Effect of press cycle time and resin content on physical and mechanical properties of particleboard panels made from the underutilized low-quality raw materials

In this study, the influence of press cycle time and resin content (RC) on some of the physical and mechanical properties of single-layer particleboard manufactured from the low-quality raw materials were determined. Eucalyptus (Eucalyptus camaldulensis), mesquite (Prosopis juliflora), saltcedar (Tamarix stricta) and date palm (Phoenix dactylifera) wood, which is underutilized invasive species in southern parts of Iran, were used as alternative raw materials for particleboard manufacturing. Variable factors were as resin content (9, 10 and 11%) and press time (PT) (4, 5 and 6 min). Other parameters such as type of resin (UF), hardener content (2%), type of hardener (NH₄Cl), press-closing time (4.5 mm/s), board density (0.75 g/cm³), press pressure (30 kg/m²) and press temperature (160 °C) were held constant. The experimental panels were tested for their mechanical strength including modulus of elasticity (MOE), modulus of rupture (MOR), internal bonding (IB) and physical stability properties (thickness swelling) according to the procedures defined by European Union (EN) Standard. Overall results showed that most panels made from above-mentioned materials exceed the EN Standards for IB, MOE and MOR. The mechanical properties of particleboard were improved as the resin content increased from 9 to 11%. The results indicated that the polymerization of resin and wood is better at 11% resin content and 5 min of press time. However, thickness-swelling (TS) values were higher (poor) than requirements. Panels made of mesquite, saltcedar and date palm with a resin content of 11% and pressed for 5 min is adequate for general uses while eucalyptus with a resin content of 11% and pressed for 6 min is suitable for interior decoration.     

Properties of medium-density particleboard from saline Athel wood

The Athel tree, Tamarix aphylla (L), can potentially be used as a biomass crop to help manage saline subsurface drainage water in arid land irrigated agriculture. In this study, Athel wood was used to manufacture medium-density particleboard with an aim of developing new applications for the saline wood. The research investigated the effects of different types of adhesives, particle sizes, bark content (BC), resin content (RC), and hot water pretreatment on the mechanical and water resistance properties of the Athel-derived, medium-density particleboards. The measured mechanical properties included tensile strength (TS), modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond strength (IB) of the finished particleboards. Water absorption and thickness swell were used to evaluate the water resistance. Polymeric methane diphenyl diisocyanate (PMDI) resin made particleboard of better mechanical properties and water resistance than urea formaldehyde (UF). The medium size (20–40 mesh) particles gave the best mechanical properties and water resistance than of the particleboard when evaluated against the smaller size (40–60 mesh) and larger size (10–20 mesh) particles. The mechanical properties of particleboard were improved as the resin content of the UF-board increased from 7 to 16%, but deteriorated as the bark content increased from 0 to 16.2%. The particleboard made from the wood particles that had undergone hot water pretreatment had poor mechanical properties and water resistance compared with the particleboard made from the untreated particles. Saline Athel wood is an appropriate material for manufacturing particleboards.     

Influence of impregnating wood particles with mimosa bark extract on some properties of particleboard

In this study, influence of impregnating wood particles with mimosa bark extract on the some properties of particleboard was investigated. Properties evaluated were modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), thickness swelling (TS), and formaldehyde emission (FE). The results showed that particleboards made from particles impregnated with mimosa bark extract had significantly lower mechanical, physical and formaldehyde emission values than those of the boards made from unimpregnated particles. Brushing of mimosa bark extract to the surfaces and edges of the particleboards did not affect the mechanical properties, statistically. However, this application caused a significant improvement in the thickness swelling and formaldehyde emission.     

Wood-wool cement board using mixture of eucalypt and poplar

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.     

