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Gewählte Doctoral Thesis:

Elfriede Maria Hogger (2020): ENGINEERING OF RESIN PROPERTIES IN PLYWOOD PRODUCTION Focusing on cold tack analysis and resin modification by additives.
Doctoral Thesis - Institut für Holztechnologie und Nachwachsende Rohstoffe, BOKU-Universität für Bodenkultur, pp 124. UB BOKU obvsg

Data Source: ZID Abstracts
Abstract:
The plywood process involves many steps important for the quality of the results. The selection of adhesives and usage or manipulation of properties are amongst them. There is often a lack of scientifically sound information on the optimal use of these, and much is based on operational experience. Two areas of plywood production process were addressed and systematically and scientifically investigated, to create a database for research, plywood and resin producers to base decisions on. Cold tack development was investigated on urea formaldehyde (UF) resin. Cold tack is used during prepressing of veneer stacks to ensure the they stick together until transported to a hot press. The influence of lay-up time, resin amount and age, veneer moisture content (MC) and temperature, and pre-press time on cold tack and later on cured bond line were investigated. The highest effect was found for MC and temperature, but no significant effect on the cured bond line was seen. The optimization of resin systems used in plywood production (urea and phenol formaldehyde) by adding additives was also investigated. It has been common practice for decades, but the addition is usually based on operational experience. There are various additives, with cereal flours, being the most commonly used, but basic scientific knowledge is hardly available for adhesive applications. Focus was the systematic scientific study of the effect of wheat flour and its main components as extenders for existing adhesive systems. Physico-chemical properties of resins were tested, as well as the development of bonding strength, performance of produced panels in wet conditions and formaldehyde emissions. Protein showed the strongest influence on viscosity, while the curing behavior of the resins was not affected. It was possible to replace half of the UF resin with wheat flour and add up to 30% of protein to PF resin-based boards to achieve sufficient shear strengths. Formaldehyde emissions were not affected.

Betreuer: Konnerth Johannes
1. Berater: Van Herwijnen Hendrikus
2. Berater: Gindl-Altmutter Wolfgang

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