ahmad mirshokraie - Academia.edu (original) (raw)

Papers by ahmad mirshokraie

تحقیقات علوم چوب و کاغذ ایران, 2010

In this study capability of acetylated poplar flour in manufacture of high density poly ethylene ... more In this study capability of acetylated poplar flour in manufacture of high density poly ethylene composite which expose to accelerated weathering, was investigated. The acetylation degrees at medium and zero (control) levels, use of anti- oxidant and duration of weathering were considered as variables and their effects on discoloration and photodegradation of WPC were investigated. To determine treatments influence on changes and color fade resulting from weathering, samples were tested after o, 250, 2000 hours of weathering. The results indicated that application of acetylated wood flour in WPC can reduce about 25% of weathering discoloration in short time and about 17% in long time. Also it shows that as exposed time of weathering increase Anti oxidant loss its effect. Although in short time it can reduce 12% of weathering color changes. FTIR results show that after 2000 h of weathering all peaks samples had same decrease which mean none of the treatments were useful. But Anti oxi...

Discoloration of wood due to biotic and abiotic factors or combination of both deteriorates the q... more Discoloration of wood due to biotic and abiotic factors or combination of both deteriorates the quality of wood, increases production costs and also decreases the quality of end-products. In this study, anatomical variations and topochemical distribution of lignin and extractives before and after drying and aging were investigated using the UMSP method. Chemical analysis was carried out using HPLC method. Results showed that increasing drying temperature up to 180 °C and increasing aging duration up to 6 months, increased extractives amount in vessel lumen and parenchyma cells and as well as lignin concentration in cell wall layers. A direct relationship between intensity of visual discoloration and the amount of UV absorption by extractives could be observed. It means that the higher the visual discoloration, the higher the absorption at 280 nm wavelength. HPLC analysis revealed that with increasing drying temperature and aging duration, higher and clearer discolorations in beach wood texture could be observed. Acetone and methanol extracts of discolored wood showed the presence of different low molecular compounds such as catechin and 2, 6 dimethoxy benzoquinon, which are transformed to high condensation compounds during kilndrying and aging.

Silicon, 2020

In this project, nano-MnO 2 @zeolite-Y (NMOZ) was successfully prepared via hydrothermal techniqu... more In this project, nano-MnO 2 @zeolite-Y (NMOZ) was successfully prepared via hydrothermal technique and its structure was confirmed using FT-IR, XRD, FE-SEM, EDX and BET analyses. MnO 2 nanoparticles stabilized on zeolite-NaY were used as nanocatalyst for efficient solventless preparation of 3,4-disubstituted isoxazole-5(4H)-one scaffolds via one-pot three-component reaction of ethyl acetoacetate, hydroxylamine hydrochloride, and aromatic aldehydes at 100°C. One of the advantages of this new method is the non-use of a metal oxidant such as KMnO 4 (greener method) and the stabilization of MnO 2 to the zeolite-Y surface via ion bonding. This causes the MnO 2 not be leached from the zeolite during the processes of nanocatalyst recycling in organic reactions. This simple approach also has promising features as like as safe, inexpensive and recyclable nanocatalyst, solvent-free reaction, short reaction times, high to excellent yields, and easy isolation of the products.

Floresta e Ambiente, 2019

The present study investigated the effect of heat treatment on the relative amount of cellulose i... more The present study investigated the effect of heat treatment on the relative amount of cellulose in untreated and nanosilver-impregnated poplar wood (Populus alba). The impacts on physical and mechanical properties were further studied. Specimens were heated at 145°C and 165°C in hot air medium. In order to enhance heat transfer to the inner parts of specimens, separate sets of specimens were first impregnated with nanosilver suspension in a pressure vessel. Differential scanning calorimetry (DSC) analyses showed that due to high thermal resistance of cellulose, the cellulose relative volume percent increased along with the increase in thermal temperature and the consequent degradation of other wood polymers (hemicellulose and lignin). High correlation was found between the cellulose relative volume percent versus different physical and mechanical properties. Impregnation with nanosilver increased thermal conductivity in the specimens resulting in an enhanced thermal degradation of hemicellulose and lignin, translated into an increased cellulose relative volume.

