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This research was aimed at studying the preparation of thermoplastic starch (TPS) from cornstarch flour using twin screw extrusion. Also, the effects of the addition of cellulose nanofibers (CNFs) as reinforcement, on TPS nanocomposite films properties were evaluated. Nanocomposites with 0.5, 1.0 and 1.5wt% of CNFs content were prepared. The chemical structure of starch, TPS and TPS/CNFs were characterized by Fourier-transform infrared spectroscopy (FT-IR) and X-ray diffraction. The mechanical properties, morphological structure, and thermal stability of neat thermoplastic starch and their nanocomposites were investigated by scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and water absorption (WA) test. Results showed that it was possible to improve the WA, thermal, and mechanical properties of TPS with the addition of CNFs due to its good dispersion and the interaction of CNFs with the TPS matrix. The storage modulus, loss modulus, and the tan δ peak position of TPS/CNF nanocomposites improved in comparison with the TPS matrix. These findings confirmed the enhancement of mechanical properties of TPS/CNF nanocomposites. In addition, TGA and DSC results showed that increasing CNF content improves the thermal stability of TPS-based nanocomposites. SEM images showed that CNFs dispersion within the TPS matrix was uniform and the surfaces of TPS/CNF films were smooth. The WA of the TPS/CNF composites moderately decreased with the addition of CNFs. Finally, the results obtained clearly showed the advantages of reinforcing TPS with CNFs, a natural, cheap and abundant green nanocomposite.

The main goal of this work was to reinforce softwood pulp (SP) with bacterial cellulose (BC) to generate a sustainable biocomposite. BC is a nanocellulose, which was anticipated to increase interfacial adhesion between the cellulosic fibers and BC. The organism used was Gluconacetobacter xylinus, which was incubated in a static Hestrin-Schramm culture at 28°C for 14days. The specimens of BC, SP and the reinforced SP with BC were characterized using X-ray diffraction (XRD), FT-IR, FESEM, and physico-mechanical testing. The crystallinity index was found to be 83 and 54% for BC and SP, respectively. FT-IR spectra showed that the composition of BC was fully different from that of SP fibers. Based on FESEM images, one can conclude that BC and softwood fibers do form a good combination with a nonporous structure. BC fibers fill in among the softwood fibers in the sheet. The physical and mechanical properties showed that as the dosage of BC increased, the properties of tensile index, tear index, and burst index greatly improved, while the porosity and the elongation decreased. The reason for the improved mechanical properties can be attributed to the increase of interfibrillar bonding which reduced porosity. This would be due to the high aspect ratio of BC that is capable of connecting between the cellulosic fibers and BC nanofibers, enhancing a large contact surface and therefore producing excellent coherence. This study suggests that BC could be a promising material for reinforcing composites at low loading.

The aim of this paper was to prepare composites of bacterial cellulose (BC) filled with silica (SiO2) nanoparticles to evaluate the influence of the SiO2 contents (3, 5 and 7wt%) on the thermo-mechanical properties of the composites. BC hydro-gel was immersed in an aqueous solution of silanol derived from tetraethoxysilane (TEOS), the silanol was then converted into SiO2 in the BC matrix by pressing at 120°C and 2MPa. The BC/SiO2 translucent sheets were examined by dynamic-mechanical analysis (DMA), thermo gravimetric analysis (TGA), and scanning electron microscopy (SEM). The temperature dependence of the storage modulus, loss modulus and tan delta was determined by DMA. In general, the results revealed that the increment of storage modulus and thermal stability increased concomitantly with the augmentation of SiO2 content. Therefore, it could be concluded that the mechanical properties of the composites were improved by using high amounts of nano silica. This would be a high aspect ratio of BC capable of connecting the BC matrix and SiO2, thereby enhancing a large contact surface and resulting in excellent coherence. A decrease of the storage modulus was consistent with increasing temperature, resulting from softening of the composites. The storage modulus of the composites increased in the order: BC/S7>BC/S5>BC/S3, while the loss modulus and tan delta decreased. On the other hand, the thermal stabilities of all BC/SiO2 composites were remarkably enhanced as compared to the pristine BC. TGA curves showed that the temperature of decomposition of the pure BC gradually shifted from about 260°C to about 370°C as silica content increased. SEM observations illustrated that the nano-scale SiO2 was embedded between the voids and nano-fibrils of the BC matrix. Overall, the results indicated that the successful synthesis and superior properties of BC/SiO2 advocate its effectiveness for various applications.

