The extraction of polyol for the synthesis of lignin-based polyurethane coatings – a review

ABSTRACT

Lignin, with its availability, aromatic structure, and abundant hydroxyl groups, presents a promising source of green bio-based polyols. The environmental implications of oil-derived polymeric materials have sparked interest in renewable biopolymers and composites from natural sources, including polyurethane composites. This review investigates optimal methods for lignin extraction for use in lignin-based polyurethane coatings, scrutinizes alternatives to oil-based polyols, compares existing chemical modification methods of lignin for use in polyurethane coatings and resins, and discusses the control of synthesis and final properties of lignin-based polyurethane, emphasizing the crucial role of the stoichiometric ratio of NCO groups in the isocyanate to the total OH groups in a lignin-based polyol. While numerous studies have focused on polyurethanes with and without isocyanate, this review describes the synthesis of lignin into bio-polyols and its potential as a substitute for petroleum-based polyols, highlighting organosolv and Kraft lignin as optimal choices for replacing oil-based polyols in polyurethanes due to their high purity.

KEYWORDS:

• Non-isocyanate polyurethane
• coatings
• wood

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors received specific funding for this study from Tarbiat Modares University of Tehran, Iran.