Manufacture of non-resin wheat straw fibreboards

Wheat straw was used as raw material in the production of fibreboards. The size-reduced straw was pretreated with steam, hot water and sulphuric acid before the defibration process to loosen its physical structure and reduce the pH. No synthetic binder was added. Adhesive bonding between fibres was initiated by activation of the fibre surfaces by an oxidative treatment during the defibration process. Fenton’s reagent (ferrous chloride and hydrogen peroxide) was added. Two different levels of hydrogen peroxide (H₂O₂), 2.5% or 4.0% were used. The resulting fibres were characterized in terms of fibre length distribution, shive content, pH and pH-buffering capacity. The properties of finished fibreboards were compared with medium-density fibreboard (MDF) with density above 800 kg/m³ produced from straw and melamine modified UF resin. The modulus of rupture (MOR), modulus of elasticity (MOE) and internal bond (IB) were lower than those of conventional manufactured wheat straw fibreboards but close to the requirements of the MDF standard (EN 622-5: 2006). The water absorption properties for the H₂O₂ activated straw fibreboards were relatively high, but were reduced by 25% with the addition of CaCl₂ into the defibrator system as a water-repelling agent. Increased levels of hydrogen peroxide improved the mechanical and physical properties of the straw fibreboard.     

Feasibility of using eggplant (Solanum melongena) stalks in the production of experimental particleboard

This study examined possible feasibility of eggplant (Solanum melongena) stalks in the production of particleboard. Three-layer experimental particleboards with density of 0.53, 0.63, 0.73 and 0.78 g/cm³ were manufactured from eggplant stalks using certain ratios of urea formaldehyde (UF) and melamine urea formaldehyde (MUF) adhesives. Modulus of elasticity (MOE), modulus of rupture (MOR), internal bond strength (IB), thickness swelling (TS) properties of the boards were evaluated and a statistical analysis was performed in order to examine possible feasibility of these stalks in commercial particleboard manufacturing. The experimental results have shown that production of general purpose and furniture grade particleboard used in dry conditions using eggplant stalks is technically viable. The results of the study demonstrate that eggplant stalks can be an alternative raw material source for particleboard industry.     

竹材铜唑防腐剂处理工艺及力学性能研究

以竹材为试验材料,采用新型水溶性铜唑(Copper Azole,即CuAz)防腐剂对其进行防腐处理,分析药剂质量分数、压力、前真空时间及加压时间对防腐处理效果的影响,比较处理前后对竹材力学性能的影响。研究结果表明,药剂质量分数是影响竹材防腐处理效果的显著因子;经铜唑防腐处理后,竹材的弹性模量(MOE)、顺纹抗拉强度和抗压强度无显著变化,抗弯强度(MOR)稍有降低。     

Effect of outdoor exposure on some properties of resin-treated plybamboo

The objective of this investigation was to evaluate some of the physical and mechanical properties of resin-treated plywood type panels manufactured from bamboo strips (Gigantochloa scortechinii). Experimental plybamboo samples were made from low molecular weight phenol formaldehyde (LMwPF) treated bamboo strips. They were exposed to outdoor condition ranging from 1 to 12 months. Modulus of elasticity (MOE), modulus of rupture (MOR), compression strength, and surface roughness of treated and untreated samples were evaluated. Resin impregnated samples had the highest bending and compression strength properties. While the untreated samples failed after 3-month of outdoor exposure. Treated specimens exposed for 12-month had the MOE, MOR, and compression strength values of 14,253 N/mm², 101.3 N/mm², and 34.63 N/mm², respectively. Surface quality of both treated and untreated samples was adversely influenced as the function of outdoor exposure time, based on numerical values obtained from a stylus type equipment. Overall properties of treated samples tested in work resulted in higher values than those of untreated samples. It appears that resin impregnation could be considered as an alternative method to enhance the characteristics of plybamboo exposed to environmental conditions as can be concluded from the results of this study.     

