Improved self-healing properties of collagen using polyurethane microcapsules containing reactive diisocyanate

Collagen is a natural polymer much available as a waste material. However, a more extensive use of collagen as an engineering material is restricted due to its low mechanical strength. This work presents a collagen-microcapsules system and evaluates the hypothesis that a self-healing ability can be imposed on a collagen matrix to improve its tensile strength. Collagen films containing various types of microcapsules were studied using tensile tests (TTs). To evaluate the self-repairing capacity of the developed system, samples were submitted to a 20% strain (to develop micro-cracks in the material that could lead to the rupture of microcapsules and release of diisocyanate) and then left to stand for 20 min. A new TT was performed, named paused tensile test (PTT). The samples of pure collagen underwent no alteration with respect to their mechanical properties comparing TT and PTT results. In contrast, some samples containing microcapsules presented an increase of around 70% in mechanical strength when compared with the pure collagen results, proving that the released diisocyanates were effective in reacting with collagen and improving its mechanical strength. This type of behavior and the observed enhanced property can extend the usage of collagen to a variety of engineering applications. (C) 2016 Society of Chemical Industry