Comparison between Fig. 4 and 5 it is observed that non-coupled composite samples had a weak
interfacial region and damage mainly occurred along the loose and weak interface between the wood flour
and PP matrix under loading. However, with the MAPP coupled composites, the wood flour is combined
with the PP matrix through the covalent bonding or strong interfacial bonding, and interfacial fracture
usually accompanied with a cross section damage of the wood flour. Hence, after the failure, the flour
surface in the untreated composites is smooth; whereas the wood flour in the MAPP treated composites has a
rough surface. It is embedded in the matrix with a chemical link