Kohta Miyamoto

Effect of particle shape on linear expansion of particleboard

Hinoki (Japanese cypress) strand with 0.6mm thickness was hammer-milled to prepare three types of particles that had the same thickness but different lengths and widths. Screen analysis and image analysis were conducted to evaluate the shape and distribution of the particle dimensions. Laboratory-scale particleboards were fabricated at three density levels using these particles. To determine the true effect of particle shape on the linear expansion (LE) of the board, these boards exhibited almost the same temperature behavior during pressing, the same density profile, and the same bending properties at each board density level. LE at 40°C and 90% relative humidity of the board was found to be affected by the particle shape. The board composed of small particles showed a larger LE at the same density level. It was considered that the out-of-plane orientation angle of the particles affected the LE of the boards. Thickness swelling and internal bond strength were also affected by the particle shape.

Effect of manufacturing parameters on the linear expansion and density profile of particleboard

Particleboards were fabricated in the laboratory with different board densities and resin contents to evaluate linear expansion when exposed to both vapor and liquid water. Density profiles were measured to determine the relation to the elastic constants and to the dimensional properties of the boards. It was found that density profiles were affected by the board density and resin content applied. The high-density layer formed in the thickness direction affected the elastic constant measurements. A model introduced to predict the linear expansion closely matched the data during exposure to water. Under conditions of 40°C and 90% humidity, linear expansion increased with increasing board density. An increase in resin content from 6% to 12% slightly increased the linear expansion and decreased the thickness swelling. A linear relation was found between board density and linear expansion per unit of moisture content change.

Acetaldehyde emission from glued-laminated timber using phenol-resorcinol-formaldehyde resin adhesives with addition of ethanol

Volatile organic compounds (VOCs) from wood-based materials have been a topic of great concern as one of the causes of sick building syndromes for decades. According to an investigation of indoor air quality of new residences by the Japanese Ministry of Land, Infrastructure and Transport, about 9% of all residences exceeded the guideline value of 48mg/m (0.03ppm) of acetaldehyde concentration. Other studies have also shown excessive acetaldehyde concentration in indoor air in wooden houses. Most natural wood has a certain level of acetaldehyde emission (5–130mg/mh after 1 day) measured by small chamber methods. The amount of acetaldehyde emission is considered to depend on the wood species, although the mechanism of acetaldehyde emission has been unclear. Recently there have been multiple reports in which extraordinary acetaldehyde emissions (600–1500mg/mh) from glued– laminated timbers and laminated veneer lumbers bonded with phenol–resorcinol–formaldehyde (PRF) resin adhesives have been measured using small chamber methods. These values are much higher than the natural acetaldehyde emission from wood. However, as yet, we have not found any feasible answer regarding the origin of the acetaldehyde. It is necessary to elucidate the source of the extraordinary acetaldehyde emission as soon as possible. In general, two types of commercial PRF resins containing methanol and/or ethanol have been used. In addition, radio frequency or cold press techniques are commonly used in the laminating process in the industry. In this study, therefore, the effect of PRF type, press condition, and wood species on acetaldehyde emission from glued– laminated timber was investigated using the small chamber method.

Effects of press closing time on mat consolidation behavior during hot pressing and on linear expansion of particleboard

Mat consolidation behavior was investigated at various press closing times (PCTs) using hinoki (Japanese cypress) particle mats. The temperature in the core layer of the mat, press pressure, and platen distance were measured. At the plateau stage during hot pressing, the core temperature decreased with increasing PCT. The core temperature did not increase before the platen distance equaled the target board thickness in the PCT range of 4–50 s and rose slightly when the PCT exceeded 100s. There was a linear relation between the logarithm of PCT and the maximum press pressure. The density profile across board thickness was strongly affected by the PCT. As the PCT increased, the position of the peak density (PD) moved toward the core layer as the PD itself decreased. The effect of PCT on the linear expansion (LE) of the board is discussed in relation to the density profile. There was no difference in LE after high relative humidity treatment in the PCT range 4–50s. LE appeared to be related to the low density and the precured region of the board surface. The LE after drying treatment was around −0.1%, and the thickness swelling after high relative humidity and drying treatments increased with increasing PCT.

Evaluation of equivalence of desiccator methods in the ISO and JIS standards

In ISO/TC89, the measuring method of formaldehyde emitted from wood-based materials was discussed, and the ISO standard of the desiccator method was enacted in 2008. There are some differences between the desiccator methods according to JIS and ISO standard and therefore, the experimental equivalence is not evident. In this study, equivalence of the cooling processes of the test solution was evaluated because the operational procedures in the JIS and ISO standards are different.

Volatile organic compounds (VOCs) from lauan (Shorea ssp.) plyboard prepared with kraft lignin, soy flour, gluten meal and tannin: emissions during hot pressing and from panels as a function of time

Abstract Soy and corn gluten proteins are common ingredients in adhesives and resins together with kraft lignin and condensed tannin. The relative contribution of these additives to volatile organic compound (VOC) emissions in the course of processing hardwood veneer products was evaluated. Press emissions were captured and separated into condensate and gaseous fractions. High-performance liquid chromatography (HPLC) was employed to characterize aldehydes in condensate and gaseous fractions, while GCMS served for identification and quantitative determination of the compounds in the gas phase. Aldehydes dominate the press emissions with both proteinaceous binders producing significantly higher formaldehyde (FA), acetaldehyde (AcA) and hexaldehyde (hexA) emissions compared to pressed veneer without additives. Other aldehydes, including valeraldehyde and propionaldehyde were also captured, but in relatively lower amounts. In contrast, lignin as a binder led to lower FA content in press emissions, whereas tannin significantly reduced contributions of FA, AcA and other aldehydes. VOC emissions from plywood panels during chamber testing were similar to compounds evolved on hot-pressing.

Correction to: Acetaldehyde emission from wood induced by the addition of ethanol

The article Acetaldehyde emission from wood induced by the addition of ethanol, written by Shin-ichiro Tohmura, Atsuko Ishikawa, Kohta Miyamoto and Akio Inoue, was originally published Online First without open access.