Synergistic potentiation of foaming ability and flame retardancy in biodegradable poly (butylene adipate-co-terephthalate)/bamboo powder composites via aluminum hypophosphite

The use of supercritical carbon dioxide (scCO 2 ) foaming without waste emissions is a new trend in preparing lightweight foams and is also suitable for degradable polymers such as poly(butylene adipate-co-terephthalate) (PBAT). However, the flammable nature of the foam limits its application. In this study, bamboo powder (BP) was used as the framework structure to inhibit the shrinkage of PBAT foams, and aluminum hypophosphite (AHP) was used as a flame retardant to explore the influence of the addition amount of AHP on the properties of the PBAT/BP foams. When the additional 30 wt% AHP was added, the PBAT/BP foam achieved a good balance between flame retardancy and foaming performance. The vertical burning test (UL-94) rating reached V-0 and the limiting oxygen index (LOI) was 25.8%. The expansion ratio of the foam was 10.4 with a uniform microcellular structure size of 60.01 μm. The cell density was 2.49 × 10 7 cells/cm 3 . AHP was found to facilitate bubble nucleation and form a protective char layer, contributing to both improved foaming and flame inhibition. When the addition amount of AHP increased, the foaming performance and compression rebound performance were compromised. This research provided a solution for the production of PBAT/BP biodegradable foams with excellent flame retardant and foaming properties.