This article presents the preparation and characterization of walnut shell (WS)/high density polyethylene composites. The effects of nano-SiO2, as reinforcing agent, on the mechanical and physical properties were also investigated. In order to increase the interphase adhesion, maleic anhydride grafted polyethylene was added as a coupling agent to all the composites studied. In the sample preparation, nano-SiO2 and WS contents were used as variable factors. The mechanical properties, namely, the tensile, flexural and notched Izod impact strengths and physical properties, viz. the thickness swelling and water absorption of the composites were determined. The morphology of the specimens was characterized using scanning electron microscopy technique. The results of strength measurement indicated that when 2 wt% nano-SiO2 was added, tensile and flexural properties reached their maximum values. At high level of nano-SiO2 loading (4 wt%), increased population of nano-SiO2 lead to agglomeration and stress transfer gets blocked. The addition of nano-SiO2 filler slightly decreased the impact strength of composites. Overall trend shows that with addition of WS flour up to 50 wt%, tensile and flexural properties of the composites are significantly enhanced.

The aim of this research was to fabricate multilayer insulator nanocomposites using phenolic resin impregnated bacterial cellulose (BC) handsheets and investigate the relationships between their structural and electro-thermo-mechanical properties. G. xylinus was incubated in a static Hestrin-Schramm culture at 28 °C for 14 days. Then, BC aqueous suspension was added to kraft pulp aqueous suspension. The content of BC that was added to the pulp suspension was as follows: 5, 10 and 15%. The disintegrated BC was turned into handsheets by a vacuum method. Dried handsheets were immersed in phenolic resin. To obtain composites, 5 immersed handsheets from each treatment were laid-up and hot pressed at 150 °C under 100 MPa pressure for 10 min. The specimens were characterized by means of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermal mechanical analysis (TMA), field-emission scanning electron microscopy (FE-SEM) techniques and insulating tests as dielectric loss factor and breakdown voltage. The results of thermal analysis showed an improvement in the thermal stability and an increase in the evaporation enthalpy of prepared samples with higher BC content. The mechanical examinations indicated that by increasing BC content in nanocomposites, the loss modulus and tan delta increased and the storage modulus of specimens decreased. The coefficient of thermal expansion (CTE) of samples diminished with increase of BC content. FE-SEM characterization showed different qualities of resin impregnation of the papers. The results of insulating tests confirmed that dielectric loss tangent and dielectric breakdown voltage increased in the specimens with higher BC content.

The present work reports the effect of cellulose nanofibers (CNFs) on the thermal, dynamic mechanical analysis (DMA), density and water uptake of thermoplastic starch (TPS) foamed composites. The obtained thermal and DMA results illustrate that thermal stability, storage modulus (E′), loss modulus (E″) and damping factor (tan δ) increase for all TPS/CNF samples compared to the pure TPS foamed composite. The results showed that the incorporation of CNFs caused an increase in the glass transition temperature (Tg) of the TPS foamed composites. Additionally, thermal results revealed that 1.5 wt% CNF offers superior resistance or stability towards heat compared to its counterparts. Addition of the CNF filler into the TPS matrix decreased the apparent density and water absorption. Interestingly, SEM images illustrate that when a small content of rigid nano particles (1.0 or 1.5 wt%) was added in the foamed composites, the cell size decreased while the cell density increased.

The aim of this work is to evaluate performances of tannin-based resins designed as adhesive in the plywood production. For this purpose, a part of phenol formaldehyde (PF) and melamine formaldehyde (MF) in the classic adhesive formulation was replaced by tannin. The physical properties of the formulated resins (rheological characterization, etc.) were measured. In order to analyze the mechanical performance of tannin-based resins, plywood panels were produced and the mechanical properties including tensile strength wood failure and three-point bending strength were investigated. The performance of these panels is comparable to those of plywood panels made by commercial PF and MF. The results showed that the plywood panels bonded with tannin–PF (PFT) and tannin–MF (MFT) resins exhibited better mechanical properties in comparison to the plywood panels made of commercials PF and MF. The introduction of small properties of tannin in PF and MF resins contribute to the improvement of the water performance of t...

Fast growing and low-density species can be modified by various thermo-hydro-mechanical (THM) treatments. Wood densification is one of the promising techniques for broadening the application of these species. This study focuses on the use of a high-capacity continuous pressing technique that considerably increases the density in the region beneath the surface of poplar wood. Prior to densification at 185 °C, a softening stage was implemented, with water spraying followed by heating at a temperature of 205 °C to 235 °C. The density profile, set-recovery, and morphology of the densified surface were investigated. Densitometry revealed that an M-shaped density profile was created through the thickness, with a peak density of approximately 700 kg/m3 close to the surfaces. The set-recovery after three wetting-drying cycles was 44%, which revealed that partial stress relaxation occurred during the densification. Scanning electron microscopy (SEM) confirmed that both sides of the wood were successfully densified and that after the wetting-drying cycles, the deformed cells did not completely recover.

