Biosynthesis of polyhydroxyalkanoates using <Emphasis Type="Italic">Cupriavidus necator</Emphasis> H16 and its application for particleboard production

Different concentrations of palm oil and urea were used in a preliminary experiment conducted in a shake-flask to determine the optimum conditions for the biosynthesis of polyhydroxyalkanoates (PHA). The best concentration was found to be 10 g/L palm oil and 0.54 g/L urea which produced the highest concentration of PHA (8.11 g/L). A 13 L bioreactor was employed using a fed-batch fermentation with the derived optimum conditions and yielded a PHA concentration of 97 g/L. The melting temperature and thermal degradation temperature of PHA were determined to be 173 °C and 254 °C, respectively. The PHA was applied as a binder to make particleboard from para-rubber-wood flakes which were pretreated with microwaves and steam before being mixed with PHA, and control panels were also manufactured from un-pretreated flakes and without the addition of PHA. The mechanical and physical properties of the panels were determined including the modulus of rupture (MOR), internal bond strength (IB), water absorption, and thickness swelling according to the Japanese Industrial Standard for particleboard (JIS A 5908, 2003). The result showed that none of the panels produced met all the minimum requirements for Type 8 Particleboard of Japanese Industrial Standard JIS A 5908. The MOR of the control panel passed the JIS A 5908 standard for MOR (> 8.00 MPa) but did not meet the IB requirement (>0.15 MPa). The addition of PHA as a binder in proportions of 15, 20 and 30 wt% in the control panel enhanced the IB to 0.18, 0.19. 0.22 MPa, respectively. However none of the other parameters of these boards met the relevant JIS A 5908 standard. The pretreatment process was also unable to enhance the properties of the particleboard but that using PHA as a binder instead of urea formaldehyde was able to meet the relevant internal bonding standard for particleboard manufactured from para-rubber-wood flakes which are a waste product in the furniture industry.     

Effect of steam on bonding strength and dimensional stability of laminated veneer lumbers manufactured using different adhesives

Laminated veneer lumbers (LVLs) manufactured from wood with different adhesives are being increasingly used in the construction of furniture frames and buildings. Yet there is little information available concerning the dimensional stability and shear strength of LVLs after being exposed to steam. In this study, LVLs were manufactured from poplar and beech veneers with phenol/formaldehyde (PF), poly(vinyl acetate) (PVAc), Desmodur-VTKA (D-VTKA) and urea/formaldehyde (UF) adhesives. Dimensional stability of LVLs was measured after being exposed to steam for 2, 6, 12, 24, 48 and 96 h, according to the Turkish Standard (TS) 3639, and also shear strength was measured (according to BS EN 205). The highest initial density of 0.93 g/cm³ was for beech LVL with VTKA adhesive. After exposure to steam for 96 h, the highest weight increase of 65.7% was for poplar LVL with PVAc, the highest radial swelling of 5.7% was for beech LVL with UF, the highest tangential swelling of 7.9% was for beech LVL with PF and the highest longitudinal swelling of 0.5% was for beech LVL with VTKA. The highest shear strength value of 15.8 N/mm² among all samples without exposure to steam was obtained for beech LVL with PVAc adhesive and the lowest shear strength was obtained as 4.48 N/mm² for poplar LVL with UF adhesive.     

Low formaldehyde emission particleboard panels realized through a new acrylic binder

The effectiveness of acrylic resins as low formaldehyde emission binders for particleboard production was explored. In particular, a multifunctional methacrylic monomer, ethoxylated bisphenol A dimethacrylate, classified as nonskin and eyes irritant, was selected and tested. In comparison panels realized with classic urea‐formaldehyde (UF) binder were also prepared. No significant differences were found through the morpholocigal analysis of samples prepared with the two different binders. Moreover, particleboard panels realized with the acrylic binder showed better mechanical properties and lower water absorption and thickness swelling in comparison with corresponding panels realized with the UF binders. Furthermore, the replacement of the UF with the acrylic binder did not affect thermal insulation properties of the panels. Formaldehyde release tests revealed that particleboard panels obtained by applying the acrylic binder can be classified as E1 following the European classification and even F**** following the stricter Japanese classification. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of temperature on hygroscopic thickness swelling rate of composites from lignocellolusic fillers and HDPE

