فصلنامه مواد پیشرفته و پوشش های نوین
پیاپی 23 (زمستان 1396)

Nowadays, Noise pollution control has great importance. Noise pollution causes harm to human’s body as well as distressing calmness. One way to control noise is the use of sound absorbing materials (especially polymer foams). In recent years, composite polymers especially interpenetrating polymer networks have received much attention because of the improved properties of polymers. Polymer composites with interpenetrated polymer network structure (IPN) are widely used as sound and vibration damping agents due to their high viscoelastic properties, within the glass transition temperature range. In this study, IPNs foams of polyurethane (PU) and poly(methyl methacrylate) (PMMA) were prepared by in situ polymerization using different ratios of PU/ PMMA (85:15, 75:25 and 65:35).
IPN components including polyurethane and polyethyl methacrylate were synthesized separately to compare thermal properties, attenuation, mechanical and sound absorption coefficient of polymer. The chemical structure of the compounds was investigated by FT-IR spectroscopy and mechanical properties were studied using Tensile testing machine.
Damping and thermal properties of the samples were performed using dynamic mechanical analysis (DMA) and thermo gravimetric (TGA) respectively. Measuring the absorption coefficient was performed using the Impedance Tube (SW60, BSWA) in the frequency range from 63 to 6300 Hz, according to ISO10534-2. As indicators of effective damping capability, viscoelastic parameters including loss factor (tan δ), glass transition temperature (Tg) and effective damping interval (tan δ > 0.3) were also determined.
The formation of a semi-compatible morphology was indicated by the broad tan δ curve and two distinct transition peaks observed in the DMA curves of IPNs. The results revealed that formation of IPNs foams compound due to transform of glass transition temperature to higher temperatures and temperature of damping was increased. Therefore, in the result of the PU / PMMA IPNs damping properties were improved. Results show that because of the formation of IPN, the sound absorbing capacity of prepared samples increased at a certain frequency, and the resonance frequency shifted to lower frequencies by increasing the PMMA content in IPN foams.
Therefore,it is possible to realize a purposeful selection of sound-damping materials for solving specific technological problems by varying the composition of the material.

This study demonstrates a solution-phase polyvinylpyrrolidone (PVP)-assisted approach to prepare shape-controlled plasmonic Ag nanostructures in ethylene glycol (EG) solution via heterogeneous nucleation (in the presence of FeCl3). Combining with experimental study, molecular dynamics (MD) simulation is also used to understand the underlying principles governing nanowire growth through the analysis of the interaction energies between crystal surfaces and capping agent as well as atom density profile. The simulation results indicate that the PVP concentration, as a capping ligand and shape-directing agent, plays a key role in the anisotropic confinements during growth process of nanowires because the interaction energy between PVP molecules and silver crystals (through Ag : O coordination) on (100) and (110) planes is stronger, which leads to oriented attachment of crystals and the anisotropic growth on the (111) planes. Furthermore, the plasmonic properties of the as-synthesized nanowires are confirmed by UV-Visible spectra displaying a dual-peak absorption ascribed to the transverse dipole resonance (longer wavelength, λ=420 nm) and the transverse quadrupole resonance (shorter wavelength, λ=380 nm).

In this study, sodium montmorillonite clay (Na+-MMT) nanoparticles were surface modified by azole corrosion inhibitors such as 2-mercaptobenzothiazole (MBT) and 2-mercaptobenzimidazole (MBI) through ionic exchange reaction and used as anti-corrosion nanopigments inside epoxy resin. Small angle x-ray scattering (SAXS) and transmission electron microscope (TEM) tests were used to evaluate the distribution of hybrid nanopigments within the matrix of coating and the structural morphology of the compounds was investigated by scanning electron microscopy (SEM) test. Electrochemical impedance spectroscopy (EIS) and salt spray were also implemented to study the corrosion behavior of nano coatings in the corrosive environment of 3.5% sodium chloride solution. Additionally, contact angle measurement was used to evaluate the levels of hydrophilicity and hydrophobicity of steel surfaces coated with and without clay compounds optimized with azole compounds. The results indicated that epoxy coating containing 3 wt. % of MMT+MBT nanopigment, compared to epoxy coating containing 3 wt. % MMT+MBI and pure epoxy coating had higher anti-corrosion performance after 60 days of immersion in the above-mentioned corrosive environment and presence of this nanopigment led to an increase of the level of hydrophobicity in the related surface.

