Iranian Journal of Wood and Paper Science Research
Year:2017 | Volume:32 | Issue:3 (60) |Papers Count:15

This study investigate the effect of TCF bleaching on optical and mechanical properties of CMP pulp. Some unbleached CMP pulps were randomly selected from Mazandaran Wood and Paper Industries (MWPI). Then these pulps were bleached with two and three stage OP, OPY, PY and O(Eo)P bleaching sequences using oxygen(O), alkali extraction with oxygen (Eo), sodium dithionite(Y). Hand sheets were prepared from bleahed pulps with 70 gr/m2 basis weight and then the optical and mechanical properties were measured according to TAPPI Standard test methods and compared. The results showed that brightness, greenness, fold, tensile and tear strength were increased and opacity and a* factor were decreased. In general, the impact three stage O(Eo)P and two OP and PY bleaching sequences were more effective than P stage in improving the brightness and paper strength.

In present study, the improvement of adhesion strength of polyurethane and alkyd coatings on the poplar wood (Populus nigra) by nano-silane coating using sol-gel method for outdoor application is investigated. For this purpose, the boards with the dimensions of 15 × 10 × 2 mm were prepared according to EN 927-5. The surfaces of wood specimens were modified with Tetraethoxysilane (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 facing south and with a slope of 36 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 wood surface 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, the effects micro crystalline cellulose, and multi walled Carbon Nanotube addition on the mechanical properties of wood plastics composites is investigated. Multi walled Carbon Nanotube were added to the composite compound to evaluate and compare their suitability as reinforcement for thermoplastics. The effects of micro crystalline cellulose size (20 and 50 micron) and Multi and the loading of walled Carbon Nanotube content (0, 1. 5 and 2. 5%) on the mechanical properties were studied. The results showed that mechanical properties of the composites made with 50 microns micro crystalline cellulose and 1. 5 and 2. 5 % of Multi walled Carbon Nanotube were significantly superior to those of the 20 micron) and control samples. Addition of Multi walled Carbon Nanotube enhanced 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 composites made with Multi walled Carbon Nanotube and micro cellulose were further supported by SEM and TEM micrographs.

Paper works are severely attacked by biological agents such as fungi, bacteria and insects due to its organic nature and in archives, most of the biological destruction of paper is caused by fungi. The importance of paper works conservation has led to applying different methods to fungus removal. The chemical disinfection is the most common disinfection methods. In this research, the application of Thiophanate methyl in elimination of paper destructive fungi has been studied. Laboratory studies to evaluate the effects of Thiophanate methyl on paper and fungus included accelerated ageing, the evaluation of effectiveness of antifungal Thiophanate methyl on fungi such as Aspergillusniger, Aspergillusflavus and Penicilliurnsp and determination of antifungal stability after accelerated ageing. Examination shows that Thiophanate methyl has successfully prevented spread of fungus upon dosages of 10, 50, 100, 200 and 500 ppm. Aspergillus flavus fungus had a slight growth at 10 ppm, but no growth was observed in other dosages. Aspergillusniger fungus had no growth capacity in dosages more than 100 ppm. According to the results, treated papers are still able to control fungus growth after accelerated ageing condition. In general, the results obtained by fungus growth halo and non-growth halo indicate that all fungi are controllable in dosage of 200 ppm.

The aim of this research was to investigate the effect of black liquor and nano Graphene oxide (GO) addition to urea formaldehyde resin for making three layer particle board. In this study, the amount of black liquor 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). After blending and mat forming, the mat was pressed 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 variables on the properties was measured and analyzed at 95 percent confidence level using SPSS software and variance analysis method and factorial design. The results showed that increasing black liquor 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 liquor and Graphene oxide percent. The results show that increasing of Nano ghraphene 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 kraft paper producing factory as black liquor and another provided from Aldrich company, were studied. First, 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. The results revealed 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 the 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. Molecular weight of the Kraft lignin which was determined from the gel permeation chromatography (GPC) analysis of the acetylated Kraft lignin was 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 manufacture has been used for centuries. However, recently, this simple technology has been upgraded. The objective of the research was to evaluate and compare the tensile strength of the joints made by wood dowel using new method of “ wood welding” and classical method of “ using of glue” . Variables included dowel joints method (welding joint and joint with glue), dowel diameter (10 and 12 mm) and dowel surface texture (smooth and grooved). Members joint and dowel wood were hornbeam species (Carpinus betulus) and glue was polyvinyl acetate (PVA). The results showed that the types of joints, diameter and surface texture have significant effect on the tensile strength. The welded joints, dowel diameter 12 mm and grooved surface has the highest tensile strength compared to other samples. The results also showed that in all cases, the strengths of the joints made by welding was higher than the joints made by PVA glue.

