Cost‐Effective and Fully Biodegradable <scp>PBAT</scp> Composites: Integrating Natural Fillers and Chemical Foaming Techniques

ABSTRACT Polybutylene adipate‐co‐terephthalate (PBAT) is a promising biodegradable polymer, but its high cost limits wider use. This study integrates low‐cost bamboo powder (BP) and chemical foaming injection molding to produce economical PBAT‐based composites. A compatibilizer, PBAT‐g‐MAH, was produced via melt free‐radical grafting. The influence of BP and PBAT‐g‐MAH on the mechanical, rheological, thermal, and foaming properties of PBAT composites was systematically investigated. Due to poor PBAT/BP compatibility, composites initially showed decreased mechanical, rheological, thermal, and foaming properties. At 30 wt.% BP, tensile strength decreased by 30.5% (from 23.24 to 16.16 MPa), whereas elongation at break declined by 45.3% (from 1243.5 to 679.8%). Foam morphology also deteriorated: the mean cell size increased from 32 to 58 μm, cell density dropped from 5.1 × 10 6 to 1.0 × 10 6 cells/cm 2 , and cell distribution became nonuniform. In contrast, the introduction of PBAT‐g‐MAH significantly improved interfacial interactions between BP and PBAT, leading to enhanced filler dispersion and the restoration of overall composite properties. PBAT/BP/PBAT‐g‐MAH composites showed performance comparable to neat PBAT, demonstrating that lightweight, biodegradable PBAT‐based products can be fabricated while maintaining key properties by integrating natural fillers with compatibilization strategies and chemical foaming injection molding techniques.