Effects of cross-linking on mechanical and physical properties of agricultural residues/recycled thermoplastics composites

Maleated graft polyolefins as cross-linking agents (CAs) are widely used to improve properties of wood thermoplastic composites made by melt extrusion process. In this study, novel CAs, free isocyanate group (NCO)-terminated urethane pre-polymers (UPs) were synthesized and used in manufacturing wheat straw (WS)/recycled polyethylene (PE) composites. The composites using polymeric diphenylmethane diisocyanate (pMDI) as a CA were also made in comparison. The relationship between composite properties and the level of CA and its content as well as the composite density and hot pressing time were investigated based on wood based board processes. The results show that the internal bonding (IB) strength, the IB after soaked in boiling water for 2 h (2hWIB), the modulus of rupture (MOR), the modulus of elasticity (MOE) and the 24 h thickness of swell after absorption of water (24hTS) of the composites are significantly improved with increased CA contents and composite densities. The optimal hot pressing time is 1.1 min/mm at 180°C. The cross-linking function is attributed to the reaction between free NCOs of CA molecules with hydroxyls of WS and the moisture in the raw materials, as well as the interaction between weak polar chain segments in the CA molecules to the non-polar PE. It is highly feasible to manufacture high quality composite using WS and recycled PE as raw materials when cross-linked with just 2.5% of UPs.     

Incombustibility,physico-mechanical properties and TVOC emission behavior of the gypsum–rice husk boards for wall and ceiling materials for construction

Rice husk is a by-product of rice milling process, and a great resource as a raw biomass material for manufacturing value-added composite products. One of the potential applications is to use rice husk as filler for manufacturing gypsum–rice husk boards for wall and ceiling materials for construction. We investigated the effect of rice husk, addition on selected physico-mechanical properties, total volatile organic compound (TVOC), and incombustibility, on the gypsum board. With increasing rice husk contents, water and moisture absorption was decreased. Because of the replacement of pore between gypsum particles by rice husk, the moisture absorption was decreased as rice husk adding contents. By rice husk adding, MOR of the gypsum–rice husk boards were increased up to 9.8 MPa at 30 wt%. However, MOR was decreased more than 40 wt% of adding contents. The modulus of elasticity (MOE) showed similar behavior with MOR. However, internal bonding strength (IB) was slightly increased as rice husk adding contents up to 20 wt%, 0.5 MPa and decreased over 20 wt%. The incombustibility of the gypsum–rice husk boards decreased on increasing the rice husk adding content. However, up to 30 wt% of rice husk adding contents board samples was of incombustibility first class. Gypsum particle can be replaced up to 30 wt% by rice husk with incombustibility first class for housing materials. In all cases, TVOC emission factor and formaldehyde emission remained under the ‘Excellent’ grade as defined by Korean Air Clean Association (KACA).     

Effect of γ (Gamma)-radiation on the physico-mechanical properties of grafted jute fabric reinforced polypropylene (PP) composites

The bleached jute fabric (BJF) reinforced polypropylene (PP) composites with various contents of acrylic acid (AA)-treated BJF and un-AA-treated BJF were fabricated by compression moulding method at 190 °C. The AA-grafted BJF reinforced PP composites were then irradiated by γ-ray at various doses. The mechanical properties of neat PP (N-P), ungrafted-BJF and PP composites (UG-BJFPC), AA-grafted-BJF and PP composites (AA-BJFPC) and γ-ray cum AA-grafted-BJF and PP composites (γAA-BJFPC) show maximum tensile strength (TS) of 30, 46, 47 and 51 MPa, maximum flexural strength (FS) of 34, 49, 50 and 54 MPa and maximum Young’s modulus (E) of 280, 428, 436, and 680 MPa, respectively. The increase of TS, FS and E from UG-BJFPC are 2 %, 2 %, and 2 % for AA-BJFPC and 11 %, 10 % and 59 % for γAA-BJFPC. The TS, FS and E are found to increase with radiation dose up to 500Krad and then decrease. The water absorption (WA) for UG-BJFPC, AA-BJFPC and γAA-BJFPC is respectively about 14, 10 and 9 %, indicating a gradual development of hydrophobic character of the composites first by AA-treatment and then by γ-ray-treatment. AA treatment on jute fabric and gamma irradiation on composite result in significant change of morphology of the jute fabric composites surface and better mechanical bonding between fabric and polymer matrix, as a result improved mechanical properties are found.     

