Volume 71, Issue 11

A partial cationization of cellulosic pulps has been suggested to enhance the retention of fillers and fines in the paper and board manufacturing industry. The challenge is the highly crystalline structure of cellulose and the mass transfer limitations of softwood fibers, which are long and resistant to and hinder the chemical reactions. In the present paper, it was demonstrated that refining (leading to decrystallization) and alkaline treatments facilitate the subsequent cationization process with quaternary ammonium groups. Cationization was performed with 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) at 120°C for 2 h, and degrees of substitution above 0.3 were achieved. Beating to 4000 or 4500 PFI revolutions was found to be an optimum to achieve these high degrees of substitution. Mixing a small percentage (4%) of cationized pulp (with a charge density of approximately 0.8 meq g −1 ) with the untreated pulp could compensate for the negative surface charge of the original fibers. In this way, the highest charge density and opacity of the paper and the best retention of fines were achieved. If cationization was implemented in a paper mill, it should follow, not precede, the refining stage.

Cinnamomum kanehirae Hay. is endemic in Taiwan and is severely threatened due to intensive utilization and illegal logging. To combat illegal logging, suitable identification markers are needed, which are usable in a court of law, such as microsatellite marker for genotyping. In the present paper, a genetic fingerprinting database was generated based on 15 microsatellites, which are suitable to assess the timber’s origin and its population genetic structure. The quality of DNA extractions from C. kanehirae timbers was assessed by comparing cpDNA trn L– trn F sequence lengths. The cumulative probability of identifying unrelated individuals in these microsatellites was 5.151×10 −17 . The results indicate that the low genetic diversity is a consequence of illegal logging and that there is a significant genetic differentiation among C. kanehirae populations. It was possible to trace back the geographical origin of unknown C. kanehirae timbers based on a genetic reference database, i.e. all blind wood samples were assigned to their true geographical origins. Accordingly, microsatellites are a useful tool to identify the population origins of timbers and can be considered as a tool for combating illegal logging of C. kanehirae .

The present work focusses on the loss of resilience of torrefied wood as an indicator of its grindability. An impact device was developed to evaluate the mechanical behaviour of wood at high compression rates with a particular emphasis on the surface area of the particles produced. It allows the energy determination needed to produce particles without a traditional grinding test. Pine ( Pinus pinaster ) and oak ( Quercus robur ) were tested in radial (R) and tangential (T) directions and for various torrefaction intensities. With increasing heat intensity, the material becomes more fragile and finally loses its fibrous character, which increases the number of peak events on the stress/strain curve and significantly reduces the deformation energy. Two indices were derived from the experimental results: the apparent stiffness during failure (ASF) and the specific failure energy (SFE). These criteria allow the quantification of the loss of mechanical strength due to torrefaction, as well as the surface area increment of particles for a given grinding energy.

Cross-laminated timber (CLT) panels – consisting of several cross-wise stacked layers of glued boards – have a high dimensional stability. However, the outer surfaces of CTL are exposed to environmental humidity changes and thus to swelling and shrinking. To improve CLT’s dimensional stability further, the layers of kiln dried (KD) CLT were substituted partly (on the surfaces) and entirely with superheated steam treated (SHST) wood. The effects of SHST wood and the performance of the one-component polyurethane resin (PUR) were tested by block shear and delamination tests after water soaking. Under various conditions, the shear strength ranged from 1.3 MPa to 4.7 MPa and the wood failure percentage (WFP) from 76% to 92%. The optimal parameter were ascertained as pressing time (30–45 min), pressure (0.98 MPa) and adhesive amount (175–200 g m −2 ). The water soaked delamination of CLT manufactured with SHST wood was approximately 50% lower than that of CLT made of KD wood.

The migration of bound water and free water has been investigated during microwave drying of wood by the time domain nuclear magnetic resonance (TD-NMR) technique. Both the heartwood (hW) and sapwood (sW) of Beijing poplar ( Populus beijingensis W. Y. Hsu) and Qingpi poplar ( Populus platyphylla T. Y. Sun) were studied. The microwave drying is characterized by a fast drying rate, and there is a linear relation between moisture content (MC) and microwave drying time ( t ). The drying rate of free water is about 2.7 times more rapid than that of bound water. The spin-spin relaxation time (T2) revealed that most of the water was free water situated in smaller pores. The irregular T2 signal amplitudes of free water in hWs indicated that fractional water in smaller pores was transferred into bigger pores during drying.

To know the minimum moisture threshold (MMThr) in wood allowing for the initiation of the fungal decay by basidiomycetes is relevant both from a theoretical and a practical point of view. The present work summarizes the knowledge about MMThr and presents experimental data obtained by improved laboratory decay tests on Picea abies (Norway spruce) and Fagus sylvatica (European beech) with the fungi Coniophora puteana and Trametes versicolor under different exposure scenarios well suited for simulation in real applications. The three experimental set-ups, in which the pile tests play a pivotal role, differed in terms of external moisture supply and the inoculation strategies. It was confirmed that wood-destroying basidiomycetes are able to degrade wood at high relative humidity without any external source of available liquid water. The method of moistening the wood samples has an effect on the MMThr before initiation of the fungal decay, but different basidiomycetes were able to cause significant decay at moisture contents considerably below the fiber saturation point.

Pine and spruce heartwood and sapwood were milled to wood particles and the volatile organic compounds (VOCs) of the wood particles were tested against four bacterial strains. To study the influence of relative humidity on the antibacterial effect, both dry and wet wood particles were tested. Twenty microliters of the bacterial dilution with a concentration of 1.5×10 7 CFU ml −1 was cultured on glass surfaces in the presence of VOCs and the amount of viable bacteria was studied after 2, 4, and 24 h. The volatile emissions were evaluated by GC/MS and the results were compared with the results from the bacterial trial. VOCs had an antibacterial effect on Escherichia coli, Streptococcus pneumoniae and slightly on Salmonella enterica serovar Typhimurium. But the effect on Staphylococcus aureus was minute even after 3 days’ incubation. The dry wood particles generally had a stronger antibacterial effect, though the amount of VOCs from the wet wood was higher. Pine heartwood had the strongest antibacterial effect and also the highest emissions of VOCs. However, the interaction between different bacterial strains and wood species shows some variations.

Ozonized Japanese cedar wood meal was evaluated as a feedstock for compost. The composting experiment performed in a 1.8 m 3 tank during a 4-week period showed that the decomposition of organics was accelerated by the ozonation of wood meal during thermophilic phase. The same is true for decay test of white-rot (WR) fungus. The tested brown-rot (BR) fungus did not show any effect. Accordingly, the lignin degradation by ozone is advantageous for composting. In addition, liberation of ammonia, one source of odor development, was suppressed during the thermophilic phase of composting of ozonized wood meal.

Four-point key-hole side-edge-notched bending (4KHSENB) tests of medium-density fibreboard (MDF), a quasi-isotropic material, were conducted. The experimental results were analysed via data reduction methods, including the elementary beam theory (EBT), the point stress criterion (PSC), the average stress criterion (ASC) and linear elastic fracture mechanics (LEFM), which are applicable to MDF specimens. The PSC and ASC approaches accurately predicted the relationship between the nominal critical stress at the onset of nonlinearity and the notch length. The same is true for predicting the relationship between the nominal bending strength and the notch length.