The use of agricultural plants residues as alternative fiber 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 the properties of composite made from sunflower flour-polypropylene. Thermal modification of sunflower flour was done at temperatures of 160, 180 and 200° C for 30 minutes and then these particles were mixed with polypropylene in ratio of 30 wt%. Test samples were prepared with maleic anhydride-grafted polypropylene as coupling agent by injection molding method. FTIR spectroscopy of sunflower flour confirmed the chemical 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 flour improved the thermal stability of composite, which thermal gravimetric analyzer (TGA) confirmed it with increasing the 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. According to no significant difference between temperatures of 180 and 200° C, thermal modification of sunflower stems at 180° C is recommended for manufacturing of composites with optimum properties.

Although many studies have been done on the application of waste materials such as used plastics, but recycling of wood plastic products (Regrinding) for the production of the new product is rarely reported. In this work, the effect of once and twice regrinding on the functional properties of WPC made from high density polyethylene (HDPE) has been studied. The specimens were fabricated with powdered raw materials and the flat press under laboratory conditions. HDEP and poplar wood flour were mixed with a weight ratio of 50-50 percent. The physical and mechanical properties of boards were measured after each regrinding and also the effect of regrinding on filler particle size and the interface between the polymer and wood flour some was evaluated by Scanning Electron Microscopy (SEM). 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. On the other hand, regrinding process leads to improved physical properties including water absorption and thickness swelling after 24 hours water soaking. SEM photographs showed that during the process of regrinding, filler particle size is reduced while matrix surrounding the filler particles is better.

The effect of adding steamed and non-steamed wood flour 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 wood flour non treated and treated at 180 ° C for 1 h were sued at a constant level of 40%. The ratio of steamed wood flour to non-steamed wood flour 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 fabricated by injection molding method. To investigate the effect of steam treatment on the wood flour structure and crystallization, X-ray diffraction analysis and FTIR spectra were used. The results showed that the steaming had no significant effect on strength properties. But steaming increased mechanical properties and physical properties of composites.

In this research, the individual and interaction effects of three organic biocides (propiconazole, tebuconazole, and chlorothalonile) mixed the metal EDTA and the antioxidant BHT at different concentrations (50, 150, 250, 350, and 450 ppm) against the white-rot fungus, Trametes versicolor was investigated. The tests were done in the in vitro and using of sterilized malt extract agar in the wet autoclave. First, preservative solutions were prepared with different formulations and concentrations separately and then combined with water solvent. Under laminar sterile hood, about 25 mL of the media was poured into the Petri plates. Three antibiogram discs (with triangular position) were placed on the media. By micro-sampler, about 20 μ L of sterilized 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 at 23 ° C and 75% relative humidity and the mycelium growth of fungus and inhibition effects of different preservative solutions against fungus was measured daily for one week, . The results of this research demonstrated that chlorothalonil biocide by itself have not impose 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 order to determined the synergistic effect of propiconazole, tebuconazole, and chlorothalonil biocides with non-biocides addition of EDTA and BHT, it has been found that there exist synergistic effect between propiconazole biocide and the EDTA at high concentration such as 450 ppm, but in combination with other solutions, synergistic effect has not been found. Also, no synergistic effect was 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 by 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, 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 º C respectively. Weight percent gain (WPG), bulking, water soaking, swelling, antiswelling 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 exhibited improved dimensional stability and reduced water uptake, and maximum dimensional stability were determined in samples modified using by 25% mDMDHEU containing solutions and curing temperature 155 º C. Moreover, mDMDHEU treatment was resistant to leaching. Contact angle measurement further confirmed the improved hydrophobicity of wood after modification. Modification with mDMDHEU significantly improved the physical properties. The improve of the resistance of chemically modified wood 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 experiment was designed to apply two variable factors, RNP and calcium chloride (CaCl2). Cement-fiber boards with the density of 0. 7 kg/m3 were manufactured using fiber/cement ratios of 10: 90, 15: 85, 20: 80 and 25: 75 (w/w) and 3% and 5% CaCl2 as accelerator. Minimum four boards (replications) were fabricated for each combination of variables, and the mechanical and physical properties of the boards were evaluated. The statistical analysis showed that the effect of the RNP and CaCl2 contents on modulus of rupture of cement fiber boards were significant at 1% significant level. The results showed that addition of CaCl2 enhanced the mechanical properties of the boards. All properties of the boards were improved as the CaCl2 content was increased from 3% to 5%. The modulus of rupture and modulus of elasticity of the boards decreased with addition of RNP, and the maximum values were obtained at RNP loading of 10%. The results also showed that as the fiber content was increased, significant increase 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.