In this study, effect of nano-SiO2 on some applied properties of oriented strand board (OSB) made from underutilized low quality paulownia wood employing was investigated. Nano-SiO2 at four levels (0, 1, 3 and 5 phc) was added to urea formaldehyde (UF) resin and since nano-SiO2 has effect on the curing of UF resin, the press cycle time (7 and 10 min) was also selected as variable. Some chemical properties of paulownia wood (holocellulose, cellulose, lignin and ash contents, pH value, hot and cold water solubility), mechanical (modulus of rupture, modulus of elasticity, internal bond strength, screw and nail withdrawal strengths), physical (thickness swelling and water absorption) properties and formaldehyde emission of the strand boards were evaluated. Mechanical properties of all panels were found to comply with general-purpose OSB minimum value requirements of EN 300 Type 1 (1997) for use in dry conditions. With incorporation of nano-SiO2 up to 3 phc into UF resin mechanical and physical properties of the resulting panels improved and formaldehyde emission decreased. However, none of the panels did satisfy the WA and TS requirement of EN Standard for general purpose usage. The results of X-ray diffraction (XRD) and transmission electron microscope (TEM) analysis confirmed the good dispersion of nano-SiO2 in the resulting OSBs. Using paulownia as a fast growing underutilized species not only can sustain the forests but also can supply raw material shortage in wood short countries.

The aim of this paper was to prepare composites of bacterial cellulose (BC) filled with silica (SiO

In this research, the reinforcing effect of fillers including canola stalk, paulownia and nanoclay, in polypropylene (PP) has been investigated. In the sample preparation, 50 wt% of lignocellulosic materials and 0, 3, and 5 wt% of nanoclay particles were used. The results showed that while flexural and tensile properties were moderately enhanced by the addition of nanoclay in the matrix, notched Izod impact strengths decreased dramatically. However, with increase in the nanoclay content (5 wt%), the flexural and tensile properties decreased considerably. The mechanical properties of composites filled with paulownia are generally greater than canola stalk composites, due to the higher aspect ratio. The thickness swelling and water absorption of the composites significantly decreased with the increase in nanoclay loading. Except tensile modulus, the differences between the type of fibrous materials and nanoclay contents had significant influence on physicomechanical properties. Morphologies of the composites were analyzed using transmission electron microscopy (TEM) and X-ray diffraction (XRD), and the results showed increased d-spacing of clay layers indicating enhanced compatibility among PP, clay, and lignocellulosic material. TEM micrographs also confirmed that the composites containing 3 wt% nanoclay had uniform dispersion and distribution of clay layers in the polymer matrix. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

In this study, the suitability of walnut shell as a renewable agricultural residue for panel manufacturing was investigated. Particleboards containing different walnut shell particle ratios (0%, 10%, 20%, 30%, 40% and 100%) were made using urea–formaldehyde (UF) resin. Some chemical properties of walnut shell (holocellulose, α cellulose, lignin and ash contents, alcohol–benzene solubility, 1% NaOH solubility, hot and cold water solubility), mechanical (modulus of rupture, modulus of elasticity and internal bond strength) and physical properties (thickness swelling and water absorption) of the particleboard were determined. The addition of walnut shell particles greatly improved the water resistance of the panels. However, flexural properties and internal bond strength decreased with increasing walnut shell particle content. The results indicated that panels can be manufactured utilizing walnut shell particles up to 20% without falling below the minimum EN Standard requirements of mechanical properties for general purpose use. Conclusively, walnut shell, an annual residue, could be utilized with mixture of wood particles in the manufacture of particleboard used for outdoor environments due to lower thickness swelling and water absorption.

