Volume 51, Issue 1

Abstract: The paper focuses on the development of composite materials based on bacterial cellulose and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV). Natural composites were obtained from bacterial cellulose membranes and chloroform copolyester solutions (various mass ratios). The composite membranes were characterized by FT-IR spectroscopy, X-ray diffraction, SEM morphology, contact angle measurements and thermogravimetric analysis. Cellulose nanofibrils coating and/or precipitation with PHBHV particles was observed. The biocompatibility of composite materials was assessed by using L929 mouse fibroblast cells monolayers. Possible applications of these composite materials are focused on blood vessel engineering and/or wound dressing management. Keywords: bacterial cellulose, polyhydroxyalkanoates, composites, tissue engineering

Abstract: Bimetallic Pd-Ag nanoparticles (NPs) were obtained by polyol method in the presence of poly (vinylpyrrolidone), PVP, as capping agent. The reduction of silver and palladium precursors was performed in argon inert atmosphere by successive reduction, or coreduction approach. In the successive reduction, AgNO3 solution was injected in the ethylene glycol solution of PVP at 140°C, followed by the injection of [Pd(NH3)4]Cl2 solution. The obtained bimetallic Pd-Ag NPs exhibited cluster structure, with the surface reach in silver. The NPs size was in the range of 30 – 58.5 nm with the average dimention of 41.5 nm. The coreduction approach consists in the hot injection of both metal precursors as complex ammine dissolved in ethylene glycol. By this method, smaller Pd-Ag NPs with the average sizes in the range 16 – 30 nm were obtained, depending on the synthesis parameters. The influence of metal cations : PVP molar ratio, metal cations concentration, Ag : Pd atomic ratio and the reduction temperature on the composition and morphology of the bimetallic NPs was studied. For both reduction approaches, based on the experimental data, two different reduction patways were proposed. Keywords: bimetallic nanoparticles, Ag, Pd, PVP, polyol method, coreduction, successive reduction

Abstract: This study was focused on the synthesis of some new hybrid materials based on poly(amidoamine) dendrimer and halloysite designed for 5-Fluorouracil encapsulation. Different techniques like Spectroscopic methods (FTIR, XPS and UV-Vis) and thermogravimetric analysis were used to characterize the hybrid materials. The morphology of the hybrid materials was pointed out using Scanning Electron Microscopy ( SEM) analysis. The obtained results showed that the drug encapsulation efficiency of the hybrid materials was strongly influenced by the interactions between dendrimer-halloysite and drug molecules. Keywords: dendrimer, halloysite, 5-fluorouracil, UV-Vis, X-Ray Photoelectron Spectroscopy

Abstract: Direct photoreduction and photosensitization are powerful approaches for the in-situ synthesis in a polymer matrix. A silver–acrylate nanocomposite was prepared using a novel one-pot strategy involving simultaneous photoinduced reduction and free radical polymerization processes. The fabrication of metal nanocomposite was performed using an acrylate functionalized oligomer (polyethylene glycol 600 diacrylate) and a silver salt (AgNO3). The formation of Ag-nanoparticles was followed by UV–Vis spectroscopy which shows a surface plasmon band at a wavelength range between 410 and 440 nm. Transmission electron microscopy revealed that the synthesized nanoparticles were spherical in shape with a diameter between 5 to 20 nm. The polymerization process was followed quantitatively by infrared spectroscopy, monitoring the disappearance of the characteristic bands for the acrylate double bonds (1410 cm-1). The optimum conditions for obtaining the silver-polymer nanocomposites have been determined (silver precursor concentration, molar ratio silver precursor/photoinitiator, irradiation time and intensity). A reaction mechanism was proposed to explain the polymerization rate dependence on the silver cations content. Keywords: Silver nanoparticles, photo polymerization, acrylate, nanocomposites

Abstract: In this paper, data on Melana-type polyacrylonitrile fibres dyeing with Crystal violet (CV) - triphenylmethane dye- in the presence of maleic acid copolymers with vinyl acetate (NaM-VA) or styrene (NaM-S) are presented. Mathematical models of the studied dyeing processes have been developed and the necessary information on their significant factors is produced by means of experiment planning methods, known as Design of Experiment (DoE) or Experimental design. Optimal correlations between the application conditions and the colour differences obtained on Melana-type fibre have also been studied. Keywords: Melana fiber, Maleic copolymers, Crystal violet dye, Color differences, Statistic modeling, Optimization process

Abstract: Difficulty to objectively determine the moment of bone fracture consolidation by classical imaging methods makes necessary the development of a method that will allow establishing, by objective criteria, the moment in which biomechanical loading of the injured bone segment may be permitted. We propose a method based on the approximation between bone diaphysis and a beam, analysing its behaviour under frequency excitation at one end and measuring the vibrations at the other end. Variation of parameters measured in the structurally sound structures compared to the fractured ones, as well as the possibility to analyse their evolution in the presence of osteosynthesis materials used for the surgical treatment of fractures is ascertained. The existence of composite plastic materials of which the used anatomical bone mould for this experiment is made simulates the real pathological situation, which allows extending the determinations to clinical cases. Key words: bone, fracture, mould, polyurethane, osteosynthesis material, composite material

Abstract: The paper presents a comparative analysis between the performances of pressure sensitive adhesives based on polychloroprene rubber and hybrid acrylic adhesive. The analysis was based on peel, shear and tensile tests for the assemblies on various substrates. Adhesion work was also determined from the contact angles and superficial tensions. The values of the adhesion work confirm the results obtained with the above mentioned tests. Keywords: pressure sensitive adhesives, polychloroprene-based rubber, hybrid acrylic adhesives

