Structural modification and characterization of lignosulfonate by a reaction in an alkaline medium for its incorporation into phenolic resins

Abstract

ABSTRACT:We studied the enhancement of lignin reactivity in an alkaline medium, using sodium hydroxide in a microreactor set. The chemical composition and structural characterization of the reacted lignosulfonate in terms of the phenolic hydroxyl groups, aromatic protons, weight-average molecular weight, number-average molecular weight, and lignosulfonate content of all reacted lignins were determined. The techniques that we used were ultraviolet spectroscopy, proton nuclear magnetic resonance spectroscopy, and aqueous gel permeation chromatography. Using response surface methodology, we studied how the temperature and reaction time affected the lignin properties. The reaction conditions were temperatures between 116 and 1808C and reaction times between 18 and 103 min. Modeled response surfaces showed that the two factors affected the lignin properties within the studied ranges. The phenolic hydroxyl groups, aromatic protons, and lignosulfonate content increased when the severity of the treatment increased. The weight-average molecular weight, number-average molecular weight, and solid yield (%) decreased when the severity of the treatment increased. The reactivity of the modified lignins was studied with a formaldehyde reactivity test: more severe conditions produced greater improvements in the formaldehyde reactivity.

Characterization of Thermal and Mechanical Properties of Lignosulfonate- and Hydrolyzed Lignosulfonate-based Polyurethane Foams

“…These changes indicate an increase in hydroxymethyl group abundance and ether bond scission resulting from the alkaline hydrolysis of lignin (El Mansouri et al 2006). Wysocka et al (2016).…”

“…Alkaline hydrolysis of lignin was performed in a 100-mL pressurized reactor (Parr Instruments, Moline, IL, USA), according to the procedure described by El Mansouri et al (2006) at 170 °C for 2 h.…”

Production and Application of Lignosulfonates and Sulfonated Lignin

“…[83] Scheme 6d epicts the alkaline hydrolysis and purification of lignosulfonates. Alkalineh ydrolysish as been proposed to increase the reactivity of lignosulfonates.…”

Management of Corn Stalk Waste as Reinforcement for Polypropylene Injection Moulded Composites

“…Therefore, lignin becomes more reactive toward the esterification reaction or hydrogen bonding at the interface. The appearance of new hydroxyl groups after alkaline treatment of lignocellulosic materials in lignin molecules is due to the cleavage of ether bonds, such as α and β-O-4, which are the major linkages in a lignin molecule (El Mansouri et al 2006). The second theory is related to substantial modification of the chemical composition of the fiber, thus affecting the intrinsic mechanical properties of the reinforcing fibers.…”