română MÜNIR TASDEMIR, UMUT YERLESEN
Abstract
In the present work, high density polyethylene based composites filled with glass spheres (hollow) and HDPE/glass spheres (filled with alumina silicate) particles were prepared. Fillers contents in the HDPE were 5, 10, 15, and 20 wt%. The mechanical, morphological and tribological properties of the polymer composites were investigated. Substantial improvements in the some mechanical properties were obtained by the addition of filler. For example, the results showed that the elasticity modulus of composites improved with increasing the glass spheres content. The addition of fillers to the HDPE changed significantly the friction coefficient and wear rate of the composites. HDPE filled with a high level content of fillers showed higher wear rate than pure HDPE under dry sliding. The structure and properties of the composites are characterized using a scanning electron microscopy (SEM).
Keywords
Tribological behavior, Wear, Mechanical properties, Friction, Polystyrene, High density polyethylene, Glass sphere
A.CANAKCI, T.VAROL, H. CUVALCI, F. ERDEMIR, S. OZKAYA
Abstract
In this study, novel CuSn10-B4C-graphite hybrid nanocomposite powders were synthesized by the solid-state powder processing technique of mechanical alloying. The effects of the addition of graphite particles, B4C distribution and milling time on the morphology, particle size and microstructure of CuSn10-graphite nanocomposite powders were investigated. It was found that the particle size of the nanocomposite powders was significantly lower than those of the CuSn10 alloy powders. Electron microscopy studies confirmed the formation of equiaxed graphite with a wide size distribution in the range of 100 to 200 nm.
Keywords
Mechanical alloying, Nanocomposite powders, Morphology, Electron microscopy
AURELIA CRISTINA NECHIFOR, ABBAS ABDUL KADHIM KLAIF RIKABI, DANIELA DUMITRA CLEJ, SZIDONIA-KATALIN TANCZOS, CORNELIU TRIŞCĂ-RUSU, CRISTINA ORBECI
Abstract
This study focuses on developing a new method to obtain Fe3O4-TiO2 nanoparticles and on their use through photocatalysis in environmental applications. The procedure for the preparation of Fe3O4-TiO2 nanoparticles occurs according to an in situ TiO2 synthesis and magnetite covered process. After preparation, the Fe3O4-TiO2 nanoparticles were exhaustively characterised by XRD (SAED), EDAX, TEM/HRTEM. The catalytic performances of the Fe3O4-TiO2 nanoparticles in environmental applications, at different concentrations, were evaluated in relation to the degradation of the ampicillin and penicillin G antibiotics, using a photocatalytic reactor with continuous recirculation. The reactor was equipped with an exterior magnetic field necessary to support the Fe3O4-TiO2 nanoparticles in the volume of the solution. Different concentrations of Fe3O4-TiO2 nanoparticles were used. The initial concentrations of the antibiotics were equivalent to 400 mgO2/L. Monitoring the concentration of the organic substrate took place by taking off samples from the reactor, at pre-established times, and analysing them using Chemical Oxygen Demand (COD). The values for the studied process variables were: pH of the solutions at 3 and H2O2 concentration of 1.5 per stoichiometric ratio. The effect of Fe3O4-TiO2 in environmental applications showed good activity in a UV light, able to degrade 97.5% ampicillin and 95.0% penicillin G in 2.0 hours of reaction time.
Keywords
Fe3O4-TiO2, Ampicillin, Penicillin G, Photocatalytic oxidation
MÜNIR TASDEMIR, SEZGIN ERSOY
Abstract
Fillers, in the form of particulates and fibers, are often added to polymeric materials to improve their stiffness and strength. Polymers and their composites are being increasingly employed in view of their good strengths and low densities. Besides, a wider choice of materials and ease of manufacturing make them ideal for engineering applications. High density polyethylene filled with particulate fillers is of great interest in both research and industry. It is well known that HDPE has good process ability allowing accepting different types of natural and synthetic fillers. As fillers, mica, kaolin, calcium carbonate and talc are the most often used to reduce both the production cost and to improve the properties of the thermoplastics, such as rigidity, strength, hardness, flexural modulus, dimensional stability, crystallinity, electrical and thermal conductivity. In the present work, high density polyethylene based composites filled with glass spheres, talc and calcite particles were prepared. Fillers contents in the HDPE were 5, 10, 15, and 20 wt%. HDPE composites filled with glass spheres, talc and calcium carbonate were prepared using extrusion compounding and injection molding. The effects of filler contents on the mechanical, morphological and thermal properties of the polymer composites were studied. The modulus of elasticity, yield and tensile strength, % elongation, Izod notched impact strength, Shore D hardness, MFI, HDT and Vicat softening point of the composites were determined. The structure and properties of the composites are characterized using a scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS).