Green Chemistry Letters and Reviews, 2018

In this project, Ni(II) ion stabilized on zeolite-Y (NNZ) was developed as a high efficient nanop... more In this project, Ni(II) ion stabilized on zeolite-Y (NNZ) was developed as a high efficient nanoporous catalyst for the synthesis of 3-benzimidazolyl-1,3-thiazolidin-4-one derivatives via condensation of 2-aminobenzimidazole, aromatic aldehydes and thioglycolic acid in ethanol under ambient conditions. Compared with conventional protocols, this methodology has promising features such as the use of inexpensive, stable, recyclable and safe catalyst, shorter reaction times and higher yields, nontoxic solvent and easy isolation of the products.

Polymer Science, Series B, 2019

Hydrogels, nanogels, and nanocomposites have attracted much attention as drug delivery systems du... more Hydrogels, nanogels, and nanocomposites have attracted much attention as drug delivery systems during the past decades. In this work, a novel drug delivery system was synthesized by incorporation of nanogel into multi responsive hydrogel nanocomposite. At first, nanogel was prepared by copolymerization of N-isopropylacrylamide (NIPAM) and (2-dimethylamino)ethyl methacrylate (DMA). Then it was embedded it into pH, thermo, and magnetic responsive hydrogel nanocomposite including graft copolymerization of poly(2-dimethylamino)ethyl methacrylate (PDMA) onto salep (PDMA-g-salep) and Fe 3 O 4 nanoparticles (NPs). The synthesized samples were characterized by Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and atomic force micrographs (AFM). The sensitivity of the synthesized sample to temperature, pH, and magnetic field was studied using the swelling experiments. The drug release ability of the sample was also investigated at different pH, temperatures, and magnetic field. Finally, different kinetic models were used to discuss about the mechanism of drug release from the prepared sample. Our results represented the high efficiency of this kind of hydrogel nanocomposite for applications in cancer therapy.

Applied Organometallic Chemistry, 2019

Merrifield Resin was functionalized with metformine and applied as a solid support to immobilize ... more Merrifield Resin was functionalized with metformine and applied as a solid support to immobilize the CuCl 2. The Ps-Met/CuCl 2 was characterized by several techniques including Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), wavelength-dispersive X-ray spectroscopy (WDX) and inductively coupled plasma (ICP). The Ps-Met/CuCl 2 was used as an efficient recyclable solid nanocatalyst for N-arylation of indole and aniline through coupling reactions of Ullmann-type C-N. The advantages of this method are easy workup, improved yields, and simple recovery via filtration. Ultimately, the Ps-Met/ CuCl 2 antibacterial property was examined against two bacteria (Staphylococcus aureus (Staph. aureus) and Escherichia coli (E. coli)) and indicated its antibacterial performance against gram negative (E. coli) bacteria and gram positive (Staph. aureus).

Road Materials and Pavement Design, 2019

Different materials and compounds were used for improving mechanical and rheological properties o... more Different materials and compounds were used for improving mechanical and rheological properties of bitumen. Replacing the traditional bitumen by emulsion bitumen is increasing due to reduced environmental pollution. In recent years, emulsion bitumen modification has been considered to obtain higher efficiency bitumen with water-dispersible polymers. For this purpose, this study intends to investigate the modification of emulsion bitumen using waterdispersible anion polyurethane nanoclay nanocomposite. Since the polymer elasticity property plays an important role in bitumen modification and its properties, anionic polyurethane with different elastic properties was prepared by changing its structure, and its effects on modifying bitumen emulsion were investigated. Preliminary tests of bitumen properties and rheological behaviour analysis were performed on the prepared samples. The results of the tests showed that the penetration-modified bitumen decreased and softening point increased. As the structure of modifier changes, the rheological behaviour of bitumen is improved and changes from viscous to elastic one.

