حامد یونسی کردخیلی

Given the low precipitation and frequent occurrence of droughts in Iran, it is crucial to devise basic plans and identify new methods to mitigate the effects of drought on fodder production resources. Saltbush (Atriplex canescens (Pursh) Nutt.), extensively cultivated in Iran for desert restoration, is one such plant.

To investigate the effects of nano-zinc oxide and its efficacy in creating resistance to drought stress on the growth and physiological variables of one-year-old saltbush seedlings, an experiment was conducted in a completely randomized design with four replications. The experimental treatments included seed nano priming using nano-zinc oxide at concentrations of 0, 30, 100, 300, and 1000 mg/liter, and drought stress at four levels of field capacity: 20%, 40%, 60%, and 80%.

The results showed that as soil moisture decreased, the growth characteristics of seedlings, including the number of branches, leaves, collar diameter growth, fresh and dry weight of aerial parts, and fresh and dry weight of roots, decreased. The highest values of these characteristics were observed in the 80% treatment and the lowest in the 20% field capacity. With increasing drought stress, leaf physiological characteristics such as chlorophyll a, total chlorophyll, carotenoid, and proline increased. The investigation into the effect of nano-zinc oxide on the growth characteristics and physiology of saltbush seedlings revealed that this nanoparticle significantly affected only chlorophyll a, total chlorophyll, and proline. The highest amount was observed in the control seedlings, and the lowest was in the nano-zinc oxide treatment with a concentration of 1000 mg/liter.

In general, due to the very insignificant effects of zinc oxide nanoparticles observed in this research, their use to increase the resistance of saltbush to drought stress is not recommended.Keywords: Environmental stress, field capacity, proline, seedling growth, total chlorophyll.

The aim of this study was to compare nanolignin and ionic liquid (IL)-treated lignin as new compatibilizers in Wood-Plastic Composites (WPC). For this purpose, lignin was extracted from black liquor and modified with [Emim][OAc]. Then, the modified lignin was used as a compatibilizer in the WPC.  Nanolignin was prepared by an acidic method, and its performance was compared to that of ionic-liquid-treated lignin as a compatibilizer in the composites. Nanolignin and ionic liquid-modified lignin at the same levels (1, 3, and 5 wt%) were added to the wood flour and polypropylene mixture, and WPCs were manufactured using the hot press method. In the next step, all physical and mechanical properties of the prepared panels were analyzed using standard methods. FTIR analysis indicated that modification of lignin by an ionic liquid can change some chemical bonds and even produce new bonds.  However, the chemical structures of the virgin lignin and nanolignin were similar. The physical and mechanical properties of the prepared composites indicated that the addition of both forms of lignin significantly increased the dimensional stability, bending properties (flexural modulus and flexural strength), and impact strength of the composites. Based on the findings of this research, IL-treated lignin exhibited better physical and mechanical results as a coupling agent in wood plastic composites compared to nanolignin; thus, the composites with 5 wt% have the highest mechanical strength and dimensional stability among all lignin-containing samples.

Nowadays, finding a catalyst with high quality and eco-friendly thermoset resins is very valuable. This study aimed to investigate the effect of maleated lignin-based polyacid (MA-PL) as a catalyst in urea-lignin-glyoxal (ULG) resin. For this reason, a phenolate reaction was done to increase the hydroxyl groups of lignin. Then the modified lignin was reacted with maleic anhydride to obtain polyacid based on maleated lignin. In the next step, different content of MA-PL catalyst (0, 1, 2, and 3 wt%) was added to ULG resin and prepared resins were used in particleboard panels production. Different properties of synthesized resins and panels were measured according to standard methods and were compared with those using ammonium chloride as the control sample. In addition, the thermal behavior of resin before and after adding catalyst was analyzed with Differential Scanning Calorimetry (DSC). Generally, the results of this research indicated that polyacids based lignin could be used as a suitable catalyst for ULG resin. Physical and mechanical test analysis indicated that the addition of catalyst from zero to 3 wt% continuously decrease pH and gelation time. DSC analysis showed that adding extra MA-PL reduces the curing temperature of resin compared with ammonium chloride. Based on the obtained results from manufactured panels, mechanical strength (MOE, MOR, and IB strength) and dimensional stability of the panels was improved by adding 3 wt% MA-PL.

