فصلنامه مواد پیشرفته و پوشش های نوین
پیاپی 38 (پاییز 1400)

In this study, a hydrogel based on graft copolymer of itaconic acid (IA) onto chitosan (CS) was synthesized. For this purpose, the reaction was performed in nitrogen atmosphere and ammonium persulfate (APS) was used as an initiator and N,N-methylene bisacrylamide (MBA) as a crosslinking agent. In order to improve the water absorption, the effect of silver, silicon, and titanium oxide nanoparticles on hydrogel swelling was studied. Fourier transform infrared (FTIR) spectroscopy was used to confirm the structure and field emission scanning electron microscope (FESEM) used to study the morphology of the compounds. The presence of nanoparticles in the synthesized nanocomposites was confirmed by EDAX analysis. The results of water absorption showed that the synthesized hydrogel with 0.4 g MBA has the highest water absorption (19.7 g / g) and the presence of nanoparticles in the hydrogel structure increases the water absorption and SiO2 has the greatest effect so that the water absorption of nanocomposites containing silicon, titanium oxide and silver was obtained as 29.18, 26.92 and 23.47 g/g, respectively.

Polyurethane mastic coating (PU) according to IGS-M-TP-020-2 standard of Iran Gas Company is used as one of the insulation methods for pipes and fittings along with other insulation methods. In this study, hybrid nanocomposite coatings were prepared by mixing PU with 0.3 wt% by weight of multi-walled carbon nanotubes modified with different weight percentages of nanosilica in the thickness range of 1500-1000 μm. Characteristic tests were performed for coating application in gas transmission pipelines and the results were compared with pure PU sample. According to the analysis of transmission electron microscopy, the optimal amount of 1% by weight of nanosilica led to the proper dispersion of nanoparticles within the polymer structure. The high resistance of nanocomposite coating against moisture penetration and its hydrophobicity was justified by reducing the glide angle to 17o and increasing the sphericity of water droplets on the coating surface. Less than 100 mg of mass loss due to mechanical abrasion and a slight decrease in the adhesion of the coating on the steel surface (less than 15%) and the elongation (%) under standard tension in the range of 10-15% compared to pure PU coating, justifies its use as a new coating to increase the life of steel gas pipes. The results of this research regarding the mentioned tests indicate the observance of the technical standards of Iran Gas Company by the proposed coverage. Investigation of other technical requirements of the coating is essential in research futures.

Superhydrophobicity is the tendency of the surface to repel water droplets. Due to this unique property, superhydrophobic surfaces can be used in many areas such as waterproof surfaces, anti-corrosion surfaces, antifreeze surfaces, and anti-corrosion surfaces. In the present study, the superhydrophobic surface was generated using the spray pyrolysis method. The precursor to the coating process was stearic acid-modified alumina nanoparticles dispersed in alcohol. Increasing the deposition temperature, especially after 250 oC, reduced the roughness and hydrophobicity of the samples. Examination of deposition time showed that there is an optimal time for coating. In addition to experimental studies, the electronic properties and the mechanism of stearic acid adsorption on alumina surfaces were investigated with density functional theory (DFT) and molecular dynamics (MD) simulations. The superhydrophobic surface on the stainless steel substrate was obtained using a stearic acid-modified alumina suspension in 2-propanol alcohol at a temperature of 100 oC and 90 s deposition time with a water contact angle of about 160 °.

