X-ray photoelectron spectroscopy determination of urea formaldehyde resin coverage on MDF fibre

Quantification of fibre resin coverage is essential for the understanding of panel integrity in medium density fibreboard (MDF) and similar panel products. X-ray photo-electron spectroscopy (XPS) was used to determine the proportion of fibre surface covered by nitrogen containing UF resin in blowline resinated and dry-blended MDF. Coverage values were dependent on processing variables such as resin content, wax content, resin spray droplet size and for blowline resination, the position of the resin injection nozzle along the blowline. Comparison of XPS coverage values with those obtained using confocal laser scanning microscopy (CLSM) revealed substantially differing absolute resin coverage of fibre between the two techniques. For dry-blended panels there was a correlation between the two techniques. However, grouping resin coverage values having more than one processing variation did not establish any relationship between XPS and CLSM coverage values, whether for dry-blended or blowline resinated MDF. Wax movement as well as deposition of other materials on the fibre surface during hot pressing were observed to contribute to lower surface %N content, which may limit the usefulness of the XPS technique.