The Influence of the Content of Polybutylene Adipate‐Co‐Butylene Terephthalate‐Based Polyurethane Prepolymer on the Structure and Properties of PBAT ‐Based Composite Materials

Abstract

Polybutylene adipate‐co‐terephthalate (PBAT) is a biodegradable copolyester with good toughness but low strength and high cost. To address these issues, inexpensive bagasse is used as filler and Polybutylene adipate glycol‐based polyurethane prepolymer (PBAPU) as compatibilizer to prepare biodegradable composites. A novel “many‐to‐many” reactive compatibilization and toughening mechanism is proposed. Under the dual action of chemical crosslinking and physical entanglement, interfacial bonding is enhanced, improving composite performance. Results show that as PBAPU content increases from 0 to 20 phr, elongation at break increases from 6.2% to 100.0% (over 15‐fold), and impact strength increases from 4.48 to 33.10 kJ/m 2 (approximately 6.4‐fold). SEM images confirm improved interfacial compatibility and thermal gravimetric analysis results show enhanced thermal stability. Although higher PBAPU contents further improve elongation at break and impact strength, they are accompanied by a reduction in Young's modulus. Considering the overall balance between tensile strength, toughness, stiffness, and the practical use of compatibilizers, 10 phr PBAPU was considered to provide a balanced formulation. The PBAPU mechanism involves: flexible polyester chains physically entangling with PBAT, while terminal –NCO groups chemically react with hydroxyl groups to form stable bonds. This synergistic effect is the fundamental reason for performance enhancement.