Effect of temperature on hygroscopic thickness swelling rate of lignocellolusic fillers/HDPE (high density polyethylene) composites was investigated. The composites were manufactured using a dry blend/hot press method. In this method, powder of plastic and dried powder of lignocellolusic material were mixed in high‐speed mixer and then the mixed powder were pressed at 190°C. Lignocellolusic fillers/HDPE composites panels were made from virgin and recycled HDPE (as plastic) and wood sawdust and flour of rice hull (as filler) at 60% by weight filler loadings. Nominal density and dimensions of the panels were 1 g/cm³ and 35 × 35 × 1 cm³, respectively. Thickness swelling rate of manufactured wood plastic composites (WPCs) were evaluated by immersing them in water at 20, 40, and 60°C for reaching a certain value where no more thickness was swelled. A swelling model developed by Shi and Gardner [Compos. A, 37 , 1276 (2006)] was used to study the thickness swelling process of WPCs, from which the parameter, swelling rate parameter, can be used to quantify the swelling rate. The results indicated that temperature has a significant effect on the swelling rate. The swelling rate increased as the temperature increased. The swelling model provided a good predictor of the hygroscopic swelling process of WPCs immersed in water at various temperatures. From the activation energy values calculated from the Arrhenius plots, the temperature had less effect on the thickness swelling rate for the composites including wood sawdust compared with the rice hull as filler and the composites including recycled compared with the virgin HDPE as plastic. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Influence of Process Variables on the Bending Strength of Particleboard Produced from Arabian Date Palm Mid-Rib Chips

Feed produced from Arabian date palm (Phoenix dectylifera-L) biomass and impregnated with urea formaldehyde (UF) adhesive binder is subjected to hot compaction to yield particleboard panels of excellent bending strength. Process variables such as press temperature, press cycle time, compaction pressure and particle thickness are shown to exercise significant effects on the bending strength of the final product. The influence of chipping technique on particle integrity and surface quality is highlighted. Scanning electron microscopic (SEM) evidence is presented to illustrate microstructural damages caused by excessively high compaction pressure.     

New measurement of particle size distribution by a buoyancy weighing-bar method

The rates which particles from JIS Test Powders 1, Class 2 (silica sand), Class 3 (silica sand), Class 16 (calcium carbonate, heavy), and JIS Test Powder 2, Class GBM-20 (barium titanate glass) settled out of homogenous suspensions were determined using the principles of the buoyancy weighing-bar method as well as a sedimentation balance. Samples were standardized by Japanese Industrial Standard, and the dispersing agent was NaPP or NaHMP, while the viscosity improver was a starch syrup solution. Although constructing a handmade sedimentation balance is difficult, developing a handmade weighing tool capable of measuring particle size distribution is easy. Herein three weighing-bars, which were composed of aluminum, stainless steel, and copper, were used to measure the particle size distribution. However, an aluminum slit-cylinder occasionally replaced the weighing-bars. The weighing data obtained via an analytical balance were controlled by connecting the balance to a personal computer with an RS-232C interface, and the determined particle size agreed well with the data obtained by Andreasen analyses and the sedimentation balance.     