Assessment of the mechanical properties of nanoclays enhanced low Tg epoxy resins

The mechanical properties of the nanocomposites are dependent, not only of the clays content but, also, of the resin type and manufacturing process. In this context, the present study intends to develop a systematic study involving a low glass transition temperature (T_g) and low permeability epoxy resin (SR 1500 and the hardener SD 2503) with a commercially Nanomer I30 E nanoclays. Two dispersion processes were compared (direct (DM) and indirect method (IDM)) in terms of mechanical properties, as well as the influence of nanoclay content and hydro aging effect. It was possible to observe that the composites obtained by the indirect method present lower mechanical properties than the neat resin because there is residual acetone. For DM composites the tensile strength, fracture toughness and the specific energy absorbed by impact decreases with the reinforcement content, caused by particle agglomerates. Elastic modulus, at 25 °C, increases significantly and T_g increases slightly with the addition of nanoclays. Hydro aging promotes a progressive decreasing of the tensile strength and fracture toughness, with the clay content, reaching about 15 % and 7 %, respectively, for 6 wt% of nanoclays. On the other hand, a small increasing on specific energy absorbed was observed.     

Effects of husk particle size and calcium chloride on strength and sorption properties of coconut husk–cement composites

Coconut husks, residues generated during coconut processing, are available in abundant quantities in many parts of the tropics but are often treated as a waste material. This study investigated the effects of particle size and calcium chloride (CaCl₂) on strength and sorption properties of cement-bonded composites produced from coconut (Cocos nucifera) husk. Particle size, CaCl₂ and the interaction of both variables had significant effects (p < 0.05) on the density and the Modulus of Elasticity (MOE), while only particle size had significant effects (p < 0.05) on the Modulus of Rupture (MOR) of the composites. MOE, MOR, Water Absorption and Thickness Swelling (at 24 h) compare favourably with values reported for cement-bonded composites produced from similar lignocellulosics. These properties can be exploited in many applications where lightweight concretes are required.     

Preparation and characterization of glass fiber-coir hybrid composites by a novel and facile Prepreg/Press process

The present study explored the preparation of glass fiber-coir reinforced unsaturated polyester resin hybrid (GCU) composites with a novel Prepreg/Press fabrication process. Flexural, impact and thermal-mechanical properties of GCU composites were investigated. Coir reinforced unsaturated polyester resin (CU) composites was also prepared with the same process to explore the enhancement effect of glass fabric on the mechanical properties of coir-based composites. The effect of fabrication pressure on the mechanical properties of CU and GCU composites was examined. Micromorphology and interfacial reaction of the composites were analyzed. It is shown that GCU composites fabricated with the Prepreg/Press process have excellent flexural strength (185.0 MPa), MOE (18.3 GPa), and impact strength (67.2 kJ/m²). The mechanical properties of GCU composites increased with the increase of applied pressure up to 0.8 MPa in the Prepreg/Press process. However, further increase of applied pressure led to the decrease in mechanical properties. The addition of glass fabrics to GCU composites showed 419 % improvement in flexural strength, 708 % improvement in MOE and 562 % improvement in impact strength over coir-based composites. The micromorphology study proved that the poor interfacial bonding between coir and matrix led to the low mechanical properties of coir-based composites.     