In this study, water based acrylic copolymers were used as base coatings and the effect of adding silica nanoparticles was investigated in the hydrophobic properties of coating. In addition, the presence of titanium dioxide nano particles creates the self-cleansing properties in the coating. In this study, calcium carbonate stones are used as the mineral substrate from the historical site of Persepolis in Fars province. The morphology and cross-sectional of coatings were studied by scanning electron microscopy (SEM). Characterization of these materials was carried out with the various analyzes, including the FTIR, X-Ray Analysis (XRD), Atomic Force Electron Microscopy (AFM), and Contact Angle measurements. The results indicated that the addition of nano silica to acrylic copolymers improves hydrophobic properties. Furthermore, nano silica improves surface roughness and improves resistance to artificial aging conditions (accelerated weathering test). In addition, the photocatalytic effect of samples with titanium dioxide particles was investigated at different interval times.

Carbon and low-alloy steels are the major construction materials extensively used in water distribution, petroleum, power production, as well as chemical and electrochemical industries. The use of organic molecules as corrosion inhibitors is one of the most popular, efficient, and practical methods applied extensively to protect metals against corrosion damage. In present study, N-phenyl hydrazinocarbonyl acrylic acid (N-PHAA), N-2,4-Dinitro phenyl hydrazinocarbonyl acrylic acid were synthesized from reaction of Phenyl hydrazine with maleic anhydride (MA) in DMF and reaction of 2,4-Dinitro phenyl hydrazine with maleic anhydride (MA) in acetone at room temperature. All compounds were characterized by FT-IR. Yield and temperature of thermal decomposition of products of (NPHAA) and (NDNPHAA) were obtained as 73%, 214-216 ̊C and 89%, 131-133 ̊C, respectively. Then, synthesized compounds used as the corrosion inhibitor. For next stage, 10-150 ppm of synthesized corrosion inhibitor were added to base oil and used for covering on the surfaces of low carbon steel samples as temporary protective coatings, the covered steel samples located in chamber with 100% relative humidity and at 38 ̊C their protection determined according to ASTM D-2247. Synthesized inhibitor compounds showed the best resistance against corrosion in 75 ppm and (NDNPHAA) showed the best results.

Since the treatment of spinal cord injury is not easily curable due to the complexity of the central nervous system, the ways of regeneration and repair of the neural tissue have been very much considered, in the world. In this study, two types of conductive (PCL / PANI- PLGA) and non-conductive (PLGA - PLGA) scaffolds with three - dimensional core–shell structure were designed and produced by combined electrospinning method. This system has a water vortex system and a two - nozzle system, and is capable of producing 3D cylindrical scaffolds with nanorough shell and aligned core (parallel microstrands including aligned nanofibers). Based on in vitro and in vivo tests, the highest proliferation of nerve cells was observed on the 3D scaffold (PCL / PANI-
PLGA) with conductive core. Also in animal studies, the results of the motor test indicated a significant improvement in the transplanted samples compared to the control samples.

Recent studies to solve environmental pollution problems are directed to self decontaminating films. The most important and applicable mechanism is useing photocatalytical procedure. In this study, TiO2/Ag dye composite was synthesized by liquid impregnation method from two prime structures of titanium dioxide (anatase and rutile), with 2% of silver nitrate. The composite was characterized by SEM-EDX and UV-Vis. To determine the accuracy of the composite potential to decompose the pollutant in visible region, a halogen lamp of 100 W was used to degrade 1 mg/L of Rh.B. The result was 60% degredation of Rh.B within 240 min. Dispersion of nano-composite TiO2/Ag in acrylic semi-gloss paint business coatings was conducted by SEM. The results indicated that 100 mg/L Rh.B on the surface of dye containing TiO2/Ag composite was 40% degraded after 6 h illumination under 100 W halogen lamp.