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Natural polymers, or polymers derived from living creatures, are of great interest in the biomaterials field. Collagen is the most widely found protein in mammals (25% of our total protein mass!) and is the major provider of strength to tissue. The paper presents a study regarding obtaining and characterization of biocomposite based on vinyl-acrylic copolymers as latexes and collagen polypeptides, in the following variants: blends, intermolecular complexes and interpenetrated polymeric structures. The present work discusses the results obtained on the rheological behaviour of the fluid mixtures. Regression analysis of the experimental rheological data illustrates that the latex of vinyl-acrylic copolymer is characterized by a second-order polynomial model, while the composites including collagen hydrolysates are preferentially fitted with third-order polynomial model. It has been proved the influence of the molecular weight and the concentration of collagen hydrolysate aqueous solutions on the viscosity and flowing index of polymer mixture in fluid state. Keywords: biocomposite, collagen, blends, acrylic biopolymer

The paper presents the technological steps to obtain new electrodes, made by Cu-Zn alloy, coated with one flux layer, which may be used to welding-brazing of thin plates from ferritic steels, with applications in automotive industry. The experiments realised for elements casting, was made on induction furnace, and the production technology of experimental batch for flux coated electrodes, begins with the elaboration of the alloy and his casting. The obtained electrodes have low production costs and good welding properties. Keywords: electrodes, welding-brazing; flux; galvanized steel

The dimensional changes of the materials used for bite registrations are critical for the accuracy of the records meant for programming the dental articulators. The purpose of this study was to determine the long-term dimensional changes of three bite registration materials. We selected two polyvinyl siloxanes and a bis acrylate-based material. The study was carried out in a semi-adjustable articulator. The data were collected by a photo camera in standardized conditions and then analyzed using an appropriate program and statistical analysis. We did not find significant long-term dimensional changes of the used materials. In the limits of this study we concluded that the polyvinyl siloxane, as well as the bis acrylate based bite registration materials are accurate enough to provide reliable records to program the semi-adjustable articulators. Keywords: polyvinyl siloxane, bis acrylate, bite registration, dimensional changes

In this work the properties of PDLC film based on block copolymer film are presented. The FTIR; phase transition temperature properties are studied in order to see the absorption of block copolymer with the LC. Optical microscopic work showed the increase in droplet size with the increase in block copolymer contents. It is found absorption of block copolymer does not increase linearly with the increase in its contents. Moreover a decrease in refractive index is observed with the increase in block copolymer contents. The decrease in refractive index of block copolymer with temperature is interesting for thermo-optical and electro-optical devices simultaneously. Keywords: Polymer Dispersed Liquid Crystal (PDLC); Phase separation; Liquid Crystal (LC): FTIR spectroscopy

In Pediatric practical dentistry, beside the great variety of direct dental restoration materials the dentist must take into account several factors such as morpho-structural particularities of temporary teeth, the clinical situation, physician performance, behavioural features of children and last but not least the quality of the chosen material. Thus, we investigated the behavior of glass ionomers cements in occlusal stress by determining their mechanical properties. The study aims to determine the vertical compressive strength values, which is one of the mechanical properties of filling materials, the strength of materials being useful in the research of occlusal forces exerted on the future restorations. We had used two glass ionomer cements and a resin modified glass ionomer cement, which then we have tested them to obtain comparative data of the resistance for vertical compression. Keywords: glass ionomers cements, mechanical properties, vertical compression, temporary teeth

The computerized technologies and equipment for obtaining nanofibers impose high training, a large interdisciplinary substantiation, capacity for data storage, memorizing, easy usage, selectivity, fiability, stability, reduced time for analizing / processing of the technological parameters. That is why the computerized electrospinning equipment and technologies for obtaining nanofibers are possible candidates to carry out these requirements owing to the fact that they present both the proper selectivity / sensibility and the increased processing /determining /intervening speed by using the computerized control. This paper aims to present the operation and aplication of equipment for obtaining polimeric nanofibers by electrospinning technology. The designing and accomplishing of the suggested electrospinning equipment has been aimed to obtain a modular system which should allow the control of the technological parameters by means of the computer. Thus, the multitude of the parameters which influence the process of electrospinning, can be independently and automatically varied. The obtained nanofibers were studied by scanning electron microscope. Keywords: nanofibers, equipment, technology, modular conception, electrospinning

Plastination suits very good for 3D reconstruction and morphometric measurements. Digital representation of anatomical features has provided a useful source of data for computer-based instructional development. The validation of 3D reconstructions and measurements needs a thoroughly knowledge about shrinkage. The aim of this paper is to determine the average slice shrinkage rate occurring during sheet plastination (E12 and P40). Fresh human brain slices for P40, pelvis slices for the standard E12 technique and a shoulder tissue block for the E12 thin slice technique were used for this study. In order to determine the shrinkage rate, the slice areas were measured before and after plastination for al samples. For the E12 thin slice technique, the shoulder tissue block was measured before and after plastination and a volumetric shrinkage rate was determined. The shrinkage rate was for P 40 technique 5.74%, for standard E12 technique 6.54% and for the E12 thin slices technique 6.23%. Therefore, plastinated slices showed a decreased shrinkage rate and fit best for research purposes. All shrinkage rates were under 10%, so we believe that every shrinkage below this value is appropriate and actually is fitted for a correct plastination procedure. Keywords: plastination, polymer E12, polymer P40, shrinkage

The surgical approach of the skull base pathology is in a state of constant development. The advancement of the ablative techniques forced the development in the field of reconstructive surgery of the skull base as well. The goal of the reconstructive surgery of the postablative defect of the skull base is to create a stable, watertight limit between the endocranian and the sinusal cavities. New reconstructive materials and adhesives were developed. The purpose of this article is to critically analyze the use of the mixture between the polyethylene glycol ester and trilysine amine solution as a sealant and adhesive in the reconstructive surgery of the skull base. Keywords: polyethylene glycol ester, trilysine amine solution, skull base, reconstructive surgery

Statistical copolymers N-isopropylacrylamide (NIPAM) – 5,6-benzo-2-methylene-1,3-dioxepane (BMDO) with different compositions were prepared by RAFT polymerization and characterized by 1H NMR, GPC and DSC analyses. Their solid-state thermal degradation was investigated for the first time by TGA, showing that the presence of the BMDO units within the PNIPAM chain decreased the thermal stability of the copolymer. In the case of higher BMDO content copolymers the onset decomposition temperature was lower even than that of PBMDO, and also a multistep decomposition process was noticed. The evolution of the global activation energy of the degradation process as a function of degradation conversion was determined by means of the Kissinger-Akahira-Sunose isoconversional method. Keywords: N-isopropylacrylamide; 5,6-benzo-2-methylene-1,3-dioxepane; copolymer; thermosensitive; thermal degradation; Kissinger-Akahira-Sunose isoconversional method

Many studies are concerning with impact properties of composite materials because their large usage in aero-spatial, automotive, marine and sport industry. As the use of composites is continuously increasing the need for more valuable materials becomes essential in designing and producing such materials for a growing market. It is well known that thermoplastic matrix composites show better impact resistance than the thermoset matrix materials but their forming technology is more expensive. This study was designed to analyse the impact behaviour of fabric reinforced thermoset polymer matrix composites with an emphasis on structure of reinforcement. The matrix is an epoxy resin (Epiphen RE4020 – DE 4020, Bostik) while the used fabrics are of carbon fibres, aramid, fibres and glass fibres. Low velocity tests were performed on materials, according to ISO N-6603, and the results were inspected by tomography. Keywords: epoxy resin, fabrics, impact tests