Journal of Inorganic and Organometallic Polymers and Materials, 2017

Anionic waterborne polyurethane as a new polymer dispersion was synthesized using relatively hydr... more Anionic waterborne polyurethane as a new polymer dispersion was synthesized using relatively hydrophilic polyols. Dispersing anionic polyurethane nanocomposites were prepared to investigate the effect of changing polyethylene glycol (PEG) molecular weight and percentage of clay nanoparticles added to the hydrophilicity of resin, polymer chain flexibility, particle sizes, particle dispersion, interactions of nanoclay and polymer, thermal stability, and changes in rheological behaviors. The composite was prepared from isophoren diisocyanate (IPDI), 2,2-bis (hydroxymethyl) propionic acid (DMPA), PEG with various molecular weights (Mn = 200, 400, 600, and 1000 g/mol), dibutyltin dilaurate (DBTDL), and triethylamine (TEA) using acetone method. Then, dispersing anionic polyurethane nanocomposites were obtained by dispersing different percentages (by weight) of clay nanoparticles in polymeric matrices. The nanocomposites were carefully dispersed in aqueous media in periods of time. In order to study the reactions progress and structural changes, different analytical techniques like FT-IR, 1H-NMR, particle size measurements, contact angles, thermal, and rheological stabilities, were used.

Iranian Polymer Journal, 2018

A novel thermo/pH/magnetic-triple-responsive nanogel was synthesized by grafting N-isopropylacryl... more A novel thermo/pH/magnetic-triple-responsive nanogel was synthesized by grafting N-isopropylacrylamide and acrylic acid onto sodium alginate to modify magnetic graphene oxide as a drug delivery system. The synthesized nanogel was characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), vibrating sample magnetometer (VSM), atomic force micrographs (AFM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The obtained nanogel displayed excellent reversible transmittance changes in response to pH, temperature, and magnetic field. The performance of the nanogels to load doxorubicin (DOX) drug and to sustain doxorubicin release was tested upon exposure to pH, temperature, and magnetic field variations. The mechanism of drug release was proposed in this paper by different kinetic models. In addition, the effects of nanogels and DOX-loaded nanogels on MCF-7 cells were examined and results were compared with free DOX drug. The in vitro results demonstrated that this triple-responsive nanogel can be an appropriate candidate for applications in cancer therapy.

Journal of Polymers and the Environment, 2017

Research on Chemical Intermediates, 2017

A series of new derivatives of 3-benzimidazolyl-2-aryl thiazolidinones, 4a-j are synthesized via ... more A series of new derivatives of 3-benzimidazolyl-2-aryl thiazolidinones, 4a-j are synthesized via a rapid, one-pot, three-component reaction by using La(NO 3) 3 Á6H 2 O as an efficient catalyst from the reaction of 2-aminobenzimidazole, aromatic aldehydes and thioglycolic acid in ethanol at room temperature. These new compounds were characterized by IR, 1 H, 13 C NMR and mass spectroscopies. An inexpensive and available catalyst, short reaction time, easy workup, good to excellent yields and nontoxic solvent are the advantages of this reaction.

Chinese Journal of Catalysis, 2017

Peptide nanofibers decorated with palladium nanoparticles catalyzed direct coupling of aryl halid... more Peptide nanofibers decorated with palladium nanoparticles catalyzed direct coupling of aryl halides with hydroxybenzotriazole to afford the corresponding biaryls in good to excellent yields. The coupling reactions proceeded under simple, green, and mild conditions. The peptide nanofibers were used as recyclable supports in the coupling reactions. This approach is the first to use hydroxybenzotriazole as a phenylating agent.

