For high toughness, the
fracture energy must be at least equal to or larger than the surface
energy at the interface of cracking. The composites with diisocyanates
had higher fracture energy than the composite without
diisocyanates, This indicated that the reaction of isocyanate groups
and carboxyl and hydroxyl groups occurred, which resulted in
chemical bonds between the surface of ramie and PLA, leading to
high interface adhesion