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Engineering plastics from lignin. I. Synthesis of hydroxypropyl lignin
Author(s) -
Wu Leo C.F.,
Glasser Wolfgang G.
Publication year - 1984
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1984.070290408
Subject(s) - lignin , chemistry , carboxylation , kraft paper , propylene oxide , organic chemistry , kinetics , alkoxide , depolymerization , reaction mechanism , polymer chemistry , chemical engineering , ethylene oxide , catalysis , polymer , copolymer , physics , quantum mechanics , engineering
Abstract Hydroxypropylation of lignin in a batch reactor under alkaline conditions at 180°C was studied using propylene oxide (PO) by itself, and PO in combination with several ligninlike model compounds and with kraft lignin. While the PO homopolymerization rate increased rapidly at temperatures above 85°C, and was too fast to be determined accurately at 180°C, the addition of model compounds and lignin was found to delay homopolymerization in relation to the presence of ionizable functional groups. The observations are consistent with a reaction mechanism involving first order kinetics with regard to each alkoxide and PO concentrations. Where the reaction rates toward PO increase with increasing pK a values, the reaction sequence proceeds in the order of declining basicity. Thus lignins with high acidity were found to be subject to greater degrees of modification than those with more neutral character. This explains the earlier observed beneficial effect of lignin carboxylation on the properties of lignin–PO reaction mixtures.