Browse Articles

The present paper aims to present a method for redesigning plastic products using the Reverse Engineering technique. The originality of this paper stems from its integration of modern scanning techniques and reverse engineering with traditional manufacturing techniques. The paper presents a case study about the redesign of an existing product for which no technical documentation is available, using three distinct phases: reverse engineering, modeling analysis and redesign, manufacturing and testing.. Keywords: redesign, reverse engineering, mould, polymeric material

This study presents new findings of the water/ethanol (ratio) influence on the aniline hydrochloride polymerization process in presence of ammonium persulfate. Water/ethanol mixtures in presence of monomer hydrochloride, as proved by the conductometric, spectrophotometric and refractometric investigations, are far from ideal solutions and promote a partitioned environment , for the polymerization process. By controlling this key parameter (water/ethanol ratio) the polymerization can be shifted from a initial dispersion process to a solution one, followed by precipitation. The associated phenomena revealed modification in terms of conversion, structure (FTIR, UV-VIS), morphology (SEM), thermal stability and doping agent retention (TGA-DTG). Keywords: conductive polymers, aniline hydrochloride, water/ethanol system, polyaniline

The options to deposit chemically a functional composite copper-diamond coating from trilonic electrolyte have been studied with respect to textile polyethylene terephthalate substrate. The optimal basic composition of the electrolyte for surface treatment and the optimal conditions of deposition has been found from the viewpoint of the deposition rate, respectively the thickness of qualitative layer of the copper matrix. A systematic study of the influence of different types and concentrations of surface active agents (SAA) and different temperatures of the electrolyte at continuous air flow stiring has been realized, aimed co-deposition of copper metal-matrix composite, containing diamond particles (sizes, varying within the range 3-70mm). Keywords: coating; fabrics/textiles; surface treatments; metal-matrix composites (MMCs); functional composites

In this article, some advantages and disadvantages of the incorporation method of azobenzene moieties in several polymer matrices (polymethacrylate, poly(styrene-alt-maleimide), poly(oxazoline-co-methacrylate), poly(methacrylate-co-methacryloxypropyl trimethoxy-silane)) are highlighted. Their physical properties (molecular weights, glass transition temperatures, chromophore load, solubility, and solvatochromism) are discussed with regard to their macromolecular architecture. Solvent effect on the UV-Vis absorption spectra of azo-polymers was investigated using Reichardt’s solvent polarity scale and Kamlet-Taft multiparameter equation. Kamlet-Taft equation revealed that hydrogen bond acceptor properties and dipolarity/polarizability of the solvent have a significant contribution upon the solvatochromic behaviour of azopolymers. Keywords: azobenzene, side-chain polymers, solvatochromism, Kamlet-Taft equation

A series of six new experimental light-curing dental composites based on two Bis-GMA-type oligomers, quartz and nano-fluorohydroxyapatite (nano-FHAP), in different ratios, were prepared. The paper refers to the characterization of organic and inorganic phases from the uncured composite pastes and determination of the properties of the light-cured composite materials. Differential scanning calorimetry was used to measure the heat of polymerization of the monomer mixtures. Investigation of nano-FHAP was made by transmission electron microscopy TEMBF, HRTEM and X-ray diffraction. The mechanical strengths, water sorption and solubility were determined. We came to the conclusion that for the same monomer mixture, the water sorption and solubility values increased with the content of nano-FHAP in the composite material, but there remained in the limits of ISO 4049/2000 for the compositions comprising up to 50% nano-FHAP in the filler. The highest mechanical strengths were obtained in the case of composites containing 75% quartz in the filler. Keywords: dental nanocomposites, extent of polymerization, mechanical properties, water sorption, solubility

Fibre Reinforced Polymers (FRP) confinements on square and rectangular sections behave differently from confined circular sections. Confining inward pressure over the entire circular section is uniform, whereas in non-circular sections confining pressure development is inconsistent. As a result, these sections could be divided into the distinct properly and partially confined areas. Presence of these partially confined regions would much reduce influence of FRP confinements to increase concrete’s peak strength and ultimate strain. To evaluate confinement effectiveness, effect of mentioned areas must be taken into account precisely. This paper describes a theoretical model adapted to seismic strengthening and retrofit of the square section RC columns confined with advanced composite materials. The model is the author’s earlier proposed one calibrated with cautious survey on the existing test data. This model takes into account geometrical parameters of the column shape such as overlapping length and corner rounding radius; furthermore both concrete and FRP confinement mechanical properties. Finally it proposes a new shape factor for the square sections which plays a major role in effectiveness evaluation of FRP confinement. Keywords: Fibre Reinforced Polymers, square section, Reinforced Concrete columns, strengthening

Lignin, a natural renewable material, was incorporated in a series of polydimethylsiloxane/silica composites. Besides the effect as bulk filler, the presence of lignin determines the change of some properties among them being surface properties that were evaluated by contact angle and water sorption measurements. The contact angles were determined in static regime by using the sessile drop technique. Dynamic water vapour sorption was applied to register the sorption/desorption isotherms and kinetic curves. The sorption type and maximum vapour sorption capacity were evaluated based on these data. The results were correlated with the composition of the prepared materials. Keywords: surface properties; siloxanes; composites; lignin

Organic biopolymers are a source of raw material for agriculture, whereas the composition of protein wastes provides sufficient elements to improve the composition and remediation of degraded soils and plants by exploiting elements, such as nitrogen, calcium, magnesium, sodium, potassium etc. From processing one tone of raw hide, 75% is discarded, of which 50% could be further used as organic fertilizer. Protein biopolymers were obtained by means of an innovative enzymatic procedure for waste processing. In combination with polyacrylamide, acrylic, maleic, cellulose, starch etc. are used in the agricultural field. We characterize the protein biopolymers by specific morpho-structural analysis methods (UV-Vis, IR spectroscopy, thermal analyses, X-ray diffraction, microscopy).The novelty of this work is the biochemical combination process of synthetic polymers with organic biopolymers from tanneries with viable and interesting applications in agriculture. Keywords: biopolymer, protein wastes, tannery, soil, structural analysis

Functionalized dental implants represent an advanced approaching in implantology, aiming to improve the biointegration and the long-term success of surgical procedures. In this article are reported the synthesis of hydroxyapatite (HA) and Poly(methyl methacrylate) (PMMA) thin films on metallic substrates – used as dental implant-type structures – by pulsed laser deposition (PLD) method. Plasma and plume evolution of ablated HA and PMMA species was registered through optical analyze by fast CCD camera. Numerical simulation performed using a simple hydrodynamic model properly reproduce this type of plasma behaviour. SEM-EDAX measurements were performed assessing the apatitic-type structure of the prepared films along with their satisfactory mechanical adhesion. Keywords: synthetic polymer, pulsed laser deposition, hydrodynamic model

The use of the acrylic resins in the dental technique was a very important gain for the manufacturing and treatment of dentures and during the years new materials and technologies have appeared on the market, promising a better quality. Full-denture casting currently represents a technological alternative. The casting system we tested usually uses reversible hydrocolloids for investing wax patterns, and has certain advantages. Thermoplastic materials are used more and more widely in the technology of complete or removable partial dentures due to their superior qualities. Thermoplastic resins are suitable for manufacturing a wide range of removable partial dentures without metallic structure, in optimal conditions of biocompatibility, by injection. Our aim is to compare thermopolimerysable acrylic resins, manufactured using the classic technology with cast full dentures and injected thermoplastic resins. Keywords: thermopolimerisable acrylic resin, thermoplastic resin, molding-injection devices, casting, full dentures