4. NIPU adhesives for wood

4.1 Lignin-based NIPU adhesives

Lignin is one of the main components of wood, and the second most abundant natural polymer. However, lignin is a complex natural copolymer whose composition varies from one tree species to another, and whose structure differs according to the environment, making it difficult to study. Lignin makes up around 24-33% of woody substance in softwoods and 16-24% in hardwoods, respectively.

Despite the wide availability of this raw material, little use is made of it due to its complex structure, low reactivity and major chemical differences depending on the source. Most lignin is used as fuel.

Lignin is considered a waste product, or by-product, of the pulp industry, with production of around 80 to 100 million...