Investigation of interfacial adhesion of telechelic polypropylenes for carbon fiber-reinforced plastics

The interfacial adhesion property of telechelic polypropylenes (PPs) imparted by the controlled thermal degradation of commercial PPs and the subsequent end group transformation was investigated to determine the potential of telechelic PP as a candidate for PP matrix resin-coupling agents for CF-reinforced PP composites. In particular, we studied the interfacial shear strength (IFSS) between telechelic PPs with terminal double bonds or terminal hydroxyl groups and CFs for the first time. The hydroxyl-terminated PP showed higher IFSS than that of commercial PPs. The hydroxyl groups of hydroxyl-terminated PP interacted with CF surfaces via hydrogen bonding, which led to higher interfacial adhesion. Furthermore, hydroxyl-terminated PP homopolymer (hPP-OH_27k) was mixed with conventional isotactic polypropylene (iPP), and used as a coupling agent. The IFSS of the iPP/hPP-OH_27k blend was comparable to that of iPP/maleic anhydride-grafted polypropylene (MAPP), which is typically used as a coupling agent of the PP matrix. The iPP/hPP-OH_27k blend showed higher crystallinity and higher tensile strength than the iPP/MAPP blend based on the DSC measurements and tensile tests. These results indicated that hPP-OH_27k functions as a novel coupling agent of the PP matrix.