Grafting hyperbranched polyamide onto polyvinyl alcohol fibers to reinforce thermoplastic starch and other biodegradable plastics.

Polyvinyl alcohol fiber (PVAF)‐reinforced thermoplastic starch (TPS) is a sustainable alternative to petroleum‐based plastics; however, the mechanical performance of PVAF‐TPS is limited owing to its weak interfacial interactions. In this study, we prepare hyperbranched polyamide‐grafted PVAF (H‐PVAF) via a two‐step acylation reaction with succinic anhydride and iminodiacetic acid. The optimal temperature (40 ~ 70°C) and time (0 ~ 2 h) of the acylation reactions are determined using a central composite rotatable design. The effects of the reaction time and temperature on the interfacial shear properties of H‐PVAFs in the TPS matrix are determined using pull‐out tests. Additionally, Fourier‐transform infrared, x‐ray diffraction spectroscopy, scanning electron microscopy, and thermogravimetry are used to analyze the molecular structure, surface morphology, and thermal properties. H‐PVAFs in TPS matrices exhibit significant enhancements in maximum load, interfacial shear strength, and pull‐out energy. In particular, the H‐PVAF reacted at 55°C for 0.08 h exhibited a maximum load, interfacial shear strength, and pull‐out energy of 43cN, 0.805 MPa, and 174.5 J/mm2 respectively. Finite element analysis further confirmed the improvement in the interfacial behavior of H‐PVAF in TPS. Finally, the grafted fibers are compatible with other biodegradable polymer matrices. Therefore, reinforcing TPS with H‐PVAF is a promising strategy for enhancing the performance of TPS‐based and other degradable plastics in various applications such as disposable tableware, agricultural mulching films, and biomedical applications. Highlights: Hyperbranched polymers were formed to create a "tree‐root like" biomimetic surface on PVAFs.A two‐step acylation reaction grafts hyperbranched polymers on PVAFs.Finite element simulation confirmed the improvement in the fiber/matrix interface. [ABSTRACT FROM AUTHOR]