Highly rigid, fire-resistant, and sustainable polybutylene adipate terephthalate/polybutylene succinate composites reinforced with surface-treated coffee husks

Despite the increasing demand for eco-friendly polymer materials that can be employed in advanced industrial applications, the development of biodegradable polymer composites with advantageous mechanical properties and fire resistance remains a challenge. In this work, we fabricated fully biodegradable polybutylene adipate terephthalate (PBAT)/polybutylene succinate (PBS) composites reinforced with surface-treated coffee husks (CHs) with high rigidity, mechanical strength, and fire resistance. CH characterization confirmed that the surface was successfully treated with different C4 dicarboxylic acids. Morphological analysis of the composites revealed that the surface-treated CHs helped to improve both the compatibility between the matrices and the interfacial interaction between the filler and the matrices. The tensile strength and modulus of the composites increased by 96% and 278% compared to neat PBAT. Flammability and combustion tests confirmed that the combined effect of phosphorus and dicarboxylic acid surface treatment improved the fire-resistant behavior of the composites. This study thus presents a promising technique for the development of PBAT composites with suitable mechanical properties and fire resistance.