Adhesive and curing properties of chicken feather/blood-based adhesives for the fabrication of medium-density fiberboards

This study was conducted to investigate the adhesive properties of chicken feather (CF)-based adhesives for wood-based panels. CF was hydrolysed in sodium hydroxide solutions of 5%, 7.5% and 10% (CF-AK). Chicken blood (CB) hydrolysed in sulfuric acid solution of 5% (CB-AC) was used as a hardener. The adhesives were formulated by crosslinking 60% CF-AK, 10% CB-AC and 30% formaldehyde-based crosslinking agents (formalin, melamine-urea-formaldehyde and phenol-formaldehyde prepolymers) on a solid weight basis. The CF-based adhesives were very viscous at room temperature, but the viscosity at 50 °C ranged from 300 to 600 mPa·s resulting in a sprayable adhesive. From the DSC analysis, the use of CF-AK-10% in the CF-based adhesives need longer curing time compared with that of CF-AK-5%. Most mechanical strength properties and dimensional stability of MDF bonded with CF-based adhesives were similar to those of commercial urea-formaldehyde (UF) resin. However, internal bonding strength of most MDF bonded with CF-based adhesives was higher than that with the UF resin. Most adhesive properties of the MDF manufactured with the new CF adhesive met the Korean Standard requirements for interior MDF. These results suggest that CF and/or CB can be used as raw materials for environment-friendly adhesives for producing wood panels.     

Physical Properties of Particleboard Panels Manufactured from Phoenix Dactylifera-L (Date Palm) Mid-rib Chips using Ureaformaldehyde Binder

Pertinent physical properties of experimental particleboard specimens produced from date palm (Phoenix dactylifera-L) branch mid-ribs chips impregnated with ureaformaldehyde (UF) polymer binder are investigated. The effect of process variables (press temperature, pressure, press cycle time and particle thickness) on thickness swelling, water absorption, equilibrium moisture content (EMC) and panel density are presented graphically and discussed in terms of process variables, internal structure of particles and UF-aqueous environment interactions. Scanning electron microscopy (SEM) data on the internal structure of date palm branch mid-ribs are also reported.     

Preparation and properties of chemical cellulose from ascidian tunic and their regenerated cellulose fibers

Chemical cellulose (dissolving pulp) was prepared from ascidian tunic by modified paper‐pulp process (prehydrolysis with acidic aqueous solution of H₂SO₄, digestion with alkali aqueous solution of NaOH/Na₂S, bleaching with aqueous NaOCl solution, and washing with acetone/water). The α‐ cellulose content and the degree of polymerization (DPw) of the chemical cellulose was about 98 wt % and 918, respectively. The Japanese Industrial Standard (JIS) whiteness of the chemical cellulose was about 98%. From the X‐ray diffraction patterns and ¹³C‐NMR spectrum, it was found that the chemical cellulose obtained here has cellulose Iβ crystal structure. A new regenerated cellulose fiber was prepared from the chemical cellulose by dry–wet spinning using N‐methylmorpholine‐ N‐oxide (NMMO)/water (87/13 wt %) as solvent. The new regenerated cellulose fiber prepared in this study has a higher ratio of wet‐to‐dry strength (<0.97) than commercially regenerated cellulose fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1634–1643, 2002.     

Phenol–urea–formaldehyde resin co-polymer synthesis and its influence on Elaeis palm trunk plywood mechanical performance evaluated by 13C NMR and MALDI-TOF mass spectrometry

This study evaluated a new method of producing phenol–urea–formaldehyde (PUF) adhesives formulated differently under actual “in-situ” resin synthesis conditions. This was carried out by co-polymerizing urea formaldehyde (UF) resin with phenol–formaldehyde resin in the core layer of low molecular weight (LMW) phenol–formaldehyde (PF) resin treated Elaeis palm trunk veneers during the gluing process of Elaeis palm plywood. Matrix assisted laser desorption Ionization time of flight (MALDI-TOF) mass spectrometry (MS) illustrated and confirmed a series number of the phenol–urea co-condensates repeating unit in the prepared PUF resins which corroborated well with its mechanical properties (modulus of elasticity and modulus of rupture), bonding quality (dry test and weather boil proof or WBP test) and physical properties. A series of PF, UF and PUF resins oligomers forming repeating units up to 1833 Da were identified. Besides that, the solid state ¹³Carbon nuclear magnetic resonance (NMR) interpretation identified that the signal at 44–45 ppm and 54–55 ppm corresponding to methylene bridges were co-condensated in between phenol and urea in the PUF resin system. The ¹³C NMR investigation showed that the synthesis process of PUF resin contained no free formaldehyde elements. Furthermore, the proportion of urea and methylolureas in the mixture to synthesis PUF resin were sufficient and incorporated well into the formulation by reacting with LMWPF units to form co-condensed methylene bridges. This study showed a new and useful method to synthesize PUF resin during the gluing process of manufactured Elaeis palm plywood which can also enhance the performance of Elaeis palm plywood panels for structural instead of utility grade applications.     

