Organic Aluminum Hypophosphite/Graphitic Carbon Nitride Hybrids as Halogen-Free Flame Retardants for Polyamide 6

Chengxin Guo; Yongshuai Zhao; Guichen Ji; Chaosheng Wang; Zhihan Peng

doi:10.3390/polym12102323

Organic Aluminum Hypophosphite/Graphitic Carbon Nitride Hybrids as Halogen-Free Flame Retardants for Polyamide 6

Polymers (Basel). 2020 Oct 11;12(10):2323. doi: 10.3390/polym12102323.

Authors

Chengxin Guo¹, Yongshuai Zhao¹, Guichen Ji¹, Chaosheng Wang¹, Zhihan Peng¹

Affiliation

¹ State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China.

Abstract

The novel organic aluminum hypophosphite (ALCPA) and its hybrid (CNALCPA) with graphitic carbon nitride (g-C₃N₄) were successfully synthesized and applied as halogen-free flame retardants in polyamide 6 (PA6). Their structures, morphology, thermal stability, and fire properties were characterized. Results showed that both ALCPA and CNALCPA had good flame retardancy. PA6/CNALCPA composites achieved a high limited-oxygen-index (LOI) value of 38.3% and a V-0 rating for UL94 at 20 wt % loading, while PA6/ALCPA composites could reach a V-1 rating for UL94. The flame-retardant mechanism was also studied. On the one hand, the incorporation of g-C₃N₄ produced more gas-phase products, which indicated a gas-phase mechanism. On the other hand, g-C₃N₄ could catalyze the thermal degradation of ALCPA and PA6 to form a compact char layer that was evidence for a solid-phase mechanism. The tensile test of the PA6 composites also displayed good mechanical properties.

Keywords: flame retardancy; graphitic carbon nitride; halogen-free; organic aluminum hypophosphite; polyamide 6.