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Gewählte Doctoral Thesis:

Masoumeh Ghorbani (2017): Lignin-based Phenolic Adhesives for Wood-based Materials.
Doctoral Thesis - Institut für Holztechnologie und Nachwachsende Rohstoffe, BOKU-Universität für Bodenkultur, pp 108. UB BOKU obvsg

Data Source: ZID Abstracts
Substituting bio-resources for phenol in phenol-formaldehyde (PF) resins is still highly demanded by wood adhesive industries to be commercialized. To bring the bio-based PF resins significantly into the market, a wide range of lignin types was studied in terms of its reactivity towards formaldehyde and different modifications were applied to boost the reactivity. At first, different types of lignin from different species and pulping processes were screened for utilization in PF resin preparation. These eight different lignin types were sarkanda grass soda lignin, wheat straw soda lignin, pine kraft lignin, beech organosolv lignin and ammonium, calcium, magnesium and sodium lignosulfonates. As general findings all types of lignin accelerated viscosity development of lignin-phenol-formaldehyde resin during synthesis, depending on the level of phenol replacement. The maximum substitution level used here was 40% wt. Among the lignin sources used, pine kraft lignin and sodium lignosulfonate were the best performing types. In the second step, different modifications i. e. phenolation, methylolation and ammoxidation were performed. Although phenolation and methylolation were already reported as effective methods in previous studies, ammoxidation was used for first time in phenolic adhesive synthesis. Each individual method increased the reactivity-related parameters of the lignin used, however, no improvement in the resin properties was observed. As a novel modification approach, a combination of Fenton-type oxidation and ammoxidation was applied to pine kraft lignin. The two-stage modification significantly accelerated resoles synthesis and curing for 40 wt% phenol replacements, whereas bond formation speed could again not be improved. Nanoindentation assessing the mechanical properties of the polymer matrix present in the bonds showed that replacement of phenol by non-modified or modified kraft lignin had no negative impact on the mechanical properties of the cured resins. Eventually the end product performance of the LPF resins was evaluated via manufacturing solid wood joints, plywood and paper-based high pressure laminates. For all these products produced with pine kraft lignin based resins the standard requirement for out-door usage could be fulfilled.

Betreuer: Konnerth Johannes
1. Berater: Liebner Falk

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