Formaldehyde emission from Particleboard and fiberboard

Formaldehyde emission from Particleboard and fiberboard

At present, the main adhesives used in the production of particleboard and MDF in China are urea-formaldehyde resin, whose products will continuously release free formaldehyde into the air. According to the information: as long as the air contains 0.1 mg/m3 of formaldehyde, it can smell its odor; when the concentration reaches 2.4-3.6 mg/m3, eyes, nose, pharynx and throat will be stimulated; long-term work and living in an environment with excessive formaldehyde gas content, according to the amount of formaldehyde absorbed by the human body, may lead to pharyngolaryngitis and conjunctivitis. Inflammation, dermatitis, eczema, gastritis, insomnia and visual impairment and other diseases, and even carcinogenic risk. In short, formaldehyde is harmful to human health. However, from the mechanism of formaldehyde release, it is impossible to completely eliminate formaldehyde release from Particleboard and fiberboard products when formaldehyde resin is used as adhesives. The key is to control its release. Therefore, formaldehyde emission is also one of the quality indicators of particleboard and fiberboard.

In China, perforation method is used to determine formaldehyde emission from Particleboard and MDF. The main instrument used is perforation extractor. The measuring principle of formaldehyde emission from Particleboard and MDF is exactly the same. This paper briefly describes the measuring principle.

The first step is to extract the free formaldehyde from the sample into water through perforation. The basic method is to add distilled water to the extraction tube and heat the sample and toluene in the flask, so that the free formaldehyde in the sample dissolves in toluene, which is a liquid-solid extraction process. The toluene vapor with formaldehyde passes through the bottom of the perforated plate of the extraction tube, and formaldehyde is transferred from toluene to water. This process is a liquid-liquid extraction process.

The second step is to quantify formaldehyde by iodometry. The basic method is: accurately absorb a certain amount of extract, titrate with a certain concentration of sodium thiosulfate, and record consumption. A blank test was conducted with distilled water of the same volume as the extract, and the amount of sodium thiosulfate solution used at this time was recorded.

Finally, the formaldehyde emission can be known by substituting the formula for calculation.

The quantitative determination of formaldehyde by iodometry is greatly influenced by the chemical composition of wood itself, especially medium density fiberboard. Therefore, acetylacetone colorimetry has been used abroad to quantify formaldehyde (such as European standards).

There are many factors affecting formaldehyde emission. The lower the molar ratio of formaldehyde to urea is, the lower the formaldehyde emission is. However, the decrease of molar ratio can easily change some properties of the glue and even affect the bonding strength. The formaldehyde emission of particleboard and fiberboard can be reduced by reducing the sizing amount and the moisture content of sizing material. In the process of hot pressing, increasing the hot pressing temperature and prolonging the hot pressing time will reduce the formaldehyde emission of the finished product. Reasonable use of curing agent and adding “aldehyde trapping agent” (such as urea, ammonia, etc.) can also reduce formaldehyde emission. In addition, the formaldehyde emission of spruce board is much lower than that of oak board. The formaldehyde emission of sawdust board is about 10 times higher than that of particleboard.

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