Ammoxidized Fenton-Activated Pine Kraft Lignin Accelerates Synthesis and Curing of Resole Resins
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Authors
Organisational units
External Organisational units
- BOKU
- Wood K Plus Kompetenzzentrum Holz GmbH
- Chrstn. Doppler Lab. for Functional and Polymer Based Ink-Jet Inks -Astr Otto Glockel-Strasse 2
Abstract
Ammoxidation of pine kraft lignin in aqueous 5 wt % ammonia affords a novel type of phenol substitute that significantly accelerates resole synthesis and curing as demonstrated for 40 wt % phenol replacement. Compared to non-ammoxidized lignin, which already shortens significantly the cooking time required to reach a resole viscosity of 1000 Pa·s (250 vs. 150 s) and reduces the typical curing B-time by about 25% at 100 °C, the use of ammoxidized lignin has an even more pronounced impact in this respect. Activation of lignin by Fenton-type oxidation prior to ammoxidation further boosts both synthesis and curing of the resole. This is presumably due to the intermediary formation of polyvalent cross-linkers like N,N,N-tris (methylol) trimethylene triamine triggered by saponification of a larger fraction of nitrogenous moieties present in such a treated lignin (ammonium salts, amide-type nitrogen, urea) and reaction of the released ammonia with formaldehyde. Except for the fact that phenol replacement by ammoxidized lignin results in a somewhat less brittle cured adhesive polymer and higher elastic modulus, the aforementioned acceleration in curing could no longer be observed in the presence of wood, where a significantly delayed wood-adhesive bond formation was observed for the lignin-containing adhesives as evident from the automated bonding evaluation system.
Details
Original language | English |
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Article number | 43 |
Number of pages | 17 |
Journal | Polymers |
Volume | 9.2017 |
Issue number | 2 |
DOIs | |
Publication status | Published - 28 Jan 2017 |