Iranian Journal of Wood and Paper Science Research
Year:2020 | Volume:35 | Issue:1 (70)|Papers Count:10

This research was carried out with aim of investigating the effect of nano-clay (NC) addition to wood plastic composite (WPC) compound made of medium density fiberboard (MDF) and particleboard (PB) wastes and recycled polypropylene and polyethylene (HDPE) on its mechanical, thermogravimetric (TGA) and morphological properties of. For this purpose, MDF and PB waste at 50 wt. %, recycled PP and HDPE at 50 wt. %, maleic anhydride grafted with polymers at 3 wt. % and nanoclay at three different levels 3, 6, and 9 wt. % were blended using twin roll extruder. Then, standard test pieces were made using an injection molding machine and their mechanical properties and TGA thermograms were determined. Scanning electron microscope (SEM) was used to investigate the quality of nanoclay particles dispersion in the matrice as well as the lignocellulosic and polymers bonding. The results showed that tensile and flexural strength and their modulus of HDPE and PB composite significantly were increased by adding NC up to 3 wt. %, but the strengths were dropped in WPC's by increasing of NC content at 6 and 9 wt. %. The notched impact strength of WPC was decreased by NC addition indicating higher fracture surface on WPC's. SEM micrographs revealed that porosity and cavities in WPC's were decreased at 9 wt. % NC, whereas clearly showing inappropriate dispersion and aggregation of NC in WPC. The thermal stability of WPC's was slightly improved at 3 wt. % NC and the residual after combustion increased compared to the control.

In this research, the effect of sodium peroxide and sodium hypochlorite on the chemicalmechanical pulp (CMP) bleaching has been investigated. For this purpose, unbleached CMP pulp was obtained from Mazandaran wood and paper mill, and bleaching with hydrogen peroxide and sodium hypochlorite was carried out in two levels of 3 and 4%, for two times of 60 and 90 minutes at 70° C and 8% consistency. In each treatment, 30 grams of pulp was mixed with hydrogen peroxide, sodium silicate, DTPA, sodium hydroxide and sodium hypochlorite and bleaching was performed. Then, 60 gr/m 2 hand sheets were prepared and the optical properties of hand sheets were measured and analyzed based on TAPPI test methods. The results of optical properties of handsheets showed that by increasing the bleaching time and the level of chemicals, the optical properties were improved. The highest brightness and minimum yellowness were observed applying 4% hydrogen peroxide and 90 minutes in bleaching. The lowest opacity was observed in the control sample. Strength properties such as tensile, burst and tear strength of bleached paper were also increased.

In this study, paper and nanopaper were first produced and then treated with dodecyltriethoxysilane to prepare water repellent paper and nanopaper. As the result of silane treatment, the hydrophilic surface of paper and nanopaper changed to hydrophobic ones. The FESEM micrographs confirmed the nano-scale size of cellulose nanofibers. XPS results showed the presence of silane on the surface of specimens. With the treatment of silane, the water droplet contact angle increased to 104 and 153 degrees in nanopaper and paper, respectively. Therefore, the surface of treated paper can be regarded as super hydrophobic surface. TGA confirmed that the ash content of treated specimens was higher than those of untreated ones and also it was revealed that the silane treatment generated multi-layers coating on the surface of specimens. The treated specimens showed less water absorption and higher mechanical properties than untreated ones. The silane treatment made produced hydrophobic surfaces on cellulose paper and nanopaper which can led to the development of their applications for humid conditions.

