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

Research output: Contribution to journalArticleResearchpeer-review

Authors

  • Masoumeh Ghorbani
  • Johannes Konnerth
  • Enkhjargal Budjav
  • Ana Requejo Silva
  • Grigory Zinovyev
  • Hendrikus W. G. van Herwijnen
  • Falk Liebner

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 languageEnglish
Article number43
Number of pages17
JournalPolymers
Volume9.2017
Issue number2
DOIs
Publication statusPublished - 28 Jan 2017