Effect of adding two kinds of acid‐terminated polypropylene and surface modification using tannic acid‐iron ion complex on the mechanical properties of carbon fiber/polypropylene composites

Abstract This study investigated the effect of maleic anhydride‐terminated polypropylene (PPtMA) or polyacrylic acid‐terminated polypropylene (PPtAA) addition and surface modification of carbon fibers (CFs) with a tannic acid (TA)‐Fe³⁺ complex on the mechanical properties of CF/polypropylene (PP) composites. The addition of PPtMA or PPtAA improved the mechanical properties. Examining the effects of the amount of PPtMA and PPtAA added (compared at 5 and 20 wt% in PP) revealed that the amount that resulted in good mechanical properties was different for PPtMA and PPtAA (PPtMA: 5 wt% in PP, PPtAA: 20 wt% in PP). The TA‐Fe³⁺ coating further enhanced these improvements. Scanning electron microscopic analysis revealed that the addition of compatibilizers improved interfacial adhesion. In addition, the combined use of compatibilizers and CFs coated with the TA‐Fe³⁺ complex showed particularly strong effects. Analysis by differential scanning calorimetry showed that adding a large amount of compatibilizer reduced the crystallinity; however, in the case of PPtAA, hydrogen bonding enhanced the rigidity of the matrix resin and improved the interfacial adhesion. Therefore, even at high PPtAA concentrations, the CF/PP composite containing CFs coated with the TA‐Fe³⁺ complex maintained good mechanical properties. Highlights Carbon fiber/polypropylene composites were prepared with compatibilizers. Compatibilizers were PP terminated with maleic anhydride or polyacrylic acid. The addition of either compatibilizer resulted in good mechanical properties. The surface of CFs was also modified with a tannic acid (TA)‐Fe³⁺ complex. The compatibilizer + complex‐modified CFs improved interfacial adhesion.