Environmentally friendly adhesives derived from glycerol-based polymers

Biodegradable, renewable, and environmentally friendly glycerol-based wood adhesives were synthesized through polycondensation reaction between dicarboxylic acids (sebacic and citric acid) and glycerol using different molar ratios, i.e. poly(glycerol sebacate) - PGS, poly(glycerol citrate-co-sebacate) - PGCS, and poly(glycerol citrate) - PGC. Thermal properties of the synthesized polymers were evaluated after cross-linking. Results showed that thermal stability was influenced by polymer molecular structure, being lower for PGC due to the presence of quaternary carbons of citric acid. Differential scanning calorimetry analyses showed an intermediate glass transition for the copolymer in comparison with homopolymers. Tensile shear strength tests showed that the presence of citric acid in the polymer improves adhesion and reduces adhesive flexibility, contrary to what happens to polymers with sebacic acid. This behavior was also proved through morphological analyses of the fracture surface. Adhesives with tailor-made properties were produced from glycerol, opening up new revenues for a by-product of the biodiesel production chain.