CO₂-Sourced Poly(chloropropylene carbonate) with High Flame-Retardant Performance

The alternating copolymer of CO₂ with epoxide is a green plastic that can efficiently transform CO₂ into valuable chemicals. Despite the significant advances made, the restricted practical application of CO₂-sourced polycarbonates due to their lack of functionality has hindered field development. We successfully demonstrated the flame retardancy of poly(chloropropylene carbonate) (PCPC), a perfectly alternating copolymer of epichlorohydrin (ECH) and CO₂. This was prepared at a 200-gram scale using a high-efficacy tetranuclear organoborane catalyst. PCPC’s excellent flame-retardant performance has been proven by both the vertical combustion test (UL94 V-0) and the limiting oxygen index (LOI) value (29.1%). The underlaid flame-retardant mechanism of PCPC was clearly elucidated. As a result, we confirmed that the generated cyclic carbonates and concurrently released flame-retardant chlorine radicals, hydrogen chloride, and CO₂ during combustion render PCPC an excellent flame retardant. Furthermore, we investigated the practicability of PCPC as a halogen-rich polymeric flame retardant by blending it with commercial bisphenol A polycarbonate (BPA-PC). PCPC upgraded the flame retardancy rating of BPA polycarbonate from V-2 to V-0 even with a mere 1 wt% addition. It is our hope that this result will prove useful in future developments of advanced CO₂-sourced polymeric materials.