مجله تحقیقات علوم چوب و کاغذ ایران
سال سی و دوم شماره 3 (پیاپی 60، پاییز 1396)

This study and it aim was accomplished on the effect of TCF bleaching on optical and mechanical properties of CMP pulp. For this purpose, some unbleached CMP pulps were randomly selected from Mazandaran Wood and Paper Industries (MWPI). Then these pulps were bleached with two and three OP, OPY, PY and O(Eo)P bleaching stages by using oxygen(O), alkali extraction with hydrogen peroxide(Eo), sodium dithionite(Y) . The hand sheets with 70 gr/m2 were prepared from above-mentioned of pulps, and then the optical and mechanical properties were measured and compared according by using TAPPI Standard test methods. The results showed that brightness, greenness, folds breaking length, tensile and tear strength were increased and opacity and a* factor were decreased. In general, role of three O(Eo)P stages and two OP and PY bleaching stages were better than P stage and unbleached CMP pulp mill in improve of brightness and its paper strength, too.

In present study, the adhesion strength of polyurethane and alkyd coatings on the poplar wood (Populus nigra) was improved by nano-silane coating using sol-gel method for outdoor application. For this purpose, the boards with dimensions of 15 × 10 × 2 mm were prepared according to EN 927-5. The surfaces of wood specimens were modified with Tetraethoxysilane (T) sol-gel material and then, solvent-borne alkyd (AS) and solvent-borne polyurethane (PS) coatings were applied. The coated samples were placed outdoor on a platform with a slope close to Karaj latitude (36̊) for 8 months according to ISO 877 standard. In order to characterize the quality of the coatings, colorimetric, tensile adhesion (Pull off), scratch adhesion (Cross cut) and ATR-FTIR tests were performed before and after weathering. The ATR-FTIR analysis demonstrated that the wood surface was covered with silicon oxides (SiO2) attached to hydrocarbon chains. As a result of surface wood modification by sol-gel, the color and adhesion strength of polyurethane and alkyd coatings were less affected by weathering. The highest tensile and scratch adhesions were found for the combined sol-gel and polyurethane coatings.

In this research was to use the effects micro cellulose, and Multi walled Carbon Nanotube on the mechanical properties of wood plastics composites. This article presents the application of Multi walled Carbon Nanotube in order to evaluate and compare their suitability as reinforcement for thermoplastics. The effects of loading micro cellulose and Multi walled Carbon Nanotube content on the mechanical properties were also studied.
The results showed that mechanical properties of the composites made with 50 micron cellulose and 1.5 and 2.5 % of Multi walled Carbon Nanotube were significantly superior to those of the lower length (20 micron) and control samples. Addition of Multi walled Carbon Nanotube could enhance the mechanical properties of the blends, due to the improvement of interface bond between the filler and matrix of wood plastics composites. The significant improvements in mechanical properties of the blends composites made with Multi walled Carbon Nanotube and micro cellulose were further supported by SEM and TEM micrographs.

Paper works are more attacked by biological agents such as fungi, bacteria and insects due to its organic nature. In ýarchives, most of the biological destruction of paper is related to fungi. The importance of paper works ýconservation has led to applying different methods to fungus removal. The chemical disinfection is of of the most ýcommon disinfection methods. In this research, the application of Thiophanate methyl in paper destructive fungi ýhas been studied. Laboratory studies to evaluate the effects of Thiophanate methyl on paper and fungus include ýaccelerated ageing, the evaluation of effectiveness of antifungal Thiophanate methyl on fungi such as ýAspergillusniger, Aspergillusflavus and Penicilliurnsp and determination of antifungal stability after accelerated ýageing. Examination shows that Thiophanate methyl has successfully prevented spread of fungus in all density of ýþ10þý, ýþ50þý, ýþ100,200þý and ýþ500þý ppm. Aspergillus flavus fungus had a slight growth at ýþ10þý ppm, but no growth were ýobserved in other density. Aspergillusniger fungus had no growth capacity in density more than ýþ100þý ppm. ýAccording to the results, treated papers are still able to control fungus growth after being in accelerated ageing ýcondition. In general, the results obtained by fungus growth halo and non-growth halo indicate that all fungi are ýcontrollable in density of ýþ200þý ppm.ý

The aim of this research is the possibility of using black liqour and nano Graphene oxide (GO) for making three-layer particle board. In this study, the amount of black liqour was as 0, 10, 20 and 30 percent and Graphene oxide was 0, 0.25 and 0.5 percent (based on oven dried weight of UF). Wood particles was pressed with using a laboratory hydraulic press. Mechanical and physical properties (modulus of rupture, modulus of elasticity, internal bonding, water absorption and thickness swelling after 2 and 24h soaking in water) of the produced boards were measured according to EN standards. The effect of each of the variables was studied on the properties and analyzed at 95 percent with using SPSS software and variance analysis factorial design. The results showed that increasing black liqour resulted in decreasing the modulus of rupture, modulus of elasticity and internal bonding. The results also indicated that water absorption and thickness swelling after 2 and 24h soaking in water increased with increased black liqour and Graphene oxide percent. The results show that increasing of nano ghraphen resulted in increasing modulus of rupture, modulus of elasticity and internal bonding.