Keywords
Mechanical properties, high density polyethylene, talc, glass spheres, calcite, polymer composites
The behaviour of the interface between carbon fibre reinforced polymer composite plates and concrete
NICOLAE ŢĂRANU, RUXANDRA COZMANCIUC, IOANA ENTUC, MIHAI BUDESCU, VLAD MUNTEANU, DORINA ISOPESCU
Abstract
The interface behaviour of fibre reinforced polymer carbon plates bonded to concrete represents a key issue in the efficiency of the strengthening solutions based on externally bonded composite plates.
An extensive research program was developed at the Faculty of Civil Engineering and Building Services from Iasi, to study the interfacial behaviour between carbon fibre reinforced polymeric composite (CFRP) plates and concrete. The study includes nine strengthened concrete elements which were tested under double shear pull testing set up. On the basis of the performed tests the recorded failure mode was the same for all tested specimens namely the interfacial failure. It essentially occurs in concrete close to the FRP plate-concrete interface.
The recorded data have been used to plot the load-slip curves and strains distributions along the composite bonded plates. Together, they served later on to calibrate the finite element method (FEM) based modelling accompanying the laboratory tests.
Keywords
externally bonded strips, carbon FRP plates, interface behaviour, finite element analysis
ANA-MARIA GHIŢĂ, HORIA ASANACHE
Abstract
The mathematical model of the semi-infinite massif was used to characterise building materials in case of thermal conduction in unidirectional non-stationary thermal regime. There were obtained informations about the evolution in time of the temperature inside the construction element. Thermal response was analyzed for the following building materials: cellular concrete block GBN35 masonry with thin joints, cellular concrete block Ytong A+ masonry with thin joints, solid brick masonry, reinforced concrete and cellular polystyrene. The results are useful for assessing the thermal insulation performance of building materials and improving the thermal comfort.
Keywords
thermal diffusivity, non-stationary thermal regime, thermal excitation of impulse-type
CRISTIAN OLIVIU BURADA, COSMIN MIHAI MIRIŢOIU, MARIUS MARINEL STĂNESCU, DUMITRU BOLCU
Abstract
In this paper, we have built some new composite sandwich platbands with polypropylene honeycomb core with the thickness of 10, 15 and 20 mm reinforced with two layers of glass fiber. We have chosen for the platbands the next width values: 45 and 60 mm. Starting from the dynamic response of these sandwich platbands with damping, that are in free vibration, we have established an experimental procedure to determine the damping factor per unit mass and unit length, loss factor, stiffness and the dynamic elasticity modulus.
Keywords
damping factor, loss factor, dynamic elasticity modulus, glass-fiber
NICOLAE DANIEL STOICA, MIRCEA BARNAURE
Abstract
For existing buildings masonry, numerical simulation of the seismic behaviour is difficult, involving complex nonlinear models. Testing large-scale models on shaking tables involves important costs and time. Still, the main purpose of testing or simulations is often to identify structural vulnerabilities probable failure modes so that the correct strengthening solution can be chosen. A simplified method for the assessment of the potential structural degradation pattern for simple masonry buildings is proposed. This method is based on energy dissipation and can be easily implemented by practicing engineers. Four case studies are performed using linear numerical models. The results are compared with observations on buildings tested on shaking tables.
Keywords
d. Masonry, d. Construction, c. Mechanical properties, b. Fracture, b. Modelling
RĂZVAN STATE, FLORICA PAPA, CORNEL MUNTEANU, IOAN BALINT, ALBERTO ION, ADRIAN VOLCEANOV
Abstract
Gold nanoparticles between 2 and 5 nanometers were synthesized using an easy obtaining method with good reproducibility using PVP as protective polymer and NaBH4 as reducing agent. The Au nanoparticles were characterized by TEM, XPS, XRD and UV-Vis. They are spherical with a very good dispersion making them suitable for a vast number of applications including catalytic and photocatalytic tests for nitrate and nitrite removal from water.
