Technology for Wood and Natural Fiber-Based Materials

Research Project

Reclassification of formaldehyde – Alternative formaldehyde-free urea resins for wood-based materials and decorative paper coatings

This project is a continuation of the project “Formaldehyde-free melamine resins as a binding agent for low-emission wood-based materials and impregnation resins for decorative coatings”. Building upon the knowledge gained from the prior project, the development of formaldehyde-free, low-cost (compared to melamine resins) urea resins for use as adhesives in wood-based materials and as impregnation resins for decorative paper coatings now seems promising.

© Fraunhofer WKI | Manuela Lingnau
Wood-based boards and decorative coating

As alternatives to formaldehyde, further aldehydes are now available in principle for manufacturing formaldehyde-free amino polymer resins. Some alternative aldehydes have the disadvantage that they can cause discoloration, are to a certain extent toxic, volatile or not reactive enough, or that their solubility causes problems.

The results of the investigations so far show that there may be solutions to allow formaldehyde-free melamine glyoxylic acid / glyoxal resins to be used as adhesive for particle board, medium-density fiberboard (MDF) and plywood with very low formaldehyde emissions (caused by the wood particles). Melamine glyoxylic acid / glyoxal resin can also be used in cement-bound particle board to improve the workability of the cement bonding and the board’s mechanical properties. Further research is necessary to assess the potential and cost-effectiveness of formaldehyde-free melamine resins in industrial applications.

For reasons of cost, melamine and melamine resins are currently used only to a limited extent as reinforcing components in urea formaldehyde resins (UF resins) in industrial wood-based materials. The adhesive manufacturers therefore have to develop new, low-cost adhesives (particularly due to the current moves to reclassify formaldehyde as Class 1B) and the wood-based material manufacturers have to adapt their press conditions to these new adhesives. A cost-effective and technically acceptable formaldehyde-free adhesive alternative to UF resin is currently not available.

Initial tests on high-density fiberboard (HDF) show that melamine urea glyoxal resin can, in principle, achieve the properties of an HDF board made with UF resin.

 

Table 1: Mechanical and hygric properties of 8mm-thick HDF boards with melamine urea glyoxal resin (MHG) and UF resin as a reference

Resin

Press duration

Board characteristic

Density

Bending strength

Bending modulus of elasticity

Transverse tensile strength

Thickness swelling 24h

 

s/mm

kg/m³

N/mm²

N/mm²

N/mm²

%

MHG-Harz

22

722

16,3

1902

0,31

27,1

UF-Harz

22

717

25,5

2472

0,5

16,5

DIN EN 622-2:2004 an Typ HB

≥ 25

k.A.

≥ 0,5

≥ 25

 

Project Partner

Fraunhofer-Institut für Angewandte Polymerforschung (IAP)

Funding

Federal Ministry for Economic Affairs and Energy (BMWi) trough Arbeitsgemeinschaft industrieller Forschungsvereinigungen »Otto von Guericke« e.V.

Internationaler Verein für Technische Holzfragen (iVTH) e.V.

IGF project reference:    18558 BG

Project duration:       01.01.2015 – 30.06.2017