Durable Biopolymer Films From Lignin-Carbohydrate Complex Derived From a Pulp Mill Side Stream

Publisher Copyright: Copyright © 2021 Asikanius, Jääskeläinen, Koivula, Oinonen and Österberg.Valorization of side streams offers novel types of raw materials to complement or replace synthetic and food-based alternatives in materials science, increasing profitability and decreasing the environmental impacts of biorefineries. Lignocellulose biomass contains lignin and carbohydrates that are covalently linked into lignin-carbohydrate complexes (LCCs). In biomass fractionation processes, these complexes are conventionally considered as waste, which hinders the biomass fractionation process, and they may solubilize into aqueous effluents. This study presents how LCCs, derived from pulp mill effluent, can be turned into valuable biopolymers for industrial polymer film applications. Free-standing composite films containing hydroxyethyl cellulose (HEC) and LCCs with varying molar mass, charge density and lignin/hemicellulose ratio were prepared to study the effect of LCC amount on mechanical properties and oxygen permeability. Increasing the LCC content increased the yield point and Young’s modulus of the films. Breaking strain measurements revealed a non-linear correlation with the LCC concentration for the samples with higher lignin than hemicellulose content. The addition of LCC enhanced oxygen barrier properties of HEC films significantly even at high relative humidity. The present research demonstrates how a currently underutilized fraction of the biorefinery side stream has the potential to be valorized as a biopolymer in industrial applications, for example as a barrier film for paper and board packaging.Peer reviewe

Natural and artificial ageing of spruce wood as observed by FTIR-ATR and UVRR spectroscopy

Spruce samples, naturally aged for 200, 400 and 500 years, artificially aged by a hydrothermal treatment (at 180, 160 or 1308C, relative air humidities of 14%, 40%, or 60% and for treatment times between 1 to 50 h), as well as reference samples, were analysed by Fourier transform infrared spec- troscopy (FTIR) attenuated total reflection (FTIR-ATR) and ultraviolet resonance Raman (UVRR) spectroscopy. Natural ageing mostly affected the hemicelluloses and lignin, as observed from the FTIR-ATR and UVRR spectra, respec- tively. The UVRR spectra of the same samples after acetone extraction indicated that lignin was partially degraded and quinone structures were possibly formed. Artificial ageing at 1608C showed a significant change in the lignin structure, a well-known effect in the thermal treatment of wood, whereas treatment at 1308C did not alter the wood structure to any significant extent. Principal component analysis of the UVRR spectra confirmed that the spectra of artificially aged wood up to 1608C are dissimilar to naturally aged wood and which are also dissimilar to unaged wood

Natural and artificial ageing of spruce wood as observed by FTIR-ATR and UVRR spectroscopy

Spruce samples, naturally aged for 200, 400 and 500years, artificially aged by a hydrothermal treatment (at 180, 160 or 130°C, relative air humidities of 14%, 40%, or 60% and for treatment times between 1 to 50h), as well as reference samples, were analysed by Fourier transform infrared spectroscopy (FTIR) attenuated total reflection (FTIR-ATR) and ultraviolet resonance Raman (UVRR) spectroscopy. Natural ageing mostly affected the hemicelluloses and lignin, as observed from the FTIR-ATR and UVRR spectra, respectively. The UVRR spectra of the same samples after acetone extraction indicated that lignin was partially degraded and quinone structures were possibly formed. Artificial ageing at 160°C showed a significant change in the lignin structure, a well-known effect in the thermal treatment of wood, whereas treatment at 130°C did not alter the wood structure to any significant extent. Principal component analysis of the UVRR spectra confirmed that the spectra of artificially aged wood up to 160°C are dissimilar to naturally aged wood and which are also dissimilar to unaged woo