Highly transparent and fire-safe polypropylene carbonate composites via guanidine phosphate hydrogen bonding complexation

It is a challenge all the time to prepare transparent flame retardant polymer composites. In this contribution, a biodegradable carbon dioxide derived copolymer polypropylene carbonate (PPC) has been chosen considering its signality for human environmental protection. Nevertheless, the low glass transition temperature (Tg) of PPC limits its practical applications. Herein, polylactic acid (PLA) and flame retardant guanidine phosphate (GP) were selected to obtain PPC composites by the interaction of intermolecular hydrogen bonds (H-bonds). The properties of PPC/PLA/GP composites were systematically studied. The test results showed that GP can be uniformly dispersed and contributed to the composites with enhanced Tg and flame-retardant properties. As a model system, 3 wt.% of GP enabled the PPC/PLA/GP-3 composites with Tg of 60.0 ℃, UL-94 grade of V-0, limiting oxygen index (LOI) of 30.8 %, and a significant reduction of THR (13 %), pHRR (32 %), and pCO (84 %), respectively. Besides that, the introduction of GP displayed slight influences on the intrinsic transparency nature of PPC/PLA. This study provided a facile approach for solving the bottleneck of PPC for advanced applications.