Structural,thermal, and mechanical properties of polyurethane foams prepared with starch as the main component of polyols

In this study, rigid polyurethane foams were prepared using starch as the main component of polyols and their structural, thermal, and mechanical properties were investigated. The starch content in polyols was 30∼50 wt.%. The prepared polyurethane foams had a cell structure. When the starch content and -NCO/-OH molar ratio (TS4-05, TS3-07, and TS3-05) was low, polyurethane foams were not formed. To confirm the formation of a urethane linkage between -OH of the starch and -NCO of the 2,4-TDI, FT-IR spectroscopic analysis was performed. The thermal properties of polyurethane foams were analyzed by DSC and TGA. DSC thermograms showed two endothermic peaks: a sharp peak at a lower temperature and a broad peak at a higher temperature. Both peaks were shifted to higher temperature with starch content in polyols and -NCO/-OH molar ratio. Thermal degradation of polyurethane foams began at a lower temperature and ended at a higher temperature than that of starch. The impact resistance, compressive stress and modulus of polyurethane foams increased with -NCO/-OH molar ratio and starch content.     

Effect of coir fiber content and compatibilizer on the properties of unidirectional coir fiber/polypropylene composites

The main objective of this research was to study the effect of fiber content variation and stearic acid (SA) treatment on the fundamental properties of unidirectional coir fiber (CF) reinforced polypropylene (PP) composites. Several percentages of filler contents were used (10–40 wt %) in order to gain insights into the effect of filler content on the properties of the composites. Coir/PP composites were fabricated by compression molding, and the properties of composites were studied by physico-mechanical and thermal properties. The results from mechanical properties such as tensile strength (TS), tensile modulus (TM) and impact strength (IS) of the CF/PP composites were found to be increased with increasing fiber content, reached an optimum and thereafter decreased with further increase in fiber content. Treatment of the coir with SA as the coupling agent enhanced the mechanical properties, crystallization temperature and crystallinity of virgin PP and water desorption of the resulting composites, resulting from the improved adhesion between the CF and PP matrix. Scanning electron micrographs (SEM) of the tensile fractured samples showed improved adhesion between fiber and matrix upon treatment with SA. Interfacial shear strength (IFSS) of the composites was measured by single fiber fragmentation test (SFFT).     

Effect of curing time on physical and mechanical properties of phenolic-treated bamboo strips

Effect of pressing time on physical and mechanical properties of phenolic-impregnated bamboo strips was evaluated. Bamboo strips (Gigantochloa scortechinii) were impregnated with low molecular weight phenol formaldehyde (LMwPF) resin. Samples were submerged in LMwPF resin using a vacuum chamber of 750 mmHg for 1 h before it was released within 1.5 h. Treated strips were dried in an oven with a temperature of 60 °C within 6–9 h. It was hot pressed at 14 kg m^?2 and a temperature of 140 °C for 5, 8, 11, 14 and 17 min. The physical and mechanical properties of the test indicated that the properties of phenolic-treated strips have significantly increased as compared to control samples. Dimensional stability (water absorption, thickness swelling and linear expansion) of the phenolic-treated properties were significantly lower than control after 5-min pressing time. The antishrink efficiency (ASE) of phenolic-treated strips increased when pressing time were extended from 5 to 17 min. The mean value of modulus of rupture (MOR) for the control samples (177 N mm^?2) showed a significant difference with phenolic-treated strips after 17-min pressing time (224 N mm^?2). However, there is no significant difference in compression parallel to grain. The MOE of phenolic-treated strips was 21,777 N mm^?2 and for control was 18,249 N mm^?2, whereas the compression parallel to grain values for phenolic-treated and control samples were 94 and at 77 N mm^?2, respectively.     

Mechanical properties of flax-g-poly(methyl acrylate) reinforced phenolic composites

In order to develop composites with better mechanical properties and environmental performance, it becomes necessary to increase the hydrophobicity of the natural fibers and to improve the interface between matrix and natural fibers. Graft copolymerization of natural fibers is one of the best methods to attain these improvements. Only few workers have reported the use of graft copolymers as reinforcing material in the preparation of composites. So in the present paper, we report the preparation of graft copolymers of flax fibers with methyl acrylate (MA) using Fenton’s reagent (FAS-H₂O₂) as redox system. Synthesized flax-g-poly(MA) was characterized with FTIR, TGA/DTA, scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. Composites were prepared using flax-g-poly(MA) as a reinforcement and phenolformaldehyde (PF) as the binding material. Mechanical properties of phenol-formaldehyde composites were compared and it has been found that composites reinforced with flax-g-poly(MA) showed improvement in mechanical properties. Composites reinforced with flax-g-poly(MA) showed better tensile strength (235 N) and compressive strength (814 N) in comparison to composites reinforced with original flax fiber which showed lesser tensile strength (162 N) and compressive strength (372 N). Composites reinforced with flax-g-poly(MA) shows the improved MOR, MOE, and SP.     

