Biopolyols obtained via microwave-assisted liquefaction of lignin: structure, rheological, physical and thermal properties
The present study examined the application of polyols obtained via microwave-assisted liquefaction of lignin in the production of rigid polyurethane foam. Lignin was liquefed in crude glycerol and 1,4-butanediol at diferent temperatures (130–170 °C), without a catalyst and using various biomass concentrations (15 and 30 wt%). The physicochemical properties, process yield, and FTIR-based identifcation of the obtained polyols were investigated. Under optimal conditions, i.e., a 5-min microwave heating time and a reaction temperature of 150 °C, a polyol characterized by a suitable hydroxyl number of 670 mg KOH/g was obtained with a 93% process yield. Liquefed biopolyol was directly used for the production of rigid polyurethane foams with the addition of polymeric diphenylmethane diisocyanate at the [NCO/OH] ratio of 2:1. Mechanical properties of the obtained foams gradually improved with increasing content of biopolyol. The 5% weight loss temperature (T5) for bio-based foams was higher, respectively 6 and 13 °C compared to the petrochemical foam. Replacement of petrochemical polyether with biopolyols showed the ability to obtain rigid polyurethane foams from lignin and crude glycerol.
Kamila Gosz, Paulina Kosmela, Aleksander Hejna, Grzegorz Gajowiec, Łukasz Piszczyk. (2018). Biopolyols obtained via microwave-assisted liquefaction of lignin: structure, rheological, physical and thermal properties, 52(3), 599-617. https://doi.org/10.1007/s00226-018-0991-4
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