In this research, two types of lignin, i.e. one extracted from industrial waste water of the Iran wood and paper (choka) factory as black liquor and another provided from Aldrich company, were studied. Firstly, the lignin was precipitated from its black liquor by a dilute acid and was then purified by dissolving in tetrahydrofuran (THF). Lignin samples were characterized using Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1HNMR) spectroscopies. It was found from results that the Aldrich lignin has a structure similar with the lignosulfonate while lignin extracted from black liquor does not have a hydrophilic sulfonate group and has a Kraft lignin structure. Using acetylation of Kraft lignin and complementary characterization with 1HNMR spectroscopy, the ratio of hydroxyl functional groups to methoxy groups was calculated to be 1.11 to 1, and amount of the hydroxyl groups was calculated to be 5.91 mmol/g of acetylated lignin, where 53% of the hydroxyl groups is related to the aromatic hydroxyl groups. By having the molecular weight of the Kraft lignin which was obtained from the gel permeation chromatography (GPC) analysis of the acetylated Kraft lignin to be 1260 g/mol, average number of the hydroxyl groups per acetylated lignin chain was calculated to be 7.44.

The insertion of dowels into solid wood for furniture has been used for centuries. Recently, this simple technology has been upgraded. The objective of the research was to evaluate and compare the tensile strength of the joints made of wood dowel through new method “wood welding” and classical method “using of glue”. Variables included dowel joints method (welding joint and joint with glue), dowel diameter (10 and 12 mm) and dowel surface (smooth and grooved). Members joint and dowel wood were hornbeam species (Carpinus betulus) and the used glue was polyvinyl acetate (PVA). The results showed that the types of joints, diameter and surface dowel, have significant effect on the tensile strength, so that welded joints, dowel diameter 12 mm and dowel grooved surface has the most tensile strength to other samples. The results also showed that in all cases, the strengths of the joints made by welding was more than the joints made by PVA glue.

The Use of agricultural plants wastes as an alternative forest resources in the cellulose industry can be recommended due to the severe shortage of wood raw material and restriction of forest harvesting. The aim of current research was to investigate the effect of thermal modification on applied properties of composite made from sunflower stem flour-polypropylene. Thermal modification of sunflower stems was done at temperatures of 160, 180 and 200°C for 30 minutes and mixed with polypropylene in ratio of 30wt%. Test samples were prepared with maleic anhydride-grafted polypropylene as coupling agent by injection molding method. FTIR spectroscopy of sunflower stem flour confirmed the chemically changes due to thermal modification. More integration and uniform distribution, and less cavities were observed in the scanning electron micrographs of failure surface. The removal of hemicellulose of sunflower stem flour improved the thermal stability of composite, which thermal gravimetric analyzer (TGA) confirmed it with increasing in modification temperature up to 180°C. Modification at 200°C decreased thermal stability compared to other temperatures. Thermal modification leads to significant decrease in water absorption and improvement in bending and tensile properties due to hemicellulose degradation, increasing the crystallinity, loss of polarity, increased compatibility between the two phases of composite and uniform distribution of fillers in polymeric matrix. Notched impact strength of modified composites decreased due to better adhesion between lignocellulosic filler and polymer that facilitate the crack development along the interface.

Although many studies have been done about the application of waste materials such as used plastics but returning of wood plastic products (Regrind) to the production cycle was rarely reported. In this work, the effect of once and twice regrind on the functional properties of WPC made from high density polyethylene (HDPE) has been studied. The specimens were fabricated with powder raw materials and by the flat press under laboratory conditions. HDEP and poplar wood flour were mixed with a weight ratio of 50-50 percent. The estimation of regrind process, physical and mechanical properties of boards were measured after each regrinding and also to evaluate of regrinding on filler particle size and the interface between the polymer and wood flour some Scanning Electron Microscopy (SEM) were prepared. The results of this research showed that regrinding of WPC leads to a decrease in mechanical properties including bending strength, flexural modulus, tensile strength and tensile modulus and on the other hand regrinding process leads to improved physical properties including water absorption and thickness swelling after hours. SEM photographs showed that during the process of regrinding, filler particle size is reduced while matrix surrounding the filler particles better.

