Volume 69, Issue 2

Commercial lignosulfonates (LS), recovered from bisulfite pulping processes, are known for their wide polydispersity. In this study, LS were fractionated by ultrafiltration (UF) and based on their solubility in ethanol (EtOH) solutions. The combination of both methods leads to a set of fractions of varying properties, suitable for several applications. UF gives well-separated fractions, with low polydispersity, and increasing functionality (sulfonate and phenolic hydroxyl groups) with decreasing molecular weight (MW). EtOH solubility yields more polydisperse fractions but still appears to be an easy and rapid way to obtain fractions with increasing MW. The residual sugars in LS, resulting from incomplete removal of hemicelluloses, were found to be mainly in the form of low MW oligomers, which were not bound chemically to lignin. Thermal degradation of the different fractions was also compared, giving better comprehension of the influence of the structure and composition. A glass transition temperature ( T g ) could be measured for some fractions and was correlated to their MW.

Precipitation and utilization of lignin from black liquor (BL) offers many promising advantages to modern kraft pulp mills. A novel process, known as “LignoBoost”, has recently been introduced as a process for separating lignin from BL; it results in lignins with a low ash and high dry solid content. There is a lack of knowledge regarding the influences of process parameters on the behavior of lignin in the precipitation step. In this study, the yield of precipitated lignin and its average molecular weight (MWt) and carbohydrate content were the focus. Nuclear magnetic resonance (NMR) analysis showed that the lignin yield increased at lower pH and temperatures or when the ion strength of BL was elevated. High yield lignins contained more low MWt components and such lignins have more phenolic OH and methoxy groups. Xylan content of the lignins decreased with decreasing pH and increasing temperature, but glucomannan content was virtually unaffected by the conditions of precipitation.

The Fenton reaction is supposed to play a key role in the initial wood degradation by brown rot fungi. Wood was modified with 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) and glutaraldehyde (GA) to various weight percentage gains in order to study if these types of modifications are able to reduce wood degradation by Fenton reagent. Veneers modified with higher concentrations (1.2 and 2.0 mol l -1 ) of both chemicals exhibited minor losses in mass and tensile strength during treatment with Fenton reagent, which shows restrained oxidative degradation by hydroxyl radicals. The decomposition rate of H 2 O 2 was lower in the Fenton solutions containing modified veneers than in those containing unmodified controls. More CO 2 evolved in systems containing unmodified veneers than in systems with modified veneers, indicating that modification protected wood from mineralisation. The reason for the enhanced resistance of modified wood to the Fenton reaction is attributed to impeded diffusion of the reagent into the cell wall rather than to inhibition of the Fenton reaction itself. The results show that wood modification with DMDHEU and GA is able to restrain the degradation of wood by the Fenton reaction and can explain why modified wood is more resistant to brown rot decay.

Eleutherococcus trifoliatus also known as the three-leaved Eleutherococcus , a member of the Araliaceae (ginseng) family, is commonly used in traditional Chinese medicine. Recently, many studies have demonstrated the bioactivities of the secondary metabolites in E. trifoliatus . In this study, a monoterpene synthase from E. trifoliatus has been characterized. A pair of degenerate primers was designed and a fragment with conserved region of terpene synthase (TPS) was obtained. After 5′- and 3′-rapid amplification of cDNA ends (RACE), the full-length cDNA was obtained. The gene designated EtLIM contains an open reading frame of 1752 bp with a predicated molecular mass of 67.3 kDa. It was expressed in young leaves, stems, and drupes. The product of EtLIM has been identified by gas chromatography/mass spectrometry (GC/MS) as limonene.

The known method of wood modification by epoxidized linseed oil (ELO) has a limiting practical application due to the rapid polymerization of ELO in the presence of acetic acid (AA) needed as a catalyst. The present study was designed to develop an alternative method by means of a two-step process to avoid the rapid polymerization. The treatment options were tested on Scots pine sapwood, with the dimensional stability (DS) of the treated samples in focus. The new method provided an anti-swelling efficiency (ASE) in the range of 40–57%, which was even better than the thermally modified (TM) reference samples with 40% ASE. The developed two-step process is a feasible and practical approach for ELO treatment of wood.

