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Ammoxidized Fenton-Activated Pine Kraft Lignin Accelerates Synthesis and Curing of Resole Resins.
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- المؤلفون: Ghorbani, Masoumeh1 ; Konnerth, Johannes1 ; Budjav, Enkhjargal2 ; Silva, Ana Requejo2 ; Zinovyev, Grigory2 ; van Herwijnen, Hendrikus W. G.3 ; Edler, Matthias4 ; Griesser, Thomas2
- المصدر:
Polymers (20734360). Feb2017, Vol. 9 Issue 2, p43. 17p. 1 Diagram, 7 Charts, 7 Graphs.
- الموضوع:
- معلومة اضافية
- نبذة مختصرة :
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. [ABSTRACT FROM AUTHOR]
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