Reduction of Formaldehyde Emission from Particleboard by Phenolated Kraft Lignin

The aim of this study was the reduction of formaldehyde emission from particleboard by phenolated Kraft lignin. For this purpose, the lignin was extracted from black liquor and then modified by phenolation. During the urea formaldehyde (UF) resin synthesis different proportions of unmodified and phenolated Kraft lignins (10%, 15%, and 20%) were added at pH = 7 instead of the second urea. Physicochemical properties and structural changes of resins so prepared, as well as the internal bond (IB) strength and formaldehyde emission associated with the panels bonded with them were measured according to standard methods. The Fourier transform infrared (FTIR) analysis of lignin indicated that the content of O–H bonds increased in phenolated lignin while the aliphatic ethers C–O bonds decreased markedly in the modified lignin. Since both synthesis of UF resins and lignin phenolation are carried out under acid conditions, phenolation is an interesting way of modifying lignin for use in wood adhesive. The panels bonded with these resins showed significantly lower formaldehyde emission compared to commercial UF adhesives. The UF resin with 20% phenolated lignin exhibited less formaldehyde release without significant differences in internal bond strength and physicochemical properties compared to an unmodified UF resin. XRD analysis results indicated that addition of phenolated lignin decreased the crystallinity of the hardened UF resins.     

Urea impregnated multiwalled carbon nanotubes; a formaldehyde scavenger for urea formaldehyde adhesives and medium density fiberboards bonded with them

Multiwalled carbon nanotubes (MWCNTs) were subjected to modification by urea to use as formaldehyde scavenger in urea formaldehyde (UF) adhesive and reducing the free formaldehyde emission of the medium density fiberboards (MDFs). Morphological differences besides elemental analysis was investigated using field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy. The effect of urea impregnated MWCNTs filler on the physical, morphological and thermal properties of the UF resin has investigated. Furthermore, characterization of the mechanical properties, free formaldehyde emission and thickness swelling were carried out for the MDF panels. From the results, the free formaldehyde of the UF resins was significantly decreased. The lowest free formaldehyde was belonged to the sample with 3 wt% of scavenger which was about 71% lower than the value for neat UF resin. Accordingly, the formaldehyde emission of the fiberboards was also showed a descending trend by incorporation of MWCNTs-U to the composite structure. It was decreased from 9.67 to 3.89 mg/100 g dried board. These results indicated that the prepared nano modifier was successfully performed as a formaldehyde scavenger for the UF resin and could prevent the hazards of the free formaldehyde emission from MDF panels.     

The effect of soda bagasse lignin modified by ionic liquids on properties of the urea–formaldehyde resin as a wood adhesive

The aim of this research was to investigate the influence of lignin modified by ionic liquids on physical and mechanical properties of plywood panels bonded with the urea–formaldehyde (UF) resin. For this purpose, soda bagasse lignin was modified by the 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) ionic liquid and then the various contents of unmodified and modified lignins (10, 15, and 20%) were added at pH=7 instead of second urea during the UF resin synthesis. The physicochemical properties of the prepared resins as well as the water absorption, shear strength, and formaldehyde emission of the plywood panels made with these adhesives were measured according to standard methods. According to Fourier Transform Infrared (FTIR) Spectrometry, by treatment of lignin, the C=O, C–C, and C–H bonds decrease while the content of the C–N bond dramatically increases. Based on the finding of this research, the performance of soda bagasse lignin in UF resins dramatically improves by modification by ILs; as the resins with modified lignin yielded lower formaldehyde emission and water absorption when compared to those made from unmodified lignin and commercial UF adhesives, respectively. The shear strength as well as wood failure percentages are lower for the panels produced with modified lignin than for the panels produced with UF resins alone.     