PurposeThe purpose of this paper is to describe the development of an eco‐friendly tannin‐phenol formaldehyde resin (PFT) applicable in the wood composite industry.Design/methodology/approachThe bark of oak (Quercus castaneifolia) contains a large amount of condensed tannin. Condensed tannin, with a large amount of Catechol groups was considered for reducing the formaldehyde emission level on the adhesive system. Physical characteristics of synthesized PFT resin were evaluated.FindingsFor optimal extraction, three solvents were used in the extraction process. The results showed that a mixture of water‐methanol (1:1 v/v) as extracting solvent is the best solvent and yields about 14 per cent tannin based on dry weight of bark. For producing tannin phenol formaldehyde adhesive, 10 per cent, 20 per cent and 30 per cent (based on PF dry weight) of PF, substituted with natural extracted tannin. For evaluating PFT performance effects of percentage amount of substitution tannin content on the gel time, viscosity, pH, and density of adhesives were evaluated. Based on emission test (JIS A 1460‐2001) formaldehyde emission of PFT 10 per cent, 20 per cent and 30 per cent were 1.13, 1.12 and 0.4 mg/100 g, which is very low compared with tannin‐free PF.Research limitations/implicationsTannin‐PF adhesive compared to PF adhesive had lower PH, higher viscosity and shorter gel time.Practical implicationsThe method developed provides a simple and excellent renewable resource “tannin” which can be used or partially substituted in phenol formaldehyde adhesive.Originality/valueResults showed that replacing PF for tannin reduces modulus of rupture (MOR) and modulus of elasticity (MOE) slightly but has significant effects on IB, water absorption and thickness swelling.

In this study, the effect of nanoclay on some applied properties of oriented strand board (OSB) made from underutilized low quality paulownia wood was investigated. Organo-modified montmorillonite (MMT) at four levels (0, 1, 3 and 5 %) was added to urea formaldehyde (UF) resin. Some chemical properties of paulownia wood (holocellulose, cellulose, lignin and ash contents, pH value and hot and cold water solubility), mechanical [modulus of rupture (MOR), modulus of elasticity (MOE), internal bond strength, screw and nail withdrawal strengths], physical (water absorption and thickness swelling) properties and formaldehyde emission of the strand boards were evaluated. Mechanical properties of all panels complied with the general-purpose OSB minimum property requirements of European Norm. With increasing 5 % nanoclay to UF resin, mechanical and physical properties of the resulting panels improved and formaldehyde emission decreased. However, none of the panels satisfied the thickness swelling and water absorption requirement. The results of X-ray diffraction and transmission electron microscope analysis confirmed the good dispersion of nanoclay in the resulting OSBs. Using paulownia as a fast-growing underutilized species not only can sustain the forests but also can supply raw material to countries facing shortage of wood.

Several composites based on recycled—virgin polypropylene, wood flour and organically modified montmorillonite (commonly called ‘nanoclay’) were prepared by melt compounding. This paper aims to evaluate the potential for the use of recycled polypropylene and underutilized wood flour as material for the development of wood–plastic composites, as well as reinforcement effect of organically modified montmorillonite on them. In order to improve the poor interfacial interaction between the hydrophilic wood flour and hydrophobic polypropylene matrix, as well as polypropylene–organically modified montmorillonite, maleic anhydride-grafted polypropylene was used as a compatibilizer. Some mechanical and physical properties were evaluated. Findings of this work show that both recycled and virgin polypropylene can be used in manufacture of wood–plastic composites and there is no significant difference in the properties of resulting nanocomposites. It was found that mechanical properties of polypropylene containing 40wt% wood flour reinforcement remain essentially unchanged when the virgin polypropylene in the matrix is replaced be recycled polypropylene. Morphologies of the nanocomposites were analyzed by scanning electron microscopy and X-ray diffraction, and the results showed increased d-spacing of clay layers indicating enhanced compatibility between polypropylene and clay and wood flour. Consequently, polypropylene recycled from postconsumer applications can be used in high-value nanocomposites without going the expense of separating out impurities from the polymer.

In present study, the suitability of using waste timber railway sleepers (WTRSs) as filler in wood–cement composites was investigated. The effects of two variable factors namely press temperatures (25 and 60 °C) and calcium chloride contents (3%, 5% and 7% w/w cement) on some physico-mechanical properties were also investigated. The following experimental parameters were constant: wood/cement ratio (40:60), board thickness (15 mm), press pressure (40 kg/cm2), and press time (5 min). Press temperature, calcium chloride and the interaction of both variables had significant effects (p

This study investigated the effects of organoclay platelet contents (0, 3 and 5 wt%) and polypropylene type (virgin and recycled) on the mechanical properties of polypropylene/wood flour composites. Composite samples were made by melt compounding and consequent injection moulding. The tensile, flexural and impact properties of resultant composites were determined. X-ray diffraction (XRD) analysis of composites with 3 and 5% nanoclay content was also conducted. The results indicated that tensile and flexural properties of the composites increased with the addition of nanoclay particles up to 3 wt% and decreased thereafter. The impact strength of the composites, however, decreased with the incorporation of nanoclay. The mechanical properties of the recycled polypropylene-based nanocomposites were statistically comparable with those based on virgin polypropylene. XRD analysis revealed that the degree of intercalation in the nanocomposites containing 3% nanoclay was higher than in those containing 5%. Based on these results, it can be concluded that recycled polypropylene could be used instead of virgin polypropylene in the production of value-added products with no significant adverse effects on the mechanical properties.

