Volume 49, Issue 1

Abstract: In the present study EP142-C510-50 woven carbon fiber composite was investigated from structural/mechanical point of view aiming manufacturing parts for aeronautical industry. The composites were obtained by hand lay-up process. Prior to mechanical tests, the cure reaction results of composite resins specimens were analyzed by using DSC technique. The EP142 epoxy matrix was cured/polymerized at 160°C. After molding, the laminates were cut into specimens for 3 points flexure, tensile and fatigue tests. The mechanical tested samples observed by scanning electron microscopy revealed their fractured and microstructure aspects. A nondestructive US method allowing elastic constant determination on a composite plate was proposed during this study. Keywords: carbon/epoxy composite material, mechanical properties, structural characterization, aeronautical industry

Abstract: The options to deposit chemically a functional composite copper-diamond coatings from trilonic electrolyte have been studied with respect to the influence of the air flow stiring conditions of deposition. They have been elucidated in regard to the structure of the copper metal-matrix and the number of the co-deposited diamond particles. Optimal composition has been established as well as the best hydrodynamic regime for chemical deposition of the functional composite copper-diamond coatings (with respect to the number of the co-deposited diamond particles observed by SEM and the thickness of the composite layer) upon the addition of an appropriate surfactant compound Na-laurylsulfonate (NaLS) to the electrolyte, which is preventing the agglomeration and precipitation of the diamond particles in the electrolyte. Keywords: functional composites; coating; metal-matrix composites (MMCs); non-metallic substrate

Abstract: The surface effect of nano- and microscale structures of some orthopedic materials, containing nano hydroxyapatite (HAP) and collagen type I (COL), on the interactions of osteoblasts with the surface of these materials is investigated and analyzed. The size and shape of inorganic particles are examined by TEM, SEM and AFM imaging. The surface morphology of collagen self-assemblies is also explored by AFM and SEM observations. Results show that the effect of the surface structure is significant on cell behaviour and can be correlated with cell constructs on these materials in cell culture. Keywords: orthopedic materials, surface structure, osteoblasts, TEM, SEM, AFM

Abstract: The paper deals with a comparison of the surface roughness of WPC (Wood Plastic Composite) after the machining (turning). Turning was performed with constant speed rotation and constant depth of cut. The goal of this paper was the observed change of average maximum height Rz (roughness average Ra) with change of feeds (interval of feed f=0.1 to 0.61mm) and design recommendations resulting from acquired knowledge. Keywords: Wood Plastic Composite, machining, surface roughness

Abstract: Polymeric fixed partial prosthesis represents an important part of the prosthetic treatment. Their presence in the oral cavity could lead to fracture them and to alter the final prosthetic treatment. Time Domain Optical Coherence Tomography can be used as a noninvasive evaluation method and 3D reconstructions which could generate a real forecast on those prosthesis in the oral cavity environment. Keywords: polymeric fixed partial prosthesis, optical coherence tomography, non invasive method, material defect

Abstract: This paper refers to the preparation of durable performance concrete using superplasticizer additives. The study revealed the influence of polymer additives on the nature and concentration of physical and mechanical characteristics of concrete obtained as compared with a standard concrete (without additives). Keywords: concrete, polymeric additives, superplasticizers, lignosulfonates, ether polycarboxylates

Abstract: The paper focuses on the experimental evaluation of acoustic properties of biodegradable composite materials with textile inserts used for products with a protective role in the urban habitat. The materials used in this study are obtained from mixed wood and textile waste bonded together with ecological binders. In order to determine the absorption and reflection coefficients, the samples were tested using the impedance tube Bruel & Kjaer type, 4206 A, with a frequency range between 100 - 3200 Hz. It was concluded that the tested specimens have shown a high absorption coefficient for the frequency range between 800 – 2800 Hz. It was also noticed that the values of absorption coefficient depended on the type and quantity of binders. Based on the experimental results, the composition of the tested materials will be improved in the future in order to obtain a good absorption of the sound at low frequencies. Keywords: absorption, reflection, composite, frequency, impedance tube

