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Combination of different analytical methods for the investigation of UF- and MUF-adhesives

: Grunwald, D.

WOOD K PLUS, Kompetenzzentrum für Holzverbundwerkstoffe und Holzchemie, Wien:
Wood based materials. Wood composites and chemistry : International symposium, September 19-20, 2002, Vienna, Austria
Wien, 2002
International Symposium "Wood Based Materials" <2002, Wien>
Fraunhofer WKI ()
UF-adhesive; MUF-adhesive; analysis; wood-based panel; UF-Klebstoff; MUF-Klebstoff; Analyse; Holzwerkstoff

More than 80 different industrially produced UF- and MUF-adhesives were analysed by several techniques (GPC, NMR, chemical analysis). All results were evaluated by two different statistic methods (principal components analysis and cluster analysis). The results show correlations only within one analytical technique. It has to be accepted that results determined by different analytical techniques are difficult to compare. To characterise an adhesive it is necessary to use the analytical methods carefully. Nevertheless one new relation was discovered between the number-average of molecular weight (Mn) and the ratio of formaldehyde to amino groups (F/NH2), which is equal to the molar ratio (U:F or M:U:F). In the adhesives formaldehyde does not react as a crosslinking but only as an elongation agent. An uncured adhesive is composed of mostly linear molecules with some potential crosslinking centres.