In this study the effect of nanoclay (0, 3 and 5 wt %) and grafted anhydride maleic with polypropylene (MAPP, 3 and 5 wt%) on physical and mechanical properties of polypropylene/wood flour nanocomposite was investigated. For manufacturing of these composites after melt compounding of the material they were converted to wood plastic granules in extruder and placed in hot press. The results showed that with increase of nanoclay physical (thickness swilling and water absorption) properties increases significantly but mechanical (bending and module of elasticity) properties increase up to 3 percent but after that gradually decreases. Also with incorporation of MAPP physical and mechanical properties of this nanocomposites improved and this positive effect was stronger for 5 percent MAPP than 3 one.

The aim of this study was to determine the performance of three-layer particleboard made from wheat straw and veneer splinters, as waste materials. For the purpose of evaluation, compositions of wheat straw and beech veneer splinters at different mixture rates were compared for some of properties. Physical (thickness swelling and water absorption) and mechanical properties (modulus of rupture, modulus of elasticity, internal bond and impact strength) of the boards were evaluated. Effects of mixing ratios of fibrous material and press temperature on the above-mentioned properties were also investigated. The mixing ratios of beech veneer with wheat straw were 100%:0%, 75%:25%, 50%:50%, 25%:75% and 0%:100%, respectively. A commercial urea–formaldehyde (UF) adhesive was used as binder. A total of 10 experimental boards with an average target density of 0.70 g cm−3 across all mixtures were fabricated. All the mechanical and physical properties of the boards were improved when the press temperature was increased from 140 to 170 °C. Analysis of data revealed that the mechanical properties were significantly different among the board types. With the exception of modulus of elasticity, the other properties were decreased by the addition of wheat straw particles. In general, water absorption and thickness swelling decreased with the increase of wheat straw content. The presence of wheat straw in the particleboards resulted in higher water absorption and thickness swelling. Finally, it can be stated that wheat straw and beech veneer splinters have potential as supplement fibrous materials, in combination with wood particles for particleboard manufacturing and indoor applications.

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 (CaCl 2 ). In the sample preparation, boards with density of 0.7 kg/m 3 were manufactured using fiber/cement ratios of 10:90, 15:85 and 20:80 by weight and 3% and 5% CaCl 2 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 CaCl 2 contents among each of the groups (treatments) compared were significant. Test results showed that addition of CaCl 2 tends to enhance both the mechanical and physical properties of the boards. All properties of the boards were improved when the CaCl 2 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 20% reduced both the mechanical and physical properties considerably. The optimum condition was obtained when the RNP and CaCl 2 contents were 10% and 5%, respectively.

In this study the effects of growth times and culture mediums on the structural characteristics of bacterial cellulose have been investigated. Bacterial cellulose (BC) nanofibers were synthesized by Gluconacetobacter xylinus. BC pellicles were compared using SEM, FT-IR and X-ray diffraction techniques. The crystallinity index (CrI) and crystallite size (CrS) were calculated based on X-ray measurements. Three growth times (7, 14 and 21 days) and three culture mediums (A, B and C) were applied. SEM micrographs showed that increasing growth time up to 7 days improves the microfibril branches crossing to each other and the number of bundles. However, further increase in growth time (21 days) results in decrease in the microfibril network. On the other hand the hydrogen and C–H bonds were developed by the increase in growth time. In conclusion, BC synthesized in medium B for 7 days had superior properties in terms of CrI, CrS and microfibril networks.

This study was carried out to explore the possibility of making cement-bonded wood–wool composite building products using eucalypt (Eucalyptus camaldulensis) and poplar (Populus deltoides). The experimental design consisted of three treatments – ratio of wood–wool mixture, percentage concentration of cement, and calcium chloride (CaCl2). The mechanical properties in terms of modulus of rupture (MOR), modulus of elasticity (MOE) and internal bond (IB) strength were investigated. The ratios of wood–wool to cement were 40:60 and 60:40 by weight. The addition of the woody material to cement clearly reduced the maximum hydration temperature and increased the time to maximum temperature. Eucalypt was generally less compatible with cement than poplar wood. Test results showed that boards made with poplar wood–wools had superior properties compared to the eucalypt and mixed wood–wools. The presence of eucalypt in mixture of woody materials typically resulted in decrease in mechanical properties. It has been noted that a dose of 5% of CaCl2 by weight of cement can enhance the effect of cement. Application of Duncan's Multiple Range Test for the mean values of the results showed that the effects of all variables and their interactions on the mechanical properties in terms of MOR, MOE and IB were highly significant (p ≤ 0.01%). The mechanical properties of most produced boards were found to satisfy the minimum requirements of ISO standard.

