Abstract
Summary: In order to achieve better mechanical properties, most work on polymer/fiber composites has been focused on the importance of the chemistry used to modify the surface of the fibers and improving the adhesion between the fiber and the matrix using coupling agents. Our purpose in this study was to determine the effect of shear on the fiber orientation and interfacial adhesion in poly(propylene)/glass fiber composites via dynamic packing injection molding (DPIM), in which the melt is first injected into the mold and then forced to move repeatedly in a chamber by two pistons that move reversibly with the same frequency as the solidification progressively occurs from the mold wall to the molding core part. SEM, TGA, FTβIR, AFM and mechanical testing were used to characterize the samples obtained. The majority of fibers are aligned parallel to the flow direction along the sample thickness, even at the core, in contrast to the products obtained via conventional injection molding where the orientation of fibers is observed only at the skin. More importantly, we found that shear could enhance not only the fiber orientation, but also the interfacial adhesion between the fibers and the matrix, particularly for samples with higher fiber contents, resulting in an obvious increase in tensile strength and the onset degradation temperature. A possible transcrystallization was evidenced by AFM investigations of the dynamic packing injection molded samples, which is worth further study.
SEM micrographs representing the glass fiber after PP in the composites was extracted (GF30, dynamic sample).
magnified imageSEM micrographs representing the glass fiber after PP in the composites was extracted (GF30, dynamic sample).