Construction of sustainable polyurethane-based gel-coats containing poly (ε-caprolactone)-grafted lignin and their coating performance

In order to use a lignin as a polyol in polyurethane-based gel-coated films, poly(ε-caprolactone) grafted lignin (PCL-g-lignin) was synthesized by a ring-opening polymerization of ε-caprolactone in presence of a pristine lignin. This reaction was confirmed by FT-IR spectroscopy. By usage of the PCL-g-lignin, polyurethane-based gel-coated films was prepared through a simple urethane reaction following which the effects of the PCL-g-lignin content on the physical properties and surface characteristics of the polyurethane-based gel-coat films was examined. With increased PCL-g-lignin content, the decreased cross-linking density resulted in the reduction of physical properties such as the tensile strength and surface hardness of the gel-coated films. Their surface characteristics (e.g., adhesion strength, abrasion, and gloss) were constant, regardless of the PCL-g-lignin content increase in the gel-coated films.