Dynamic and static elastic properties of wood joints were assessed. Conventional joints, namely dovetail, tongue and groove were prepared with Fir (Abies alba) using polyvinyl acetate and cyanoacrylate adhesives. Dimensions of research samples were determined 24×50×360 (mm) according to international standard (ISO No. 3129), and the results indicate that the effects of joint type, adhesive type, joint size, and assessing the interaction of effective factors, the joint size × joint type was significant at the 5% level in dynamic and static tests. As the length of groove and height of dovetail increased in the joints, dynamic and static modulus of elasticity increased, and in terms of changes in modulus of elasticity in this research. The modulus of dovetail joint elasticity, its homogeneous joint texture, and lack of an extended adhesive line, corresponded to that of the jointed samples. Application of cyanoacrylate adhesive led to higher modulus of elasticity, compared to samples glued with polyvinyl acetate adhesive. The results of the Student's t-test indicate that there exists a not significant difference between the mean of dynamic and the mean of static modulus of elasticity, not significance at 5% level and The Pearson correlation test indicate that the dynamic and static modulus of elasticity of the samples are significant at 5% level and are of positive correlation(+0. 958). With regard to the correlation of the results of dynamic and static tests, methods for non-destructive dynamic investigation may be regarded as appropriate alternatives to destructive static tests, in order to assess and classify woods.

The aim of this study was to investigate the effect of poplar wood impregnation with nanowollastonite and nano-wollastonite-styrene mixture on fire resistance and mechanical properties of wood/polymer. Populus deltoids wood samples were saturated using 4% nano-wollastonite and 75% methanolic solution of styrene monomer by vacuum-pressure method. Four different wood treatments with nano-wollastonite, styrene, mixture of 1: 1 ratio of nano-wollastonite and styrene (one-step) and finally, the initial wood impregmation by nano-wollastonite and then styrene (two-stage treatment) were investigated. In this study, the fire resistance and mechanical properties of the specimens were measured. The results showed that the weight loss of wood against fire in two-stage treatment (NW+St) was 61. 38% and in one-stage treatment (NW/St) was 69. 68% lower than control. NW/St treatment flame durability was approximately equal to NW treatment and improved by 30% compared to control. The reduction of carbonized area in twostage (NW+St) and one-stage (NW/St) treatments was 28. 53% and 29. 06%, respectively, which showed a significant decrease. The results of mechanical tests showed that the NW/St treatment had the highest value due to the presence of condensing material in parallel to the NW/St treatment which showed an increase of 57. 41% compared to the control sample. The modulus of elasticity and disruption of NW/St treatment increased by 26. 77% and 35. 71%, respectively. In addition, resistance to hardness of NW/St treatment increased by 10. 07% compared to control. Overall, it can be concluded that mixing nano-wollastonite with styrene, while increasing the polymer wood fire resistance, also improved the mechanical properties of the polymer wood.

The aim of this study was to investigate the effect of cellulose nano-fibers and chitosan on optical and mechanical properties of chemi-mechanical pulp. For this purpose, the bleached CMP pulp produced at Mazandaran Wood and Paper Industries (MWPI) was randomly selected as research sample. The cellulose nanofibers in the form of white gel was used at 3 levels of 0, 2, and 3%. The chitosan was then added to the CMP pulps suspensions at 5 levels of 0, 0. 5, 1, 1. 5, 2%, as well. Hand-sheets with a basis weight of 60 gr/m 2 were prepared from the treated pulps. The optical and mechanical properties were then measured and compared using TAPPI standard test methods. The results showed that by adding chitosan, tear, tensile, burst strength and breaking length, air resistance, yellowness, and greenness increased and brightness, Cobb 60 and a* factor decreased. On the other hand, with the addition of chitosan and nano-cellulose to CMP pulp, the tensile, burst, bre strength aking length, air resistance, Cobb 60, yellowness and a* factor increased and the tear, brightness, and opacity decreased. Moreover, the findings showed that by simultaneous addition of 2% chitosan, and 3% cellulose nanofibers to the CMP pulp, most of the paper properties were improved. Therefore, it can also be introduced as the best treatment.

