2022 Volume 71 Issue 5 Pages 432-438
One of the molding methods for the glass fiber reinforced thermoplastics (GFRTP) is press and injection hybrid molding, in which GFRTP is pre-heated and press-molded into a mold and the thermoplastic is injection-molded on the surface of the GFRTP. Since the press and injection hybrid molded product is easily fractured at the interface between GFRTP and the injection material, several methods have been proposed for improving the interface. From the viewpoint of interfacial bonding between GFRTP and injection thermoplastic, however, the reported methods are composed of the same kind of resin, so it is difficult to have both the high interfacial bonding strength between GFRTP and injection resin, and the high mechanical properties of GFRTP, when polypropylene (PP) is used for injection resin. In this study, we evaluated the mechanical properties of matrix-hybrid GFRTP, which has been developed by stacking the outer layer consisting of PP or PP with maleic anhydride modified PP (M-PP) and the inner layer of PA6. Furthermore, tensile test at the rib root of press and injection hybrid molded product using PP as the injection material was also conducted to clarify the effect of matrix hybridization on the interfacial bonding strength at the rib root. The matrix hybrid GFRTP using M-PP and PA6 showed 2.5 times higher in bending strength as compared to the GFRTP which is only composed of M-PP as the matrix resin. In addition, from tensile tests at the rib root of a press and injection hybrid molded product using PP as an injection resin, the matrix hybrid GFRTP exhibited higher interfacial bonding strength than the single resin GFRTP. These results indicated that the press and injection hybrid molded product with high interfacial bonding strength at the rib root and high mechanical properties can be obtained by using the matrix hybrid GFRTP composed of M-PP, which is the same type as the injection PP on the outer layer and PA6 with GFRTP exhibiting high strength on the inner layer as the shell structure.