In this study, chitosan composite nanofibers containing tannic acid and zinc-based metal-organic framework (ZIF-8) were produced for application as a hemostatic wound dressing. First, metal-organic framework named zeolite imidazolate framework (ZIF-8) was synthesized and chitosan composite nanofibers containing tannic acid and ZIF-8 were fabricated through electrospinning. The effect of tannic acid and metal-organic framework on the morphology and hemostatic properties of chitosan nanofibers was studied. Scanning electron microscopy, X-ray diffraction and blood coagulation tests were utilized. The study of the morphology of nanofibrous wound dressings shows the fabrication of uniform and bead-free nanofibers with an average diameter of 120 to 150 nm. The addition of tannic acid, due to the formation of hydrogen bonds and increasing the viscosity of the polymer solution, increased the diameter of chitosan nanofibers. Prothrombin time (PT) and activated partial thromboplastin time (aPTT) tests, which check the performance of extrinsic and intrinsic pathway of blood coagulation, respectively, were used to evaluate the hemostatic activity of the fabricated wound dressings. The results show that the fabricated nanofibrous wound dressings significantly affect the extrinsic pathway of blood coagulation and factor VII, so that the blood coagulation time is reduced by 60% compared to the control sample. Due to the suitable structural and morphological properties of fabricated composite nanofibers, as well as their accelerated coagulation performance, they can be used as a suitable candidate in wound dressing applications.

Cellulose finds applications in the various fields as composite materials, textiles, drug delivery systems and protective products; in addition, cyclodextrins as a compound to improve these applications, can form inclusion complexes but cannot form direct covalent bonds to the textile materials, so it is important to achieve appropriate methods to anchoring cyclodextrins based on grafting polymeric compounds on the surface modification of the cellulose. In this study, binding of a reactive β-cyclodextrin to cellulose was investigated using chemical, physical and instrumental methods and the mechanism of grafting of reactive cyclodextrin onto the surface of cellulosic fabric was studied. Intended for grafting this compound on the cotton fabric, plasma technique was used to activate the surface to generate free radicals on cellulosic chains. According to the results, the yields of grafting the reactive derivative of β-cyclodextrin onto the surface of cellulosic fabrics increased by applying copolymers of this derivative and an intermediate monomer. In addition, the impact of the graft polymerization of these vinyl monomers on the performance of cotton fabric was evaluated and the results showed that although activation of the surface is attributed to cellulose degradation, the graft copolymerization monomers could be responsible for the compensating increase in its tensile strength and crease recovery in the suitable conditions. Furthermore, investigation the performance of the fabric in different conditions of surface activation and grafting of monomers, increases possibility of explaining the proposed mechanisms.

In this paper, the preparation of nanoparticles core-shell of gold-silica was carried out by coating of citrated gold particles using the Stöber method and products were investigated by XRD, uv-visible and TEM. In this method, first the nanoparticles were synthesized and then the silica shell was obtained. The results showed that gold nanoparticles have been successfully synthesized and results of transmission electron microscopy showed a particle size of about 20 nm. Preparation of coated gold particles with silica is successfully performed and the results showed a thickness of the shell in order of about 35 nm. The results of the uv-visible spectroscopy of gold nanoparticles and core-shell structure indicate a strong peak at 520 nm, characteristic plasmon peak of the gold particles. However, this peak is more intense for the core-shell structure, which is due to the scattering effect of silica shell having a resonant impact on the peak intensity.

In recent years, concerns about the presence of drug compounds as part of emerging pollutants have been growing. In this study, we tried to make aerogels with a high specific surface area and use them to remove the antibiotic oxytetracycline. Similarly, the resorcinol formaldehyde organic aerogel was synthesized using the sol-gel method and ambient drying. The synthesized RF aerogel was modified by the incorporation of 1 wt.% of amine-functionalized graphene oxide (GOA) and Meta-phenylenediamine during the synthesis process to prepare RF-GOA1 and RF-PmPDA1., and finally the performance of all three samples as adsorbents under different parameters such as pH solution, initial concentation of antiobiotic, adsorbent dose and different contact times adsorbent with antibiotics was investigated. FTIR, RAMAN, XRD, FESEM, BET, CHN, EDS tests were used to characterize the samples and then the performance efficiency of the samples oxytetracycline antibiotic remove was investigated using UV-Vis spectroscopic test. The results of BET test showed that the highest specific surface area is related to RF aerogel containing 1 wt.% amine-functionalized GO (RF-GOA1) with 266 m2/g. Also, according to the results, the adsorption capacity in aerogel samples was RF, RF-GOA and RF-PmPDA1 were 386.6, 257.6 and 277.8 mg / g, and the removal rate of oxytetracycline was 51.5 ,77.3 and 70.1% obtained, respectively.