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Polymers 2017, 9(2), 43; doi:10.3390/polym9020043

Ammoxidized Fenton-Activated Pine Kraft Lignin Accelerates Synthesis and Curing of Resole Resins

1
Department of Material Sciences and Process Engineering, Institute of Wood Technology and Renewable Materials; University of Natural Resources and Life Sciences Vienna, University and Research Center Tulln, Konrad-Lorenz-Strasse 24, 3430 Tulln an der Donau, Austria
2
Department of Chemistry, Division of Chemistry of Renewable Resources, University of Natural Resources and Life Sciences Vienna, University and Research Center Tulln, Konrad-Lorenz-Strasse 24, 3430 Tulln an der Donau, Austria
3
Kompetenzzentrum Holz GmbH, Altenberger Strasse 69, 4040 Linz, Austria
4
Chair of Chemistry of Polymeric Materials & Christian Doppler Laboratory for Functional and Polymer Based Ink-Jet Inks, University of Leoben, Otto-Glöckel-Strasse 2, A-8700 Leoben, Austria
*
Author to whom correspondence should be addressed.
Received: 30 December 2016 / Revised: 19 January 2017 / Accepted: 22 January 2017 / Published: 28 January 2017
(This article belongs to the Special Issue Renewable Polymeric Adhesives)
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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. View Full-Text
Keywords: lignin; phenol formaldehyde resin; lignin ammoxidation; Fenton-type oxidation; ligneous adhesive; automated bonding evaluation system (ABES) lignin; phenol formaldehyde resin; lignin ammoxidation; Fenton-type oxidation; ligneous adhesive; automated bonding evaluation system (ABES)
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MDPI and ACS Style

Ghorbani, M.; Konnerth, J.; Budjav, E.; Silva, A.R.; Zinovyev, G.; van Herwijnen, H.W.G.; Edler, M.; Griesser, T.; Liebner, F. Ammoxidized Fenton-Activated Pine Kraft Lignin Accelerates Synthesis and Curing of Resole Resins. Polymers 2017, 9, 43.

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