Shin-ichiro Tohmura

Influence of the melamine content in melamine-urea-formaldehyde resins on formaldehyde emission and cured resin structure

The effect of melamine content in melamine-urea-formaldehyde (MUF) resins on the formaldehyde emission and resin structure was investigated using six MUF resins synthesized with different F/(M + U) and M/U molar ratios. The formaldehyde emission from the plywood decreased as the F/(M + U) molar ratio decreased and the M/ U molar ratio increased. In addition, the bond performance was enhanced as the M/U molar ratio increased in the MUF resins with a fixed F/(M + U) molar ratio. Quantitative solution13C-NMR spectra of MUF resins revealed that the MUF resins with a high melamine content consisted of more highly branched crosslinkage structure and free melamine compared to the resins with low melamine contents. Furthermore, solid-state13C CP-MAS NMR spectra of cured MUF resins proved that more methylol groups, dimethylene ether, and branched methylene structures were present in the MUF resins with a higher F/(M + U) molar ratio, leading to increased bond strength and formaldehyde emission. There is no significant difference in the linkage structure of the cured resins with the same F/(M + U) and different M/U molar ratios except the ratios of carbonyl carbon of urea and triazine carbon of melamine. Therefore, the lower formaldehyde emission from cured MUF resins with a higher M/U molar ratio might be ascribed to the stronger linkages between triazine carbons of melamine than those of urea carbons. Consequently, the melamine contributed to strong crosslinking linkages in the cured resin structures, leading to lower formaldehyde emission and better bond performance.

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 Ethanol-Supplemented Phenol-Resorcinol-Formaldehyde Resin on Formaldehyde and Acetaldehyde Emissions from Glued-Laminated Timbers*

Abstract Aldehyde emissions from glued-laminated timbers bonded with phenol-resorcinol-formaldehyde (PRF) resin adhesives, some of which included ethanol as a solvent, were investigated. Four comme...

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.