Flame-retardant phytic acid-decorated thermoplastic starch/halloysite nanotube composite films with enhanced mechanical strength and excellent barrier properties.

Thermoplastic starch (TPS), a green and fully biodegradable composite, is considered the most viable option for replacing petroleum-based polymers. However, the poor mechanical properties, high flammability and moisture absorption susceptibility of TPS severely restrict its large-scale applications. Through PA phosphorylation and blending with halloysite nanotubes (HNTs), phytic acid (PA)-phosphorylated HNT/TPS composite films (HNTPSFs) were fabricated with enhanced mechanical strength, excellent flame retardancy, and improved barrier properties. The introduction of HNTs substantially increased the mechanical properties (tensile strength increased 54.3 % and elongation at break decreased 37.0 %) of TPS films and reduced the diffusion of water vapor (decreased 34.1 %). Thermogravimetric analysis studies demonstrated that the HNTPSFs had exceptional thermal stability at their anticipated working temperatures. Furthermore, when the PA content in the composite films increased, the peak heat release rate, total heat release and fire growth index of the HNTPSFs all decreased substantially, demonstrating the improved flame retardancy of HNTPSFs. Hence, the synthesized fully biodegradable TPS composites show enormous potential in the field of renewable biopolymers.