Enhancement of Dimensional Stability of Biocomposites Containing Agricultural Waste by Heat-Treatment Method

The objective of this research was to enhance the dimensional stability of biocomposites containing agricultural waste using a heat-treatment method. For this aim, cotton stalk (CS) flour was treated at 150 or 180°C for 30 or 60 min in atmospheric air. The ratio of softwood fiber to heat-treated (CS) flour in the biocomposites (medium-density fiberboards, MDF) with a density of 700 kg/m³ was 75/25%. The MDF panels were made using standardized procedures that simulated industrial production at the laboratory. Heat treatment of the CS flour significantly enhanced the water resistance of the MDF panels such as thickness swelling and water absorption. An increase to 60 min of heat treatment at 150 or 180°C resulted in a further reduction of the swelling properties compared to the standard treatment (30 min). However, the mechanical properties such as modulus of rupture, modulus of elasticity, and internal bond strength declined as the temperature and time increased. This study revealed that the dimensional stability of the MDF panels incorporated with heat-treated CS flour was better than that of the panels incorporated with untreated CS flour.     

Urea–formaldehyde–propionaldehyde physical gelation resins for improved swelling in water

Urea–formaldehyde (UF) resins' water tolerance and swelling thickness of interior‐grade wood panels bonded with UF resins were improved markedly by introducing small amounts of UFPropanal (UFP) polycondensates into the UF resin. ¹³C NMR of urea–propanal (UP) resins showed that urea and propanal do react up to the formation of dimers. The water repellancy imparted by insertion in the resin of the alkyl chain of propanal limits the proportion of propanal that can be used. Gel permeation chromatography showed that this appears to be so because UP resins and UFP resins exist as an equilibrium between two separate intermingling phases, namely one in solution and the second in a state of physical gelation. This latter is different from the state of physical gelation observed on ageing or advancement of formaldehyde‐only based polycondensation resins. This physical gelation is brought on by the insertion in the resin of the water repellant chain of the propanal reacted with urea and constitutes a new state of physical gelation of polycondensates other than what was already reported in the literature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5131–5136, 2006     

淀粉与脲醛树脂复合胶粘剂的制备与性能研究

以聚乙烯醇(PVA)、硼砂、玉米淀粉、次氯酸钠、亚硫酸钠和纳米高岭土等为主要原料,制备淀粉胶粘剂;然后以常温固化的UF(脲醛树脂)作为淀粉胶粘剂的交联改性剂,制备UF/淀粉复合胶粘剂。研究结果表明:当w(PVA)=10%、m(硼砂)∶m(干淀粉)=12.5∶30、w(纳米高岭土)=2%和m(淀粉胶)∶m(UF胶)=5∶5时,相应复合胶粘剂的综合性能(包括流动性、耐水性和干湿胶接强度)相对最佳。     

Effects of Adding Unsaturated Polyester to the PVAC Adhesive on the Dimensional Stability of Laminated Veneer Lumber

Many properties of wood are affected by changes in moisture content below the fiber saturation point of wood. In this study, the dimensional stability of laminated veneer lumber (LVL), according to TSI EN 4084 and EN 4086, was evaluated. For this purpose Scots pine (Pinus sylvestris L.) and Oriental beech (Fagus orientalis L.) LVL panels were used. Panels of LVL were manufactured from cut veneers, and poly-vinyl acetate (PVAc), unsaturated polyester (uPE) and mixtures of them, as adhesives. Laminated veneer lumber panels with 4 plies and 5 mm in thickness were produced for each group. Depending on the adhesive type, the swelling and water absorption of the samples were measured by determining the weight increase in the two conditions of oven dried and being above the fiber saturation point. The lowest volumetric swelling of the Scots pine was measured as 10.4% bonded with 100% PVAc (control) and the highest volumetric swelling was measured as 13.8% bonded with 90% PVAc and 10% unsaturated polyester. The lowest volumetric swelling of the Oriental beech was measured as 17.2% bonded with 100% PVAc (control) and the highest volumetric swelling was found to be 21.8% bonded with 90% PVAc and 10% unsaturated polyester. Statistical analysis results show that adding unsaturated polyester to the PVAc increased the volumetric swelling and water absorption levels of both the Scots pine and Oriental beech LVL panels.     