The Journal of Adhesion, 2016

ABSTRACT In this research, two different types of commercial tannins, namely a hydrolysable tanni... more ABSTRACT In this research, two different types of commercial tannins, namely a hydrolysable tannin (chestnut) and a condensed flavonoid tannin (mimosa), were used to prepare two types of soy-based (soy flour (SF) and soy protein isolate) adhesives for making plywood. Thermogravimetric properties (TGA) and its derivative as function of temperature (DTG) of different soy-based adhesive were measured in the range 40°C–300°C. Thermomechanical analysis (TMA) from 25°C to 250°C was done for the different resin formulations. Duplicate three-ply laboratory plywood panels were prepared by adding 300 g/m2 of the adhesives’ total resin solid content composed of SF or isolated soy protein (ISP), urea, chestnut, and mimosa tannin extracts with hexamine as hardener. Based on the results obtained, tannins can improve SF adhesion properties. The TMA showed that chestnut tannin extract appeared to react well with SF, while mimosa tannin extract appeared to react well with ISP. Matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry also showed that among other reactions, the soy protein amino acids reacted with the tannins. Furthermore, delamination and shear strength test results showed the good water resistance of plywood bonded with soy-based tannin modified adhesive.

Wood Material Science & Engineering, 2016

ABSTRACT Acid copper chromate fixation reactions on oak (Quercus castaneifolia C. A. Mey) sapwood... more ABSTRACT Acid copper chromate fixation reactions on oak (Quercus castaneifolia C. A. Mey) sapwood were characterized by at least two distinguished reaction periods which differ in their kinetic behavior, particularly reaction rate. In this research, chemical rate equation parameters were studied in detail as a function of chromium fixation time. Theoretically, the kinetic data were distinguished between the adsorption and reduction reactions and consequently, the rate parameters were determined for each stage distinctly. The obtained results showed that at the investigated thermal range (25–33°C), almost for every 3°C increase in temperature the reaction duration has decreased 20.4 min for the first reaction period and 78 min for the second reaction period. Besides that, in all sample replications, up to 58.3% of hydrogen ions function at the reduction reactions of the initial period, demonstrating that acidity (H+ ions) has a major effect on reaction rate constant. Accordingly, adsorption reactions of the hexavalent chromium at the starting point follow a pseudo-first-order kinetic reaction. Different to the adsorption reaction the CrVI reduction reaction is exothermic with a measured exothermal energy of 48.2 kJ/mol.

Bioresources, Jan 4, 2009

A fundamental study was carried out to explore the properties of canola stalks with regards to pu... more A fundamental study was carried out to explore the properties of canola stalks with regards to pulp and paper production. In this study the morphological properties, chemical composition, and soda pulping properties of canola stalks were investigated. The mean values of length, diameter, and cell wall thickness of canola stalks fibers were measured as 1.17 mm, 23.02 μm, and 5.26 μm, respectively. The morphological properties analysis indicated that despite the thicker cell wall, the morphological properties of canola stalks fibers were comparable to those of non-woods and hardwoods fibers. The holocelluloses, alphacellulose, lignin, and ash contents of canola stalks were determined to be 73.6, 42.0, 17.3, and 8.2 wt%, respectively. The hot water and dilute alkali extractives of canola stalks were determined as 18 and 46.1 wt%. In comparison to most other non-wood papermaking raw materials, soda pulping of canola stalks required higher chemical charge and cooking time. Soda pulping of canola stalks gave a low yield bleachable grade pulp. The strength properties of bleached canola stalks soda pulp appeared to be similar to those of common non-wood papermaking resources. The overall results showed that canola has a promising potential to be used in pulp and paper production.