Scots pine samples were impregnated with epoxidized linseed oil (ELO) by means of a two-step process, and the effect of treatments has been studied concerning the Fourier transform infrared (FTIR) spectra, mechanical properties, moisture uptake, and field test performance. FTIR analysis of ELO-treated samples revealed that part of the ELO epoxy reactive group was chemically bound to the hydroxyl groups of wood. ELO-treated samples have improved dimensional stability, while the mechanical properties were slightly reduced and the moisture uptake was significantly lowered. The field performance of lap joints treated with ELO (90 kg m -3 ) after 60 months’ exposure showed great improvements in performance, as the average annual moisture content (MC) was maintained at the level of 19.3% compared to 34.6% for lap joints treated with linseed oil (LO). The lap-joint area was not stained, and less discoloration by staining fungi on the external surfaces was observed in ELO-treated samples compared to samples treated with LO.

The effects of two power levels (50 and 150 W) and five time levels (10, 20, 40, 60 and 120 s) of glow discharge in helium dielectric barrier discharge (He-DBD) has been investigated in the context of surface modification of medium density fiberboard (MDF) panels. He-DBD elevated the surface wettability of MDF panels as assessed by dynamic contact angle (CA) measurements including the determination of surface free energy, droplet volume and spreading contact area of droplets. The chemical changes of the MDF surfaces were also characterized by X-ray photoelectron spectroscopy (XPS). Expectedly, the apparent CA and droplet volume decreased with increasing power and time of glow discharge, mainly at the 150 W power level. The oxygen content of the surfaces, the surface free energy and the spreading contact area increased upon treatment. At higher energy levels the treatment time could be reduced, which is essential for future applications in industrial processes.

The radio frequency oxygen plasma (RF-OP) treatment of wood was in focus, namely the surface properties of poplar veneer has been analyzed as a function of RF-OP treatment power concerning the chemical composition, free radicals, morphology and roughness. In addition, the interfacial adhesion of plywood composites was measured by determining the shear strength. The results show that RF-OP treatment introduced free radicals and polar groups onto the veneer surface, changed the surface morphology, and increased the surface roughness. Shear strength of the composite was improved. It can be concluded that RF-OP treatment is most effective at the optimal treatment power of 200 W.

The effect of multiwalled carbon nanotubes (MWCNT) as reinforcement on the properties of urea-formaldehyde (UF) resin and medium-density fiberboards was investigated. MWCNT was added to UF in two concentrations, and the effects were studied by means of differential scanning calorimetry and dynamic mechanical thermal analysis in terms of the curing and viscoelastic properties of the resins. In the presence of MWCNT, the activation energy of the resins was lowered, and their storage modulus and thermal conductivity were enhanced. The formaldehyde emission decreased and mechanical properties increased after addition of MWCNT to UF resin.

Abstract: This study examines the swelling of TEMPO-oxidized nanofibrillated cellulose (NFC TEMPO , shortly NFC) on both the particle and interparticle levels. The sum of the intraparticle and interparticle swelling is referred to as the network swelling. A centrifugal method, based on a modification of the water retention value test, was used to measure the network swelling of NFC, a pigment, and some pulp fibers. It was found that the network swelling of NFC is highly dependent on its concentration within a fiber matrix. The particle swelling of NFC and pulp fibers was analyzed by differential scanning calorimetry (DSC) and solute exclusion. The counterion for the NFC varied among the Na + , H + , and Ca 2+ forms. The counterion has a very large effect on the particle and network swelling of NFC, with Ca 2+ giving the lowest swelling and Na + the highest swelling. An industrially feasible method for changing the counterion of NFC from the nominal Na + to the Ca 2+ form, and thus improving dewatering properties, is given.

The work aimed at the improvement of the mechanical properties of bamboo fiber-polypropylene composites (BaFPPC) by treatment of the fibers with CaCO 3 at various concentrations of the solution (0.05, 0.1, 0.2, and 0.3 mol l -1 ). CaCO 3 particles were successfully deposited in situ to bamboo fibers by means of ionic reaction of Na 2 CO 3 and CaCl 2 aqueous solution at various temperatures. Then BaFPPC were produced, and various tests on single fibers and the composites were performed. The compatibility between BaF and PP matrix was improved by the treatments. The crystallinity of inorganic materials was significantly affected by the reagent’s concentration. A 10.4% increase in tensile strength and a 16.7% increase in tensile modulus were observed after fiber treatment with CaCO 3 at a concentration of 0.2 mol l -1 .