In this study a nontoxic aldehyde with high boiling point entitled glyoxal was used for reaction with urea and Kraft lignin to prepare green adhesive entitled urea- lignin- glyoxal (LUG). The prepared LUG resin had used in particleboard manufacturing. Then the influence of nanoclay addition on various properties of particleboard made from LUG resin was investigated. For this reason, the kraft lignin (10 wt%) was used instead of second urea in urea- glyoxal resin synthesis. After LUG resin synthesis in acidic condition and measuring physicochemical properties of the prepared resins, the prepared LUG resin was mixed with the 0.5, 1 and 1.5% nanoclay by mechanically stirring for 5 min at room temperature. Then the prepared resin was used in particleboard manufacturing. The physical properties of the prepared resins such as viscosity, gelation time, solid content and density as well as physical (water absorption) and mechanical (internal bond strength and flexural properties) properties of manufactured panels were measured according to standard methods. Also X-ray Diffractometry (XRD) was used to investigate the distribution of nanoclay on LUG resin. The physical test results indicated that gelation time of the LUG resin is slower than that of UF resin. Addition of nanocaly from 0.5 to 1.5% accelerates the gelation time of the prepared resins whereas the fastest gelation time related to the LUG resin containing 1.5% nanocaly. Also XRD analysis indicated that nanoclay could good separate when was mixed with LUG resin. Based on obtained result, the addition of nanoclay decreased the water absorption content of the manufactured panels, significantly. The internal bond strength and flexural strength of the panels was increased by addition the amount of nanoclay. Finally it must be noted that the addition of nanoclay had no significant effect on flexural modulus of the manufactured panels.

In this research, the effect of nanoclay on physiochemical, thermal and structural properties of urea formaldehyde resin (UF) was investigated. The prepared GLUF resin was mixed mechanically with the 0.5, 1 and 1.5% nanoclay for 5 min at room temperature. The physicochemical properties of the prepared resins were measured according to standard methods. Also, the thermal and structural changes in UF resin containing nanoclay were measured by Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectrometry (FTIR) and X-ray Diffractometry (XRD). The physicochemical test results indicated that by addition of nanoclay the viscosity, solid content and density values were increased while the free formaldehyde and gelataion time of resin were decreased. FTIR analysis indicated that the addition of nanoclay decreased the methylene linkages in UF resin. Moreover, the new peak was appeared at 850 and 1140 cm-1 bands in nanoclay filled UF resin dealing that a chemical interaction between nanoclay and UF resin was accrued. According to DSC analysis nanoclay accelerates the curing temperature of resin while the onest and temperature peaks dramatically decreased. XRD analysis showed that nanoclay completely exfoliated in UF resin.

In this study, some of the physical and mechanical properties of polypropylene fiber/ wood fiber/ cement composites were investigated. For this aim, three levels of polypropylene fiber, namely 2 wt.%, 3 wt.% and 4 wt.% were mixed with 15 wt.% of wood fiber mixed with cement in a rotary type mixer. The samples were formed by cold press method. Then water absorption, thickness swelling, flexural modulus, flexural strength, and impact strength of the manufactured composites were evaluated according to ASTM standard methods. The results showed that polypropylene fiber exhibited a positive effect on physical and mechanical properties of the wood- cement composites. The physical test results indicated that the hybrid composites containing 4% PP fiber/11% wood fiber exhibited the lowest water absorption and thickness swelling values. The mechanical test results also indicated that greater flexural strength and impact strength can be achieved by addition of 4% polypropylene fiber to wood- cement composites. Also the three point bending test results showed that addition of PP fiber from 2 to 4% decreased flexural modulus of the wood- cement composites, continuously.

One of the solutions to increase the applications of lignin molecules is increasing reactive functional groups by chemical modification. Adding reactive functional groups into the lignin structures is one the best proposed methods. The aim of this study was to investigate change in structure as well as glass transition temperature (Tg) of Soda and Kraft lignins after hydroxymethylation them with non-volatile aldehyde entitle Glyoxal. Kraft and Soda black liquors were prepared from Choka and Pars Co, respectively. Lignins were extracted from black liquors by acidic method. Then changes in structure and thermal properties of the glyoxalated lignins were measured with Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC) compared to pure lignins, respectively. The results indicated that glyoxalation increase reactive functional groups in lignins. Also FTIR result indicated that glyoxalation made some changes in lignin structure. DSC analysis showed that Tg of Soda and Kraft lignins reduced by glyoxalation. Finally DSC and FTIR analysis indicated that Soda lignin exhibited better potential for glyoxalation and have lower Tg compared to Kraft lignin.