Thermal and mechanical properties of environment-friendly ‘green’ plastics from stearic acid modified-soy protein isolate

Most plastics, at present, are petroleum-based and do not degrade over many decades under normal environmental conditions. As a result, efforts towards developing environment-friendly and biodegradable ‘green’ plastics for various commercial applications have gained significant momentum in recent years. Soy protein isolate (SPI)-based ‘green’ plastics have been shown to suffer from high moisture sensitivity and low strength. These properties have limited their use in most commercial applications. They are also difficult to process into sheets without any plasticizer. The commonly used plasticizer, glycerol, tends to leach out over time producing time-dependent properties, which is highly undesirable for commercial applications. The objectives of the current research are to reduce the moisture sensitivity and simultaneously improve the tensile properties of SPI by incorporation of stearic acid without affecting its biodegradability. The effect of stearic acid and glycerol on the tensile and thermal properties of SPI has been characterized using various techniques to determine the interaction mechanisms between stearic acid and soy protein. Mechanical properties were characterized using Instron tensile tester. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA) and X-ray diffraction (XRD) techniques have been used to determine the effects of stearic acid and glycerol on the surface chemistry, thermal transitions and thermal degradation of the stearic acid modified SPI plastic (resin). The tensile test results show that Young’s modulus increased on increasing the stearic acid content, reaching the maximum value at about 25% (by weight of SPI powder) stearic acid. Further increase in stearic acid content from 25 to 30% led to a reduction in Young’s modulus. The moisture content, fracture stress, strain, and energy at break decreased steadily on increasing the stearic acid from 0 to 30% for SPI containing 30% glycerol. At 25% stearic acid content, the modulus and the fracture stress increased significantly, whereas the fracture strain, energy at break and the moisture content decreased on reducing glycerol content. Scanning electron microscopy photomicrographs of fractured surfaces showed a layered structure for stearic acid modified-SPI resin. TGA measurements showed that the thermal degradation of stearic acid modified-SPI resin initiated at higher temperature than the SPI resin. DSC scans indicated that stearic acid modified-SPI resin had a small degree of crystallinity, which was confirmed by X-ray diffraction patterns. Modifying SPI resin with stearic acid has been successful in obtaining better tensile and thermal properties as well as reduced moisture sensitivity without any processing problems.     

Flame retardancy,Thermal and mechanical properties of Kenaf fiber reinforced Unsaturated polyester/Phenolic composite

Unsaturated polyester (UP) resin has been blended with phenolic resin (PF) resole type at various ratios to obtain a homogeneous blend with improved flame resistance compared to its parent polymers. The polymer blend was reinforced with 20 wt% kenaf using hand lay out technique. Fourier transform infrared spectroscopy (FT-IR) was used to characterize changes in the chemical structure of the synthesized composites. The thermal properties of the composites were investigated using thermogravimetric analysis (TGA). The thermal stability of UP/PF kenaf composites co-varies with the PF content, as shown by the degradation temperature at 50 % weight loss. The char yield of the composites increases linearly with PF content as shown by the TGA results. The flammability properties of the composites were determined using the limiting oxygen index (LOI) and UL-94 fire tests. The LOI increased with the PF content while the composites exhibit improved flame retardancy as demonstrated by UL-94 test. The mechanical and morphological properties of the composites were determined by tensile test and scanning electron microscopy (SEM), respectively. The tensile strength and the Young’s modulus of the blend/composites slightly decreased with increasing PF content albeit higher than PF/kenaf fiber composites.