive, catalyst

The aim of the present paper was to obtain epoxy nanocomposites reinforced with layered clays type nanofiller. Nanocomposites materials have been obtained through mechanical mixing of resins based on diglycidyl ether of bisphenol A (DGEBA) chemically modified with low molecular glycols filled with Cloisit type layered clays and crosslinked using 4,4 ‘diaminodiphenyl metane ( DDM)as curing agent. Epoxy nanocomposites have been obtained and characterized as compared to standard epoxy nanocomposites not only by conventional methods-physical-mechanical properties, but also by DMA tests in order to establish the degree of dispersion of the nanocaly in the epoxy matrix. Flexural strength and impact tests have shown that the reinforcement of composite materials with laminated clays leads to an improvement in their properties as compared to unmodified epoxy systems. Keywords: epoxy nanocomposite, glass transition, dynamical properties, mechanical properties

Orthodontic appliances are intraoral devices used to induce changes in relations between the teeth and the underlying bone structures. Removable orthodontic appliances, which contribute to the alignment of misaligned teeth and to the development of maxillaries, are not fixed to teeth and can be inserted/removed easily on/off the teeth of the dental arches. The aim of this study was to evaluate some characteristics of removable orthodontic appliances achieved by two different technologies (heat-curing and vacuum-forming), realised by using two dental materials (Superacryl Plus-SpofaDental thermo-cured acrylic resin and Biocryl® C and Biocryl® M -Scheu thermoplastic materials). The study included 123 adolescent patients, to which were manufactured one or two removable orthodontic appliances, on one or both of the dental arches. A total of 141 removable orthodontic appliances were manufactured for the selected adolescent patients. The manufacturing of all types of removable orthodontic appliances followed the same technological procedures, specific to each type of used material. The results of the study demonstrate that the aesthetic effect of the two dental materials presented different results, and the best results were observed at the orthodontic appliances achieved by the vacuum-forming technology, using Biocryl® C and Biocryl® M–Scheu thermoplastic materials. Keywords: removable orthodontic appliances, materials, technologies, aesthetics

Relaxation time reflects dynamic phenomena in the early stages of electrospinning after an abrupt application of an external electric field. Experimental counterpart of relaxation times, i.e., characteristic hydrodynamic times, have been measured using a laboratory device designed especially for this kind of experiments. The experiments supporting the hypothesis are carried out with aqueous solutions of poly (vinyl alcohol) of various concentrations. Experimental data are compared with theoretical predictions of relaxation times aiming to a deeper analysis of dynamic phenomena during the earliest stages of electrospinning. Qualitative and quantitative comparison of theoretical and experimental relaxation times determined that characteristic hydrodynamic times are encouraging. Moreover, the experimental apparatus for characteristic hydrodynamic time investigation revealed regular discharges in a spinning zone of the electro-spinner that imminently precede electrospinning jet appearance. Results of the work contribute to a deeper understanding of a spin-ability of polymeric solutions using electrospinning and are an inspiration for new electrospinning variants. Keywords: nanofibers, needleless electrospinning on the rod, polyvinyl alcohol aqueous solutions, rod, relaxation time

Young’s modulus needed for realizing a numerical analysis model with finite elements dedicated to studying static strain on an artificial bone, made out of composite material (polyester resin reinforced with fiber glass) is determined, as well as Young’s dynamics modulus needed for analysis through numerical simulation of dynamic strain applied to the same structural element (vibrations, shock). Both in, static and dynamic conditions, two methods are utilized in measuring the materials elastic characteristics. Keywords: Young’s modulus, artificial bone, composite material, numerical simulation

The paper presents the obtaining of new biodegradable plastic materials using collagen hydrolysates. As raw materials, to transform into collagen hydrolysates, untanned leathers’ wastes were used. The influence of chemical structure and ratio of protein material on thermoplastic processing were investigated. The effect of protein material contents on physico – mechanical and biodegradability properties has been evidenced. Keywords: biodegradable plastic materials, collagen hydrolysates, protein material

The objective of this study was to obtain graphene oxide starting from graphite and to covalently functionalize this nanomaterial with Cisplatin. The presence of the drug was pointed out using different methods like FTIR Spectroscopy, X-Ray Photoelectron Spectroscopy (XPS), Thermogravimetric analysis (TGA), RAMAN Spectroscopy, X-Ray Diffraction and Scanning electron microscopy (SEM). Keyword: Graphene oxide, covalent activation, Cisplatin

The study was conducted on a powdery mixture derived from mechanical processing of plastics recovered from the instrument panels of ELVs, which contain varying amounts of polypropylene (PP), acrylonitrile butadiene styrene (ABS), polycarbonate (PC),cardboard, rubber, and other materials. The mixture was deposited on a metallic belt-type electrode that introduced them into an area of high intensity electric field created by a rotating cylindrical electrode, connected to a high voltage supply. This electrostatic separation method in association with classical waste processing techniques is a viable solution for the ELVs recycling industry. Keywords: plastic waste, electric fields, electrostatic measurements, electrostatic processes, electrostatic separation