In production of paperboards especially the ones with high grammage, limitation of pulp drainage will drastically reduce the speed of papermaking process. In this manner, one of the common ways to improve the drainage and subsequent increasing of machine speed is producing the multilayer paperboards can be the addition of suitable additives. . Although these layers are bonded to each other without applying any additives, but occasionally starch has been applied between the layers for improving the internal bonds of multilayer paperboards. In this study, the effect of spraying two kinds of starch commonly used in industry (native and oxidized starch) with different dosages (0, 0. 5, 1, 1. 5 and 2 g/m 2 ) was investigated. The top layer of double layered paperboard was made of recycled printing and writing pulp and the back layer was produced from old corrugated carton (OCC) recycled fibers. Grammage of each layer was set about 100 g/m 2. The results showed that spraying native and oxidized starch improved the mechanical properties comparing to control sample (without spraying any additive). Also, the native starch showed better results in comparision with oxidized starch. Moreovere, in both native and oxidized starch, the best mechanical properties were observed by applying 1. 5 g/m 2 of mentioned additives.

Pyrolysis acid or wood vinegar is a dark liquid derived from the condensation of steam and volatile compounds emitted by thermal pyrolysis of wood or any other lignocellulosic material. In this study, a heating furnace was first designed to allow a precise temperature-time program of pyrolysis. The wood from three different species including oak, citrus and cypress were pyrolyzed under a specific temperature-time schedule. The gases emitted from the furnace were cooled and condensed in a 20 m pipe ooled with flow of cold water, and then the condensate of was dumped in a container. Pyrolysis was performed at three different temperature ranges of 200, 260 and 330 ° C. The obtained pyrolysis acids had different color and acidity depending on the temperature and spieces of wood used. Under the heating conditions used in this study, cypress had lower pyrolysis rate than hardwoods. The weight percentage gain of the treated beech and pine wood varied from 5 to 35%, which was depended on the temperature as well as the wood used for pyrolysis. Acid pyrolysis at higher temperatures resulted in higher weight percentage gain. The acid pyrolysis obtained at lower temperature was leached at higher rates from treated wood. Also the wood types used for pyrolysis had significant effect on the amount of tar from treated woods.

Since the papermaking fibers contain negative charge, some polymer additives with counterions (cationic polyeletrolyte) are added to pulp slurry, Meanwhile, due to increasd electrical conductivity (EC) in the suspension, the performance of many polyelectrolytes encounter some problems. Hence, based on water system closure, lower raw water consumption, and therefore higher EC of the pulp suspension, it is necessary to evaluate the adverse effect of polyelectrolytebased additives such as cationic starch-anionic nanosilica on paper making. In this work, the effectiveness of EC on the performance of the mentioned additive combination was investigated. The results confirmed that the EC negatively affected the performance of the wet-end additive system; although the degree of effectiveness was dependent on the type of the pulp property. Such that for low polyelectrolyte dosage and high EC, in certain properties, the positive effect of this additive system was not significant. But, in the case of some other properties such as internal bond and freeness, despite of the negative effects of high EC, the performance of cationic starch-anionic nanosilica system was significantly remarkable.

The aim of this study was to energy efficient wood cement composite. Therewfore, unique wood-cement was produced by combining wood particles and fibers with cement and monolith. The investigated product consisted of wood-cement made from recycled wood fibers and poplar wood particle with the thickness of 20 mm on both sides (outer layers) of the composite and 10 mm thick unolith in the middle of the layer. The product manufactured by this arrangement of layer had a combination of cement and Unolite properties. In this study, according to the studied variables including lignocellulosic materials and amount of additive, such as calcium chloride (Cacl) at two levels of 3 and 5%, the best specimens were prepared using 10% lignocellulosic materials. The thickness of the specimens was uniform at the two monolithic surfaces and all fabrication conditions such as discharge rate, press pressure, coalescence rate were assumed to be uniform and constant. In static bending experiment the mean maximum load force for ordinary brick failure was 3933. 26N and the maximum load for breaking the cement sample was 389/78 N However, ordinary brick showed brittle fracture, while the monolithic sample showed higher toughness and the failure is gradual. The insulation properties due to the cellulosic fibers and the monolith of the compiosite was higher than the ordinary brick.