Disappearance of the filler—An interesting interfacial evolution during the photooxidative aging of polypropylene composites

The interface between the matrix and filler in polyolefin composites plays an important role in their photooxidative aging processes. An interesting phenomenon, the gradual disappearance of filler particles was observed during the early natural aging of polypropylene (PP)/CaCO₃ composites. Similar phenomena were also observed in a PP/SiO₂ composite and PP/poly(methyl methacrylate) blend. The morphological observation and tensile and chemical analyses indicated that the photooxidized groups of the PP chain interacted strongly with the filler particles; this increased the tensile strength during the early aging stage. The PP matrix was entangled in the filler particles. Therefore, the filler particles were embedded in the matrix, and the fracture occurred in the PP matrix instead of at the interface between them. On the basis of these results, a “disappearing” filler mechanism for the PP composites was proposed. This work provides a possible way for improving the mechanical properties of PP composites with appropriate aging. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42546.