The investigation of phase transition in powdered materials by dynamic mechanical analysis (DMA) is not straightforward because powders are difficult to prepare in a solid compact form without altering their structure and properties. In this study, a material pocket (MP) method has been applied to provide physical support to powdered samples for DMA testing (MP-DMA). Poplar wood strips and four types of wood particles [native wood flour (WF), α-cellulose (αC), holocellulose (HC), and particles without hemicelluloses (HR)] were treated with an ionic liquid (IL), 1-ethyl-3-methylimidazolium chloride ([Emim]Cl), to a weight percent gain (WPG) of 36%. Results show that all four [Emim]Cl-treated wood particles exhibited three apparent transition peaks over the measured temperature range. Paracrystalline cellulose, hemicelluloses, and lignin all exhibited a glass transition temperature ( T g ) at approximately 85°C due to the plasticizing effect of [Emim]Cl. The transition peak at a higher temperature may be due to the melting of crystalline cellulose in [Emim]Cl. MP-DMA is an effective tool for direct monitoring the phase transition of powdered lignocellulosics. This provides new insight into the interactions of ILs and cell wall polymers, and the method established can be easily extended to other systems based on powdered samples.

The response of dynamic and static modulus of elasticity (MOE dyn and MOE sta ) of red pine small clear wood (25.4×25.4×407 mm 3 ) within the temperature range -40 to 40°C has been investigated. The moisture content (MC) of the specimens ranged from 0 to 118%. The MOE dyn was calculated based on measured ultrasonic velocity ( V ) and wood density. The MOE sta was measured by static bending tests in a climate chamber between -40 and 40°C. The results indicate that both MOE dyn and MOE sta were affected by temperature and the MC. Above freezing point, MOE decreased linearly at a slow rate with increasing temperature. Below freezing point, MOE increased at a rapid rate with decreasing temperature. The MC-level had a significant effect on the MOE-temperature relationships. Temperature effect was much more significant in green wood than in dry wood. Analytical models were developed to predict the change of MOE dyn relative to that at 20°C in the case of acoustic measurements under different temperature conditions.

The proper parameters of sanding with abrasive sanding machine are significant to reduce energy consumption and to improve processing efficiency and quality. The parameters sanding speed, feed speed, and granularity have been investigated in terms of the sanding force (sF) and normal force (nF) for particle board (PB) and medium-density fiberboard (MDF). For PB, the sF and nF show decreasing trends of second power with increasing sanding speed and linear increase when feed speed increases. The sF and nF are almost constant when granularity increases from 40 to 80, but these forces show increasing trends of second power when granularity increases from 80 to 150. For MDF, the sF and nF change as trends of second power with increasing sanding speed and increase in trends of second power with increasing feed speed. The sF and nF force decrease when granularity increases from 40 to 80, but these forces present linear increasing trends when granularity increases from 80 to 150.

In this study, the extraction conditions of hemicelluloses from mixed hardwoods have been tested. In particular, 3% total titrated alkaline (TTA) green liquor (GL) was used to dissolve certain hemicelluloses and lignin in a manner similar to black liquor extraction, but the pH was maintained at near-neutral conditions, so that oligosaccharides were not completely degraded into isosaccharinic acids. The effects of temperature, time, and acid concentration on the fermentable sugar yields for the extract during secondary hydrolysis were investigated. Chips of mixed northern hardwoods were cooked in a rocking digester at 160°C for 110 min in the GL at a concentration of 3% Na 2 O-equivalent salts on dry wood. The mass of wood extracted into the GL extract was approximately 11.4% of the debarked wood mass, which resulted in a dilute solution of oligomeric hemicellulosic sugars. Dilute sulfuric acid hydrolysis was performed under the following conditions: 100°C–130°C, 2%–4% H 2 SO 4 , and 20–120 min residence time. The maximum fermentable sugar concentration of xylose, mannose, and galactose (XyMaGa) obtained from the hydrolyzed extract was 5.5 g l -1 , representing 91.7% of the maximum possible yield. A factorial design was used to study the effects of temperature and acid concentration on the maximum quantity of XyMaGa oligomers obtained in the extract during secondary hydrolysis. The maximum potential yield of XyMaGa reached 5.34 g l -1 at 130°C, 3.27% H 2 SO 4 , and 50.2 min residence time.