The main objective of this study is to investigate some of applied properties of experimental particleboard panels made with bagasse, as an alternative fibrous raw material. Modulus of elasticity (MOE), modulus of rupture (MOR), internal bond strength (IB) and thickness swelling (TS) of the specimens were evaluated. In addition, average roughness (Ra) and mean peak-to-valley height (Rz) were used to determine quantitatively surface characteristics of the panels. Three-layer mats with target density of 0.70 g/cm 3 were formed by using fine chips for the face layer (25 wt.%) and coarse chips for the core layer (50 wt.%). Variable factors were as wood species (bagasse, poplar and mixed hardwood species), moisture content of mat (face layer: 12%, 14% and core layer: 9%, 11%) and press time (6 and 8 min). Statistical analysis showed that all variable factors exerted a significant influence on MOR, MOE, IB, TS, Rz properties of the boards as a single factor. Panels made with bagasse particles had superior mechanical and physical properties compared to the poplar and mixed hardwoods particles. Bagasse boards exhibited better surface roughness, having lower Ra and Rz values, than those made with poplar and mixed hardwoods particles.

This study was carried out to explore the possibility of making cement-bonded composite building products using eucalypt (Eucalyptus camaldulensis) and poplar (Populus deltoides). The experimental design consisted of three treatments—mixture of fibrous materials, cement and calcium chloride (CaCl2) contents. Some physical properties, vis. water absorption (WA) and thickness swelling (TS), were investigated. The ratio of woodwool : cement was 40:60 and 60:40 by weight. Results showed that, water uptake increased with increasing woodwool content. In addition, boards fully made with poplar woodwools had superior properties compared to the eucalypt and mixed woodwools. The presence of eucalypt woodwools in mixture of fibrous materials typically resulted in increase in TS and WA. It is interesting to note that a dose of 5% of CaCl2 by weight of cement can enhance the effect of cement. Application of Duncan’s Multiple Range Test for the mean values of the results showed that the effects of all variables and their interactions on the mechanical properties in terms of TS and WA were highly significant.

The objective of this work is to evaluate the mechanical and physical properties of three-layer boards made with wheat straw and bonded with a tannin-based adhesive. The mechanical properties of panels were evaluated by the static bending (modulus of rupture – MOR and modulus of elasticity – MOE) and the internal bond (IB) tests. Physical properties such as water absorption (WA) and thickness swelling (TS) in water were determined. In general, all types of straw panels made produced in this work met the MOR, MOE, IB and TS requirements for general uses according to European standards. Although, wheat straw boards made with tannin-modified PF resins had slightly poorer mechanical properties compared to the boards made with pure PF, the T 10% PF resin showed higher bond ability than other modified PF resins. The highest MOR, MOE, IB and the lowest WA and TS were achieved at a 12 min press time and by using T 10% PF resin. An increase in the press time positively affected the physical and mechanical properties of the panels produced. With respect to the findings of this study, it may be stated that wheat straw can be used as a promising raw material for panel production with the use of a tannin-modified PF adhesive.

The purpose of this study was to determine some physical and mechanical properties of sandwich panels manufactured from the core of Paulownia wood and surfaces of multilayer of fiberglass and resins. Paulownia was selected among Hardwoods because of its s low density (0.26 g/cm3) and high strength/weight ratio. Eight treatments were used for experiments: Two kinds of fiberglass (needle and combination of the needle and curtain type), two various resins (polyester and epoxy) and two core thicknesses (9mm and 19mm). Physical properties including density, resistance to water absorption, Dimensional stability, and Mechanical Properties such as internal bonding, compressive and bending strength of panels were measured following ASTM Standard. The results indicated that panels with 19 mm thick core had lower density (0.5g/ cm3) compared to the 9mm thick panels (0.7g/cm3). Bigger volume of wood in the core of panels with higher thickness was the main reason of this result. The experimental results showed that thickness of wood was effective on the modulus of rupture, modulus of elasticity, and compressive strength, significantly. Epoxy resin presented higher internal bond compared to the polyester resin. The two kind of fiberglass (needle one and the combination of needle and curtain type) didn’t have noticeable differences on mechanical properties. It also was found that Paulownia is a promising species for manufacturing sandwich panel.