2006 Pan Pacific Conference Proceedings Vol 2, Jun 1, 2006

Papers made from unbleached and bleached bagasse chemimechanical pulp were chemically modified by... more Papers made from unbleached and bleached bagasse chemimechanical pulp were chemically modified by acetylation. The effects of irradiation on unbleached and bleached also reduced papers of bagasse chemimechanical pulp before and after acetylation were investigated in this study. Chemimechanical pulp was prepared from bagasse and then bleached with hydrogen peroxide. Unbleached and hydrogen bleached pulps were reduced by Sodium borohydride in different procedures. Paper sheets were prepared from pulps and then acetylated using a technical grade of acetic anhydride. Accelerated photo-aging was run on the samples using fluorescent lamps to verify photo-stability of paper sheets before and after pretreatments. Brightness reversion (as Post-color number) and other optical properties of the paper sheets were measured. Efficient inhibition of photo-yellowing of papers made from bagasse CMP was achieved by acetylation. The acetylated unbleached CMP was noticeably photo-bleached during irradiation. Sodium borohydride reduction followed by acetylation had the same effect as acetylation alone at the same degree of reaction time and reductive treatment did not affect the yellowing rate to any great extent. The pre-reduced, acetylated unbleached papers were, however, not brightened during irradiation. Calculation done by Kubelka-Munk equation showed that reductive treatment had little effect in reducing the photo-yellowing of paper made from CMP pulp; a small stabilization effect was observed in the case of bleached CMP, while unbleached CMP was slightly more prone to discolor in the later phase of photo-reversion. The improved stability towards light may was closely related to the decrease in the phenolic hydroxyl content as a result of blocking by acetyl groups during treatment with acetic anhydride. The results support the hypothesis that phenolic hydroxyl has an important role in the process of photo-reversion of high-yield pulps. The results obtained in this study demonstrate that the acetylation of paper manufactured from peroxide bleached Bagasse CMP significantly retards light-induced discoloration. The inhibition of yellowing is connected with a decrease in the phenolic hydroxyl content of both unbleached and peroxide bleached papers.

European Journal of Wood and Wood Products, 2016

To diminish the formaldehyde emission, replacement of the formaldehyde by furfural in urea formal... more To diminish the formaldehyde emission, replacement of the formaldehyde by furfural in urea formaldehyde (UF) resin was investigated and its effect on formaldehyde emission and physical-mechanical properties of particleboard panels produced from poplar wood was examined. Resin type: Industrial UF, Laboratory UF, UF-Furfural (in 25 and 50 % replacement levels), and two press temperatures including 170 and 180°C were considered as variables. Results indicated that formaldehyde emission and modulus of rupture (MOR) of panels reduced thereby replacing the formaldehyde by furfural in UF resin. Internal bonding (IB) of panels made using 50 % replacement-modified resin was superior to others. Water absorption of panels decreased after 2-and 24-h immersion of samples with modified resins, as opposed to thickness swelling. The minimum thickness swelling was observed in panels made by Industrial UF resin. It is noteworthy that formaldehyde emission enhanced by increasing the temperature from 170 to 180°C, and also all physical-mechanical characteristics developed at 180°C temperature.

Bioresources

Structural and chemical changes were investigated in Hornbeam (Carpinus betulus) chips that had b... more Structural and chemical changes were investigated in Hornbeam (Carpinus betulus) chips that had been exposed to Phanerochaete chrysosporium BKM-1767 fungus. Samples subjected to fungal treatments for durations of 1, 2, and 4 weeks were investigated and compared with a control sample not subjected to fungal treatment. Results of scanning electron microscopy indicated that fungal hyphae were present on the surfaces of all chips exposed to the fungus. In the samples treated for a 2 or 4-week period, these hyphae additionally penetrated into vessels and lumens through ray cells, softening and destroying the cell walls. FT-IR spectra indicated that fungal treatment modified the chemical structure of the wood. Furthermore, there was a remarkable decrease in the amount of lignin in woods exposed to fungus. Lignin decreases after 1, 2, and 4 weeks of treatment were 2.83%, 11.4%, and 18.56%, respectively. Measurement of fiber dimensions indicated that cell wall thicknesses decreased after tr...