The effect of adding steamed and non-steamed fiber on physical and mechanical properties of the composites made of recycled polypropylene was investigated. Recycled polypropylene was used as a basic matrix at a 57% level, and poplar fibers were used at 180 °C for 1 h at a constant level of 40% in two forms: non-steamed and steamed. The ratio of steamed fibers to non-steamed fibers in composites was 100:0, 50:50, and 0:100, respectively. For all components, the coupling agent was maleic anhydride at a level of 3%. Mixing was done using an internal mixer at 180 °C and 60 rpm, and the samples were constructed by injection molding method. To investigate the effect of steam treatment on the fiber structure and crystallization, X-ray diffraction analysis and FTIR spectra were used. The results showed that the Steaming had no significant effect on resistance. But with steaming increased mechanical properties and physical properties of reduced.

In this research, the individual and interaction effects of three organic biocides (propiconazole, tebuconazole, and chlorothalonile) with the metal chelator EDTA and the antioxidant BHT at different concentrations (50, 150, 250, 350, and 450 ppm) against the white-rot fungus, Trametes versicolor was investigated. In under laminar sterile hood, about 25 mL of the media was poured into the Petri plates. Three antibiogram discs (with triangular position) put on the media. By micro-sampler about 20 μL of steriled preservative solutions was poured on every disc, separately. Then, about 5 mm of mycelium plug of intended fungus that was inoculated previously was put in the center of plates. The plates were incubated and daily for one week, the mycelium growth of fungus and inhibition effects of different preservative solutions against fungus was measured. The results of this research demonstrated that chlorothalonil biocide by itself have not any inhibition effect on growth of fungus, whilst propiconazole and tebuconazole biocides by itself have significant effect at different concentrations on growth of fungus. In consider of synergistic effect of propiconazole, tebuconazole, and chlorothalonil biocides with non-biocides additives of EDTA and BHT, it has been found that there is synergistic effect between propiconazole biocide and the metal chelator EDTA at high concentration such as 450 ppm, but in combination with other solutions synergistic effect has not been found. Also, any synergistic effect has not found between tebuconazole and chlorothalonil biocides with other preservative solutions.

One of the main strategies to develop the extent of wood modification is using active functional groups in wood structure or the so-called impregnation with modified N-methylol compound. The aim of this study was to evaluate the physical properties of paulownia wood after modify with Polycrease ECR Cell wall resin, to name modified dimethylol-dihydroxyethyleneurea (mDMDHEU). Physical test samples were prepared according to ASTM and EN standard and treated with pressure vessel method at two concentration levels; 15 and 25 percent of soluble resin. For polymerization, treated samples were heated in oven for 24-hour periods at 145 and 155 ºC respectively. Weight percent gain (WPG), bulking, water soaking, swelling, anti-swelling efficiency (ASE), leaching and contact angle were determined. High mDMDHEU concentration increased the weight gain and cell wall bulking. Highest weight percent gain (10.70%) and bulking efficiency (6.85%) in to levels of 25% were determined at 155 ˚C. In comparison with the unmodified wood, the mDMDHEU modified wood due to absorbed polymer enhancement exhibited improved dimensional stability and reduced water uptake, and maximum dimensional stability were determined in samples modified using to level 25% mDMDHEU containing solutions and curing temperature 155 ºC. Moreover, mDMDHEU treatment was resistant to leaching. Contact angle measurement further confirmed the improved hydrophobicity of wood after modification. Modification with mDMDHEU improved significantly the physical properties. The improve of the resistance of chemically modified wood exposed to can be attributed to the reduction of wood moisture, bulking of cell walls and cell cavities blocking affect to dominant reactivity mDMDHEU with cell wall wood polymer.

In this study, the reinforcing effect of recycled newsprint paper (RNP) in cement boards has been investigated. The experimental design consisted of two variable factors namely RNP and calcium chloride (CaCl2). In the sample preparation, boards with density of 0.7 kg/m3 were manufactured using fiber/cement ratios of 10:90, 15:85, 20:80 and 25:75 by weight and 3% and 5% CaCl2 as accelerator. At least four boards (replications) were fabricated for each treatment, and the mechanical and physical properties of the boards were evaluated. The statistical analysis showed that the differences between the mean values of the RNP and CaCl2 contents among each of the groups (treatments) compared were significant. Test results showed that addition of CaCl2 tends to enhance both the mechanical and physical properties of the boards. All properties of the boards were improved when the CaCl2 content was increased from 3% to 5%. The rupture and elasticity moduli of the boards decreased with an increase in the RNP content, and the maximum values were obtained at RNP loading of 10%. The results also showed that as the fiber content was increased, significant increased in water absorption and thickness swelling occurred. Increasing RNP fiber content from 10% to 25% reduced both the mechanical and physical properties considerably. The optimum condition was obtained when the RNP and CaCl2 contents were 10% and 5%, respectively.