Regarding conservation policies of natural forests and environmental concerns forced wood composite panel manufacturers to consider using other lingo-cellulosic resources. Plantation fast growing species such as poplar, eucalyptus , paulownia and others is already started in many countries. Fast growing trees usually produce light wood with low strength so manufacturer has low certainty on using them for manufacturing wood composite panel. This study oriented toward examination of application of paulownia wood particle for manufacturing wood composite panel. In this study, specific press pressure at two levels (30 bar and 40 bar) , and press time at two levels (8 and 12 minutes) were used as independent variables. 12 experimental panels were made in laboratory. Mechanical properties such as MOR, MOE and IB were evaluated. Results showed that panels made at press pressure of 40 bar and press time of 12 minutes presented the highest MOR (41.28 MPa) and MOE (4128 MPa) but the highest IB (1.14 MPa) was observed in composite panels made at press pressure of 30 bar and press time of 8 minutes. Based on EN Standard MOR of Particleboard ranged from 12 to 15 MPa and MOE ranged from 2500 to 3000 MPa and IB ranged from 0.4 to 0.6 MPa . Comparing Above mentioned values with EN values it can be seen that Mechanical properties of wood composite panels made from paulownia are much higher than EN standard. These results are very good ground to focus on fast growing species such as paulownia to compensate wood raw material shortcoming in wood industry.

In this study, wastes of wood cutting mills (wood flour) as well as wastes of textile industry (granules of polypropylene) were used in manufacturing wood-plastic composites. Hence, wood flour with weight percent of 30, 35 and 40 was mixed with corresponding amount of polypropylene and coupling agent, polypropylene grafted maleic anhydride in amount of 6 percent was used in whole compounds. Production was done by batch method and with employment of hot press and after preparation and cutting of specimens physical and mechanical properties of them was studied. The results showed that with increase of wood flour up to 35 percent, MOR, MOE, water absorption and thickness swelling increases but further than it mechanical and physical properties decreases. Besides, increase of wood flour up to 40 percent increased the hardness of the specimens.

The aim of this study is to investigate on manufacturing new tannin phenol-formaldehyde resin as adhesive in paulownia composite. For this purpose, renewable tannin was introduced in the classic adhesive formulation in order to supply a part of phenol–formaldehyde (PF). Variables were substituted tannin with phenol at two levels (0%, 10 % and 20%) and press temperature (150Co and 170Co). plywood panels were manufactured in laboratory. Mechanical (MOR and MOE and) and physical (TS and WA) properties of panels were evaluated according to ASTM standard. Data collected based on factorial design and using SPSS software were analyzed. The Results showed that substitution tannin with phenol had slight effect on mechanical properties but when press temperature increased mechanical properties were improved. Physical properties of plywood panels bonded with tannin–PF resins (20:80) were better than plywood panels PF made.

In this study feasibility of using of mixture of bagasse and industrial wood particles for producing single and three layer particleboard . The aim of this study was to consider bagasse as partially substitute particleboard industry raw material. Variables were type of board at two levels (single and three layer), percentage of added bagasse to industrial particles at 4 levels (20%,30%, 40% and 50%) , and press temp. at two levels (165OC and 180 OC ). In producing three layer particleboard wood and bagasse particles were separated and placed in different layers so that bagasse particles were located in the face layers and wood particles were placed in the core of board. But in one layer particleboard bagasse and wood particles were used in the form of mixture. Effect of variables on physical and mechanical properties of particleboard were determined. Results showed that in three layer particleboard physical and mechanical properties were better than single layer particleboard. Increasing press temperature caused improvement in particleboard properties in most cases due to intermeshing and increasing softening wood and bagasse particles. The optimum treatment in this study was found to be adding 50% bagasse and press temperature of 180 OC.

This research was conducted to investigate the suitability of reed (Arundo donax) as a substitute for wood in laboratory made 3-layer particleboard in order to supplement the supply of raw material for the Iranian particleboard industries. The ratio of the mixture of reed and wood particles were 20:80, 30:70, and 40:60, respectively, in the surface and middle layers. Press temperatures were chosen at two levels of 165 and 185 °C. Three levels of urea formaldehyde resin were selected for the surface layers, namely: 8, 10, and 12 percent. The experimental panels were tested for their mechanical strength including modulus of elasticity (MOE), modulus of rupture (MOR), internal bonding (IB) and physical properties (thickness swelling and water absorption) according to the procedure in DIN 68763. In general, the results show that reed has a positive effect on the mechanical and physical properties of boards. In this research, the treatment with 40% reed, 12% resin in the surface layers and a 185 °C press temperature has resulted in an optimum reed board product.