Abstract: Engineers, biologists and surgeons face a special task when they design procedures, components and systems to replace tissues damaged beyond any limits, caused by disease or trauma. It has been proven that titanium and its alloys have an excellent biocompatibility, that’s why many studies have been made on them, in order to enhance their biomedical applicability. In this paper, the wear behavior of HEMA was analyzed, for use as a cartilage substitute , in experimental models in vivo for testing under conditions very close to reality for two new materials, Ti12Mo and Ti25Nb25Ta alloys. Keywords: titanium alloy, synovial fluid, HEMA

Abstract: The role of the concentration of the components of the alkaline electrolyte for chemical (electroless) coating of cobalt has been investigated with respect to the rate of their deposition on flexible organic support (polyterephthalate). It has been proved that with the increase in the concentration of Co2+ ions in the solution the rate of deposition is growing up. The influence of the concentration of NaH2PO2, used as a reducing agent, has been studied in regard to the kinetics of deposition and with respect to the morphology of the cobalt coating, as well as the effect on the quantity of the phosphorus co-deposited in the coating. In the course of the study on the influence of the buffering components (NH4Cl and H3BO3) in the working electrolyte, preventing the undesired liberation of cobalt hydroxide, on the kinetics of reduction of the cobalt ions, their optimal concentrations have been ascertained. It has been found that the increase in pH and in the temperature of the studied electrolyte determined an increase in the rate of reduction of the cobalt ions, whereupon the optimal values have been selected. Keywords: chemical deposition, cobalt, coating, organic substrate

Abstract: In this study, the chemical modification reaction of polystyrene (PS) with maleic anhydride (MA) in the presence of borontrifluoride (BF3) catalyst in chloroform was examined. The modified polystyrene containing (-COCH=CHCOOH) fragments in phenyl rings was characterized by IR and 1H-NMR spectroscopy. In addition, TGA, AFM analyses and contact-angles for polystyrene and the modified polystyrene were performed. The effects of polystyrene concentration, maleic anhydride concentration, catalyst concentration, solvent volume and temperature on the modification reaction were investigated by determining the amount of the carboxyl group fixed to the aromatic ring of polystyrene. Some kinetic parameters such as the reaction rate, the rate constant, the activation energy for the modification reaction were calculated. Keywords: polystyrene, maleic anhydride, chemical modification, reaction kinetics

Abstract: 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

Abstract: The aim of the present study was to synthesize and characterize some bioconjugated systems based on dendritic polymers and paclitaxel. Three types of polyamidoamine dendrimers (PAMAM) with amine terminated groups and different generations (PAMAM-G1-NH2, PAMAM-G4- NH2, PAMAM-G6-NH2) were used as polymeric hosts. The bioconjugated systems were characterized using FT-IR Spectroscopy and thermogravimetrical analysis. Keywords: dendrimers, paclitaxel, FTIR spectroscopy

Abstract: The objective of this paper was to review the acrylic based resins biodegradation phenomena. The general objectives are based on multidisciplinary research of biomaterials used in dental medicine. For this analysis, different types of polymers were evaluated for water absorption and mechanical strength degradation caused by exposure to saliva. Two sets of 10 specimens were prepared from the analyzed materials according to manufacturer recommendations. The mechanical properties determined on wet samples were lower than those of samples from the same materials, tested dry. Difference between the mechanical properties determined in wet and dry was higher for those materials in which the degree of water absorption was higher. This indicates a clear influence of saliva on the biodegradation of these materials. Key words: dental polymer, mechanical properties, saliva

Abstract: This paper presents the results of the experimental researches regarding the influence of the composition of some film-forming polymeric products for the protection of concrete on certain of their characteristics. Thus, there have come into prominence the film-forming products based on acrylic resins with superior characteristics by comparison to the film-forming products based on acrylic-styrene resins. Keywords: film-forming product, acrylic polymers, concrete, covering system, acrylic-styrene polymers