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: 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

Abstract: The paper presents the results by application of one method to study the behaviour of packaging material in contact with food products, using different type of adhesives and different types of films for the package manufacturing. The presented method is based on primary aromatic amine determination using spectrophotometer analyze. Three different types of adhesives and three types of different films were considered for testing the migration of aromatic amines. The test was made in the same conditions for each product. Results are used for selecting optimum for material and technology in packaging of food and drinks products by multi-layer lamination in flexible approach. Key words: packaging material, adhesives, migration limit, aromatic amines, food products

Abstract: Currently the leather industry has to face very high costs to treat and eliminate wastes. Therefore, the aim is to treat organic waste (protein and cellulose) by biochemical processes in order to be recycled in industry and agriculture. All treatments applied to waste mainly aim at substantially reducing environmental pollution. Worldwide research on leather recycling is directed towards obtaining protein composites by biochemical treatments using microorganisms/enzymes and obtaining protein hydrolysates and protein binders with different uses. Leather, even in the form of waste, is a valuable protein source for many areas: leather industry, automotive industry, agriculture, animal husbandry, pharmaceuticals, cosmetics, etc. Organic biopolymers are a source of raw materials for agriculture, as protein waste composition provides sufficient elements to improve the composition of and remediate degraded soils, and plants can benefit from elements such as nitrogen, calcium, magnesium, sodium, potassium, etc. This paper presents a new pilot-scale technology for biochemical hydrolysis of tannery waste and obtaining protein biocomposites - multicomponent systems of protein and cellulose biopolymers with application in the footwear industry and in agriculture for the remediation of degraded soils. Keywords: biotechnology, protein wastes, cellulose, biopolymer, tannery

Abstract: The paper presents a study about obtaining materials with prolonged biocidal effect based on styrene-butadiene block-copolymers (SBS) grafted with methacrylic acid (ACM) and coupled with antibiotics from the ampicillin group. The IR spectroscopy and the elemental analysis were used to confirm the structure of SBS block-copolymers grafted with methacrylic acid and of the medical ones. The content of grafted methacrylic acid was about 18.8 % in accordance with the 1,2 enchained butadiene content, proving that the methacrylation polymer-analogous reaction takes place at these pendant vinyl groups of the polybutadiene chain. The concentration of the methacrylic acid-ampicillin pendant group is about 38 % and corresponds to the theoretical calculated one. The antibacterial testing of the synthesized polymers showed that the final reaction product has a relatively high biocidal activity on gram-positive and gram-negative microorganisms. Keywords: styrene-butadiene block-copolymers, methacrylic grafting, polymer with antibiotic effect

Abstract: In this paper we study the non-uniformity that appears in the composite bars reinforced with fiber glass fabric. We defined a factor which characterizes the non-uniformity from the composite materials. We will give a formula for calculating this coefficient and a formula for the elasticity modulus of the composite bars, with two zones in which the volumetric proportions of reinforcement are different. We compared the theoretical results, which give the values of the uniformity coefficient and elasticity modulus, with experimental results obtained for three sets of samples made from ambresit and reinforced with fiber glass fabric. Keywords: composite materials, non-uniformity coefficient, elasticity modulus

Abstract: Over the last years the use of bioabsorbable materials in orthopaedic surgery has increased exponentially. One of the first surgical interventions to take benefit from these absorbable materials was the reconstructive surgery for the anterior cruciate ligament (ACL) of the knee, meaning the use of interference screws for the primary fixation of the ligament graft. The aim of this paper is to present the main types of screws of this kind, used in current practice, the preferred manufacturing materials and to evaluate the standard implantation procedures in terms of the stability they ensure to the ligament graft. Keywords: bioabsorbable screws, ACL reconstruction, ligamentoplasty

Abstract: The present study pursues the influence of polyelectrolytes based on maleic co-polymers with styrene and vinyl acetate under the form of natrium salt, on the colour parameters CIEL*a*b* of the Melana type polyacrylonitrile fibers dyed with Methylene blue. The work is part of a study on the metachromacy of cationic dyestuffs at dyeing the polyacrylonitrile fibres in the presence of cationic polyelectrolytes. The colours attributes are analyzed in terms of the tinctorial conditions: polyelectrolyte character and concentration, dyeing temperature and during time. Keywords: maleic polyelectrolytes, polyacrylonitrile fibres, colour differences, tinctorial parameters, methylene Blue

Abstract: The introduction of the thermo and fotopolymerizable acrylic resins for the manufacture of total prostheses base has revolutionized dentistry in the 20th century. Thermopolymerizable acrylic resins (methacrylic acid derivatives) are found to have a low degree of toxicity on oral tissues after resection of the lower facial floor. It raises the question of thermo and fotopolimerizable acrylic resins toxicity compared with transplanted tissues from outside the oral cavity, in these cases compared with free osseomiocutaneous fibular flap. With the help of these resins, the restoration of the mastication, swallowing, phonation and physiognomy functions was achieved. The impact of free flaps in reconstruction of the mandible and oral floor and osseointegration of dental implants ensuring the stability of dentures are remarkable, allowing the reconstruction of the lower facial floor in a very high degree and the restoration of all functions. Keywords: acrilic resins, reconstruction lower floor