Visualization and Quantification of Interface Structure in Injection‐Molded Glass Fiber Reinforced Polypropylene

ABSTRACT In light of global regulations on greenhouse gas emissions, there is a pressing need for the automotive industry to reduce vehicle weight. This requires the efficient development of high‐performance materials, in particular, high‐performance composite materials consisting of resins, inorganic fillers, and other additives that can be thinned. Expanding the range of applications of composite materials in place of inorganic materials is also an effective way to reduce vehicle weight. In order to realize high‐performance composite materials, it is important to elucidate the interfacial adhesion mechanism between resin and reinforcement, which greatly influences the mechanical properties of composite materials. In this study, we visualized the interface structure of glass fiber reinforced polypropylene with or without maleic anhydride‐modified polypropylene (MAPP) in three dimensions. Quantitative evaluation of the interface structure by image analysis was performed, which showed its positive correlation between the evaluation result and the fiber/resin interfacial shear strength as determined by the pushout test on an SEM nanoindenter. The results suggest that an MAPP‐rich interface exists around the glass fiber and that the interface structure changes depending on the amount of MAPP added. It was also confirmed that the MAPP content affects the tensile strength of the composite materials.