The properties of catalyzed organosolv pulp obtained from maple juvenile wood were studied. The physical properties of fiber (e. g. length، width، and cell membrane thickness) and chemical composition of maple juvenile wood (e. g. average cellulose، lignin، extractives، and ash content) were determined. The variables were cooking temperature (190 and 200 ºC) and time (40، 60، and 80 minutes). Chemical charge (280 ml methanol، 70 ml water، and 0. 025 mols of Calcium Chloride and Magnesium Nitrate) was kept constant. Pulp screen yields (54. 9 to 60. 91%) and Kappa No. (15. 5 to 18. 4) were measured. Pulp freeness was reduced to 350 ml CSF in PFI mill، and ten 60 g/m2 handsheets were made from the selected pulps. The strength properties of catalyzed organosolv handsheets including tear length (3. 83 to 4. 25 km)، tear index (10. 22 to 12. 81 mN. m2/g)، and burst index (1. 74 to 2. 15 kPa. m2/g) were compared with those of the conventional Kraft handsheets of maple juvenile wood. The least allowed values of the mentioned properties in the Indian (IS) and Japanese international standards (JIS) reveal that while the tear length value is slightly below that of the standards، the values of tear and burst indices are well beyond the given standards، and the environmentally-friendly catalyzed organosolv pulping process (higher yield and lower Kappa No. compared to Kraft) can be recommended to produce paper pulp from maple juvenile wood.

In order to eliminate the harm of formaldehyde from panels bonded with UF resin to environment and human health at the source, the low volatile and nontoxic aldehyde of glyoxyal (G) was chosen to react with urea (U) to prepare the wood adhesive of urea-glyoxal (UG) resin a substitute for urea-formaldehyde (UF) resin. The urea-glyoxal (UG) resin was synthesized under weak acid conditions, and its different properties were measured. Also, the effect of nanoclay on physico-chemical, thermal and mechanical properties of UG resin was investigated. For this purpose, the prepared UG resin was mixed with 1, 2 and 3 wt% nanoclay by mechanically stirring for 5 min at room temperature. The physico-chemical properties (such as SPG, viscosity, solid content and gelation time) and dry shear strength of the prepared resin were measured according to standard methods. Also, the effect of nanoclay on curing temperature of UG resin was analyzed by Differential Scanning Calorimetry (DSC) device. The physico-chemical test results indicated that addition of nanoclay increased SPG, viscosity and solid content of UG resin and decreased gelation time in the prepared resin. Dry shear strength test results showed that increasing nanoclay content from 1 to 3 wt% increased shear strength of UG resin; as the panels containing 3% nanoclay exhibited the highest shear strength value and wood failure percentage. Based on DSC test results, hardening rate as well as enthalpy value of the prepared UG resin was decreased by addition of nanoclay.

The aim of this research is investigation on influence of single wall carbon nanotubes (SWCNTs) on the physical and mechanical properties of wood fiber- LDPE composites. SWCNTs with 1, 2 and 3 wt% were dispersed in acetone and then in absent and present MAPE (0 and 3% wt) were mixed with wood fiber and HDPE by Haake internal mixer and then the wood plastic composites were manufactured by hot press method. The results show that SWCNTs and MAPE improve physical and mechanical properties of the composites. In absent and present MAPE, the composites with 3% SWCNTs exhibited the lowest water absorption and thickness swelling content and the highest flexural modulus and strength, respectively. SEM micrograph showed that, with adding compatibilizer dispersion of fibers and carbon nanotube are improved. The composites with 3% MAPE and 2% SWCNTs exhibited the highest impact strength. Based on SEM micrograph, with increasing carbon nanoyube up to 3%, these nanoparticles are agglomerated in the matrix and provide points of stress concentrations and crack propagation.

