Seeking a facile strategy to synthesize efficient and inexpensive flame retardant which endows biobased polyamide 56 (PA56) with desirable flame retardancy is an urgent need. Here, ammonium polyphosphate (APP) was modified with graphitic carbon nitride (g-C 3 N 4 ) to synthesize a nitrogen-phosphorus flame retardant (CN@APP) and then applied in biobased PA56. The X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectra demonstrated that APP was successfully microencapsulated with g-C 3 N 4 . The micromorphology structure was further characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). PA56/CN@APP attained a UL 94 V-0 rating and limiting oxygen index (LOI) value of 31.7%. A sharp reduction of 35.3% in peak heat release rate (pHRR) and 24.0% in total heat release (THR) and an 874% increase in char yield were noticed for PA56/CN@APP2 compared with pure PA56. Additionally, the peak smoke production rate (pSPR) and total smoke production (TSP) of PA56/CN@APP2 were 33.0% and 21.8% lower than those of pure PA56. Scanning electron microscopy (SEM), time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy were employed to analyze the condensed phase residues from the cone calorimeter test (CCT). The results indicated that CN@APP was beneficial for forming a more stable and compact carbon layer during combustion, thereby insulating the heat transfer and improving the flame retardancy and smoke suppression of PA56.

Biodegradable poly(butylene adipate‐co‐terephthalate) (PBAT) has excellent processing and mechanical properties. However, PBAT is expensive and its relatively slow biodegradation rate limits its wide application. In this paper, PBAT/thermoplastic starch (TPS) complexes were prepared by a two‐step process using epoxidized soybean oil (ESO) as a reactive compatibilizer. The compatibilizing ability of ESO was investigated by FT‐IR and GPC. Results showed ESO could form a chemical bonding interface with PBAT and TPS. Compared to PBAT/TPS, tensile strength, elongation at break and tear strength of PBAT/TPS/5%ESO composites increased by 84%, 53%, and 68%, respectively. The optical transparency of the PBAT/TPS/5%ESO film improved by 6% compared to the PABT/TPS film. This research offers a viable solution for the preparation of high performance, green PBAT/TPS complexes.