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The aim of this work is to obtain and characterize some collagen/hydroxyapatite composite materials obtained by collagen matrix immersion in SBF, for different immersion times. The obtained composite materials were characterize by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy detector (EDS) and complex thermal analysis. The main differences between the composites obtained by different immersion times can be visualized by SEM images. The increasing immersion time lead to a more compact composite material, with lower porosity as exhibited in the recorded SEM images. On the other hand, not only the morphology is changed but also the composition of the composites. At high immersion time, onto the composite materials, sodium chloride (NaCl) crystals can be observed. The presence of NaCl can be easily identified by XRD and, based on the relative characteristic peaks intensity can be quantified. Keywords: SBF immersion, collagen matrix mineralization, morphological changes versus immersion time

When making a denture, a removable partial prosthesis or a removable orthodontic appliance, long term preservation of structure and function require that potential irritating effects are kept at minimum. Polymer manufacturing technology with optimal properties and the material type are essential for a successful treatment. Increasing the biomechanical comportment of polymeric materials implies fiber reinforcing. The different fibers reinforcing products made very difficult the evaluation of their performances and biomechanical properties analysis. The aim of this study was to assess the quality of various polymeric materials used in dental technology and to validate the en face OCT defectoscopic evaluation of polymeric dental prostheses by using scanning electron microscopy (SEM). SEM investigations evidenced the nonlinear aspect of the interface between the polymeric material and the fiber reinforcement and materials defects in some samples. The advantages of the OCT method consist in non-invasiveness and high resolution. In addition, en face OCT investigations permit visualization of the more complex stratified structure at the interface between the polymeric material and the fiber reinforcement. Keywords: polymeric materials, defectoscopy, en face optical coherence tomography, scanning electron microscopy

This paper presents a failure model applicable for unidirectional fibers reinforced composites that point out the fiber-matrix interface role in the mechanics of the failure process. The model is applicable in any plane stress state case. The ABAQUS/Standard finite elements program is used to point out the applicability of failure model. The deformation of a square plate with the dimensions of 100x100 mm, having a hole with the diameter of 50 mm in the middle, was analyzed. The plate is realized from composite materials with unidirectional fibers oriented at an angle of 45o. The visualization and the interpretation of the simulation results have been made with the help of ABAQUS/Viewer module. The obtained diagrams reflect a very good concordance between the predictions of the failure model and the results provided by other models. This confirms the hypothesis on whose basis the unidirectional composite failure model was formulated. Keywords: composite materials, failure, unidirectional fiber glass, polyester resin

In this paper, we obtained experimentally the elasticity modulus and tensile strength, for four types of composite materials made of epoxy resin reinforced with wheat straw, with different spatial orientation for reinforced. Using experimental results, we have obtained the original formulas, for the calculus of tensile strength and elasticity modulus, for the types of specified materials. These relationships are dependent on the percentage of fibers oriented in the direction of request, and which have the length equal with the test sample. In the case in which the percentage is equal to unit, the relations coincide with the ones from unidirectional composite materials. We determined experimentally the coefficient of internal damping and eigen frequencies, for bars embedded at one end and free at the other, made from epoxy resin reinforced with wheat straw, targeted unidirectional, bidirectional and random. Keywords: composite materials, elasticity modulus, tensile strength, damping coefficient, wheat straw

Mesoporous silica was obtained by the acid attack of a serpentinite rock. This material was soaked with acrylonitrile (containing azobisisobutyronitrile as initiator) and the radical polymerization led to the obtaining of polymer inorganic-organic nanocomposites. The polymer nanocomposites were transformed in carbon-silica nanocomposites by the cyclization and graphitization of the carbon chain polymer. Heating the carbon-silica nanocomposite in nitrogen atmosphere allowed the synthesis of silicon nitride, a raw material for special ceramics. Keywords: radical polymerization, nanocomposite, silica, silicon nitride

In this paper the vascularization of typical porous polymer implant used for the dose provision of medicines is presented. Vessel growth was evaluated by simulation of spatial dispersions and nearest neighbor correlations of regional flows in a fractal tree model. Keywords: polymeric implant, vessel growth, fractal dimension

Bismaleimide monomers were used to prepare polymers in an attempt to achieve good properties. Bismaleimide BMI (1-3) were synthesized by reaction of maleic anhydride with diamines having hexafluoroisopropylidene units. Bismaleimides BMI (4-5) with ester units were synthesized by reaction between 3(4)-maleimidobenzoylchloride with diphenols.The monomers were characterized by infrared (IR), proton nuclear resonance ( 1H-NMR ) spectroscopy and elemental analysis. Thermal characterization of monomers was accomplished by differential scanning calorimetry (DSC), dynamic thermogravimetric analysis (ATG) and isothermal gravimetric analysis (IGA). In this paper , the synthesis and characterization of monomers with fluoro atoms in their structure is discussed. Keywords: bismaleimide, hexafluoroisopropylidene groups, synthesis, thermal properties

Well-defined block poly(e-caprolactone)-b-poly(dimethylsiloxane) (PCL-b-PDMS) copolymers with one or two PCL blocks were obtained via coordinated anionic polymerization of e-caprolactone by using hydroxy terminated PDMS oligomers both as initiators and comonomers. Molecular weights of these copolymers were varied over a wide range between 7200 and 30400 g/mol and the formation of copolymers with desired backbone composition were monitored by 1H NMR spectroscopy and SEC. DSC studies illustrated the formation of two phase morphologies, with PDMS and PCL transitions respectively and the influence of the copolymers structure on their thermal properties has been examined. Keywords: coordinated anionic ring-opening polymerization; block copolymer; crystallization

Polycarbosiloxane networks were obtained by the crosslinking reaction of bis(triethoxysilylethylene) cyclocarbosiloxanes. For this purpose 2,5-dimethyl-2,5-dihydro-3,4-diphenyl-1-oxa-2,5-disilacyclopentane and 2,7-dimethyl-2,7-dihydro-3,3,6,6-tetraphenyl-1-oxa-2,7-disilacycloheptane were modified with triethoxy-vinylsilyl groups via catalytic hydrosilylation. These monomers were characterized through spectral analysis by 1H-NMR, 13C-NMR and FT-IR. The crosslinking process of the cyclocarbosiloxane precursors was studied in various reaction conditions of temperatures and catalyst concentration. Using swelling measurements of the polymers in gelation state, the specific development of the polycyclocarbosiloxane network systems toward the final hyper-crosslinked state was investigated. Through this approach details concerning the influence of the precursor chemical structure over the characteristic evolution of the crosslinking process were revealed. Keywords: Polymer, Sol-gel, Polycarbosiloxane, Carbosiloxanes, Polycyclic