In this study, the effect of Kraft lignin was investigated on the short term water absorption as well as mechanical properties in wood flour-polypropylene composites. Kraft lignin was extracted from black liquor by acidic method and mixed with the wood flour with ratio of 0, 2, 5 and 10 percent (based on wood flour dry weight) by solvent mixing method. The composites were manufactured by hot press method after mixing of the wood flour, the lignin, the polypropylene as well as the MAPP (0 and 2%) in internal mixer. The physical and mechanical properties of prepared samples were determined according to standard test methods. The results showed that the lignin improved physical and mechanical properties of the composites and it can be used as co-compatibilizer of MAPP in the wood plastic composites. The bending test results showed that in absence of MAPP, the composites with 10% lignin exhibited the highest flexural modulus and flexural strength. However at presence of MAPP, the composites with 5% lignin exhibited the highest flexural modulus and flexural strength. In absence and presence of MAPP, the composites with 10% lignin exhibited the lowest water absorption and the highest impact strength.

The purpose of this study was to investigate effects of different loading levels and addition of urea formaldehyde and polyethylene on the creep behavior of composites made from wastes of OCC recycling mills. The composites manufactured by hot press method and three-point bending test performed before creep test. In general, the results showed positive effects of additive materials such as urea formaldehyde and polyethylene on the creep behavior of the composites. While adding UF and PE decreased primary and final creep as well as return deformation percentage of the composites. Also the obtained results indicated that remaining creep had higher sensitivity to loading levels compared to primary and final creep. Also the increase of the load levels from 20% to 30% led to an increase in creep content of the composites.

In this research, water and steam absorption behavior and also effect of maleic anhydride polypropylene (MAPP) on these behaviors in wood fiber-polypropylene composite were compared. For this purpose, the composites were manufactured from 60% fibers and 40% polypropylene in presence and absence of MA. The oven dried samples with dimensions of 2.5×2.5×1 cm were immersed in distilled water and exposed to water steam. Long-term water and steam absorption and thickness swelling of the composites were studied. The results showed that the composites exposed to water steam exhibited higher water absorption and thickness swelling than those immersed in water. The addition of 2% MA decreased steam and water absorption and thickness swelling in studied composites.

Effect of Kraft lignin as a compatibilizer on the short-term water absorption (2 and 24 hours) and mechanical properties of wood flour-polypropylene composites was studied. The black liquor of Chooka pulp and paper mill was acidified and Kraft lignin was extracted by precipitation. The extracted lignin at three levels of 2, 5 and 10 percent was mixed with wood flour by physical mixing method. All materials used were oven-dried. Wood flour, lignin and PP with or without MAPP were used to produce composites by flat hot press method. The results of this study indicated that generally lignin improved physical (short term water absorption) and mechanical properties (flexural modulus, flexural strength and impact strength). The bending test result showed that without MAPP, the composites with 2 and 10 percent lignin exhibited higher flexural modulus and strength, respectively. But at the presence of compatibilizer, the composites with 5 percent lignin exhibited the highest flexural modulus and strength. The composite with 2 percent of lignin exhibited higher flexural modulus and short-term water absorption rather than the composites with 2% MAPP. This result indicated positive effect of lignin in the composites. Also the composites with 10 percent lignin exhibited the highest impact strength and short-term water absorption. But there were no significant difference between the impact strength of composites with 5 and 10 percent lignin.

In this study، the effect of two lignin mixing methods on physical and mechanical properties of wood flour- polypropylene composites was investigated. Kraft lignin was extracted from black liquor by acidic method and was mixed with wood flour by physical and chemical methods with ratios of 2، 5 and 10 percent (based on wood flour dry weight). The composites were produced by hot press method after mixing of wood flour، lignin and polypropylene at presence or without MAPP. The physical and mechanical properties of prepared samples were measured according to standard methods. In general، the results showed that adding lignin to composites decreased water absorption in both methods. Also increasing lignin from 2 to 10 percent increased impact strength of composites with or without MAPP. Flexural strength of the composites differed depending on mixing method. Increasing of lignin decreased flexural strength of the composites without MAPP in the physical mixing method where as in chemical mixing method it was increased. It is to be noted that the composites with 5 percent lignin، made with physical mixing method and with MAPP exhibited higher flexural strength than other composites.