Novel wood adhesives from bio-based materials and polyketones

PhD ceremony: Ms. A.I.M. Hamarneh, 13.15 uur, Academiegebouw, Broerstraat 5, Groningen

Thesis: Novel wood adhesives from bio-based materials and polyketones

Promotor(s): prof.dr. F. Pichioni, prof.dr.ir. H.J. Heeres

Faculty: Mathematics and Natural Sciences

The current market for wood adhesives is predominantly based on fossil derived formaldehyde-containing resins. The emissions of formaldehyde from such adhesives is known to be harmful to the environment and suspected to be carcinogenic. Besides, the current high and very instable oil prices and the trend towards the use of greener bio-based chemicals have stimulated the search for environmentally friendly wood adhesives.

Biomass and other natural resources are abundantly available and may serve as interesting starting material for the preparation of inexpensive, biodegradable, and renewable (components in) wood adhesive formulations. Well known examples are the use of proteins, casein, and carbohydrates etc.. Unfortunately, natural resource based or derived wood adhesives have some major drawbacks compared to conventional ones such as a relatively low strength, low water resistance, and sensitivity to biological attack.

Recently, wood adhesives based on formaldehyde-free polyketones have been developed and shown to have outstanding performance. These novel adhesives are used as water emulsions and prepared according to a two step procedure. In the first step, a polymeric amine is prepared by reacting the virgin polyketone with a di-amine using the Paal-Knorr approach. Subsequently, an additional amount of virgin polyketone in water is added. The polymeric amine acts as a surfactant in the emulsions. However, there are some drawbacks related to the use of these polyketone/amine based wood adhesive formulations such as their limited flexibility in terms of the final formulation (a narrow range of available total solid contents to give stable dispersions) and the currently limited availability of polyketones in larger quantities.

In this work, renewable soy and Jatropha curcas L. proteins were co-formulated into the basic recipe of the polyketone/diamine adhesives. All protein-containing emulsions passed the European standard (EN-314) wood test with higher shear strength than required. The main advantages of the polyketone/amine/protein based formulations are a reduced cost of the overall formulations compared to polyketone/amine formulations alone and improved emulsion stability.