A comparison between lignin modified by ionic liquids and glyoxalated lignin as modifiers of urea-formaldehyde resin

The aim of this research was to compare the influence of modified lignin by ionic liquid (IL) on the physical and mechanical properties of wood-based panels bonded with urea-formaldehyde (UF) resin with the effect of glyoxalated lignin (GL) on UF properties. For this purpose, soda bagasse lignin was respectively modified by 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) IL and glyoxal and then the various content of modified lignins (10, 15, and 20%) were added at pH=7 during the UF resin synthesis instead of the second urea . The changes in the structure and thermal properties of lignin, after and before modification with glyoxal and IL, were analyzed by Fourier transform infrared spectrometry (FTIR) and differential scanning calorimetry (DSC). The physicochemical properties of the prepared resins as well as the water absorption, shear strength, and formaldehyde emission of the plywood panels made with these adhesives were measured according to standard methods. According to the FTIR spectra, the content of C=O bond increased in GL while in the IL-treated lignin the content of C–N bond markedly increased. DSC analysis indicated that lignin modified by IL had lower glass transition temperature (T_g) value compared to those modified with glyoxal and unmodified lignin, respectively. The UF resins containing IL-treated lignin exhibit a faster gel time compared to those prepared with GL. Equally, the plywood panels prepared with an IL had lower formaldehyde emission and higher mechanical strength compared to those made from UF resin containing GL. There were no significant differences in dimensional stability of the panels bonded with UFs modified with GL and those with IL-modified lignin.     

Influence of acrylamide copolymerization of urea–formaldehyde resin adhesives to their chemical structure and performance

To lower the formaldehyde emission of wood‐based composite panels bonded with urea–formaldehyde (UF) resin adhesive, this study investigated the influence of acrylamide copolymerization of UF resin adhesives to their chemical structure and performance such as formaldehyde emission, adhesion strength, and mechanical properties of plywood. The acrylamide‐copolymerized UF resin adhesives dramatically reduced the formaldehyde emission of plywood. The ¹³C‐NMR spectra indicated that the acrylamide has been copolymerized by reacting with either methylene glycol remained or methylol group of UF resin, which subsequently contributed in lowering the formaldehyde emission. In addition, an optimum level for the acrylamide for the copolymerization of UF resin adhesives was determined as 1%, when the formaldehyde emission and adhesion strength of plywood were taken into consideration. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Microfibrillated-cellulose-modified urea-formaldehyde adhesives with different F/U molar ratios for wood-based composites

The relationship between urea–formaldehyde (UF) adhesives (E0 and E1 classes) and microfibrillated-cellulose (MFC) and its effect on the mechanical properties of laminated veneer lumbers (LVLs) were investigated. Bending strength, modulus of elasticity in bending, and tensile shear strength of the LVLs were determined. The morphology, gel time, viscosity, and acidity of the modified UF adhesives were also investigated. The tensile shear strength of the LVLs significantly increased (2.89 to 3.35 N/mm²) as the MFC suspension was increased to 3.75 g in the 7.50 g E0 class UF adhesive, while it slightly increased (3.10 to 3.16 N/mm²) as the MFC suspension was increased to 2.5 g in the 8.75 g E1 class UF adhesive. The results showed that the bond performance of the E0 class adhesive with the MFC was better than that of the E1 class adhesive with the MFC. The MFC was found to be valuable nanoscale reinforcing filler for the improvement of bond performance of UF adhesive, in particular, E0 class adhesive, in the production of wood-based composites.