Wheat straw particleboards were made using urea-formaldehyde (UF) and acrylated epoxidized soy oil (AESO) resins with two resin content levels: 8% and 13%, and three pressing times: 8, 10 and 12 minutes. Physical and mechanical properties of the boards were investigated. Results showed that AESO bonded particleboards had higher physical and mechanical properties than UF bonded boards, especially in terms of internal bond strength and thickness swelling. All properties of AESO bonded boards increase by increasing both the resin content and pressing time; but for UF bonded boards, there is a reduction in properties at 12 min pressing time due to the UF bonds destruction. AESO bonded boards can compete with wood particleboards according to EN-standards. The good properties of these particleboards are because of high compatibility between wheat straw particles and AESO resin due to its oil based structure.

As most wood-based composite products are made by compressing wood in the transverse direction, usually at elevated temperature, stress-strain response of wood under this stressing mode has a great influence not only on the design of the manufacturing process, but also on the end product properties. This paper describes a study to develop a mechanics-based method of predicting the complete stress-strain response of wood under radial compression, based on material properties of the cell wall and the dimensions of the cellular structure. The basis of the method is two previously developed micro-mechanical models for predicting gross elastic modulus and yield stress of wood under radial compression. Verification tests were conducted using white spruce specimens. It is demonstrated that using these two models, the entire stress-strain response encompassing the elastic, plastic and densification regions can be predicted with good accuracy.

The objective of this study was to investigate some mechanical (modulus of rupture, modulus of elasticity and internal bond) and physical (thickness swelling and water absorption) properties of wood-based three-layer particleboard containing different cotton (Gossypium hirsutum L.) stalks and underutilized paulownia (paulownia fortunie) wood particle ratios (30, 50 and 70%) using urea formaldehyde resin. Addition of cotton stalk and paulownia wood in particleboard improved mechanical properties of resulting composites boards significantly. However, the water resistance decreased with increasing cotton stalk and paulownia wood particle contents. The highest mechanical properties were obtained at cotton stalk and paulownia wood particle loading of 50 and 70%, respectively. Conclusively, valuable underutilized natural resources, cotton stalk and paulownia wood can be used with the mixture of industrial wood particles in the production of particleboards with high mechanical properties.Keywords: Wood, resin, urea-formaldehyde, mechanical properties, physical properties

The preparation and characterization of bacterial cellulose (BC)/silica nanocomposites are presented in this paper. BC hydro-gel was immersed in an aqueous solution of tetraethoxysilane (TEOS). By pressing the treated BC matrices at 120 °C and 2 MPa, water-free translucent sheets were obtained. TEOS concentration (3, 5 and 7%) and press time (8, 10 and 12 min) were used as variable factors. These materials were characterized by different techniques, namely FE-SEM, FTIR, SEM, tensile strength and Young's modulus. All composites showed good dispersion of the fibers and strong adhesion between the fibers and the matrix. FE-SEM observations showed that the nano-scale silica was embedded between the voids and micro-fibrils of the BC matrix. Reflecting this structure, the maximum Young's modulus and tensile strength of dry BC/silica composites improved to 1.46 GPa and 113 MPa, respectively. The tensile strength and Young's modulus showed 35 and 18-fold increase (with 7% TEOS), respectively, while the same properties were reduced 15 and 10-fold with increase in press time from 8 to 12 min. FTIR results illustrated strong chemical interactions between the cellulose and silica phases. The optimum condition was obtained when the TEOS dosage and press time were 7% and 8 min, respectively.

This study was carried out to explore the possibility of making cement-bonded wood composite building products using poplar ( Populus deltoides ) chopped strands. The experimental design consisted of two treatments namely wood strand and calcium chloride contents. Boards measuring 450 × 450 × 15 mm 3 were manufactured using wood/cement ratios of 40:60, 60:40 and 70:30 by weight and 3% and 7% of an accelerator (CaCl 2 ⋅H 2 O). At least four replications were fabricated for each treatment, and the mechanical properties and water absorption of the boards were evaluated according to DIN 68763. The mechanical properties in terms of modulus of rupture, modulus of elasticity, internal bond and impact strength were investigated and compared to the neat cement controls. Test results showed that addition of CaCl 2 tends to enhance both the mechanical and water-resistance of wood–cement composites. The bending and impact strengths of the wood–cement specimens increased with an increase in the wood content, and the maximum values were obtained at wood loading of 60% by weight. The negative influence of wood content on the internal bond can be explained by the reduced bonding ability because of weaker wood strands compared to cement. Water absorption and internal bonding were inversely proportional to the increase of cement mixture ratio, and their values increased proportional to the increase of wood ratio in the mixture. In addition, all properties of the boards were improved when the CaCl 2 content was increased from 3% to 7%.