Cost-Effective and Fully Biodegradable PBAT Composites: Integrating Natural Fillers and Chemical Foaming Techniques

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.