Keywords
gold nanoparticles, synthesis, characterization
SEZGIN ERSOY
Abstract
In the present work, the friction and wear property of high density polyethylene / Styrene - Butadiene Rubber polymer blends was studied. Styrene - Butadiene Rubber addition in the HDPE was 5, 10, 15, and 20 wt%. The result showed that the addition of fillers to the composite changed the friction coefficient and wear rate. All specimen wear loss increases with increasing load and sliding distance; meanwhile the friction (static and dynamic) coefficient increases. Wear rate of all HDPE composites are larger than that of pure HDPE. The results obtained in this study indicate that HDPE / Styrene - Butadiene Rubber polymer applied to the abrasion test indicate that road and load values to increase the effect of wear, but this effect by increasing the rate of Styrene - Butadiene Rubber additives lead to a reduction in wear is observed that value. In the friction test, the coefficients of friction are the rate of increase Styrene - Butadiene Rubber that the friction coefficient increases.
Keywords
Friction, wear, high density polyethylene, Styrene - Butadiene Rubber, polymer composites
MIHAELA VIOLETA GHICA, ANTON FICAI , ŞTEFANIA MARIN, MINODORA MARIN, ANA-MARIA ENE, JENEL MARIAN PĂTRAŞCU
Abstract
The aim of this study was to develop and characterize some new drug delivery systems based on collagen, bioactive (apatite – β-wollastonite) glass ceramics and doxycycline in order to be used in infected bone defects. The composites with different amount of glass ceramics were prepared as hydrogels by crosslinking and then freeze-dryed in order to obtain porous structures which mimic bone. The hydrogels were characterized by rheological behaviour and the the spongious forms by Fourier transform infrared spectroscopy (FT-IR) and water up-take. The in vitro behaviour was determined by collagenase degradation; the doxycycline release from spongious composite systems was investigated and the kinetic mechanism was determined. The results of this study indicated that the obtained composites are promising biomaterials for treatment and prevention of infected bone.
Keywords
collagen, bioactive glass ceramic, composite, drug delivery systems
-
Year
2015
-
Issue
45 (4)
-
Pages
307-314
MIHAELA (NIŢUICĂ) VÎLSAN, AURELIA MEGHEA, MARIA SONMEZ, DANA GURĂU, MIHAI GEORGESCU
Abstract
The aim of this work was to obtain polyolefin polymer composites reinforced with chemically modified layered clay: polyolefin/rubber/compatibilizer /nanoparticles. The technology of making these polymer composites is extrusion-granulation, in strict compliance with the order of introduction of ingredients. Embedding montmorillonite nanopowders in the polymer composite mixture helps to increase the thermal resistance of the nanocomposite. The obtained polymer composites were tested in terms of physical-mechanical (hardness, elasticity, tensile strength normal state and accelerated aging for 168h at 70°C), resistance to solvents (immersion in iso-octane) and structural properties (FT-IR), according to standards in force.
Keywords
composites, EPDM- terpolymer rubber, hardness, reinforcing, montmorillonite
NICOLAE DANIEL STOICA , MIRCEA BARNAURE
Abstract
Around the world there is a significant number of masonry buildings. Owing to the structural degradation during their existence, many of these structures require retrofitting interventions, especially those located in seismic areas. If masonry buildings have religious or cultural value, then the interventions should have a wider scope that aims to conserve the historical heritage. The Venice Charter of 1964 [1] includes two key principles guiding how this work should be carried out: the first principle is that structural interventions must be as less visible as possible, in order not to modify the aspect of the building; the second principle is that the action must be reversible, offering the possibility of dismantling should the interventions have poor efficiency. For this type of retrofitting works composite materials might offer several advantages. In particular, polymeric grids can ensure an enhanced resistance to the unreinforced masonry structures while not modifying their architectural aspect. The grids can be used for new buildings also, as they have some advantages with regard to the traditional solutions with steel reinforcement.
Keywords
d. Masonry, d. Construction, c. Mechanical properties, FRP, Polymeric grid, strength