Gas Analysis Method for Wood-Based Panels
Impact of wood-based panel moisture content on the gas analysis value
Formaldehyde is a component in many adhesives of wood-based products, but natural wood also emits formaldehyde in small amounts - as do almost all organic materials. Formaldehyde is considered a carcinogenic substance.
Background and Objective
Formaldehyde was classified in 2004 by the International Agency for Research on Cancer (IARC) of the World Health Organization as "carcinogenic to humans". Since then, this substance has been the subject of intense debate. In wood products it can be found in the adhesives, but they have to comply with a limit of 0.1 ppm (according to GefStoffV). The limit is determined based on the so-called chamber method (EN 717 Part 1, reference method); this method is very sensitive and can determine even low formaldehyde emissions from materials. However, in this case a minimum of 10 days must be estimated for each measurement; so this method is not suitable for the quality control of glued wood products. Therefore, there are a number of standardized and established test methods that provide results within a short period of time (few hours). They correlate well with the reference method. During the production control of wood-based materials with particularly low formaldehyde emissions, it was found that the previous standard method (DIN EN 120, perforator) is not sufficiently accurate and exact in the variability of the products. Another method (DIN EN 717-2, gas analysis) performs very well, but it lacks sufficient testing, especially for uncoated chipboard and fibreboard, because this method has been used so far only for plywood and coated board materials.
In our project we want to investigate and optimize the parameters of the gas analysis method in order to determine the release of formaldehyde effectively, more quickly, and more stable in the same time. The aim is to shorten the test time as well as to identify other relevant parameters for the measurement procedure. As a first step the influence of the material moisture is being correlated with the result of gas analysis.
So far, very good correlations between the material moisture and gas analysis for each individual panel type (e.g., E1-grade particleboard) were determined. However, we doubt at this stage that a general relationship can be determined because the relationship of moisture and gas analysis for different panel types differed. This requires further analysis. In addition, we have discovered an interesting side aspect: For a particular panel type a substantial and lasting reduction of formaldehyde emissions was observed under defined conditions. This effect could be repeated several times. Further investigations have to show what caused this significant reduction of formaldehyde, and whether potential exists for a practical application.