Terminal group effects of DOPO-conjugated flame retardant on polyamide 6: Thermal stability, flame retardancy and mechanical performances

Jing Gao; Wentao He; Yushu Xiang; Lijuan Long; Shuhao Qin

doi:10.3389/fchem.2022.1002569

Terminal group effects of DOPO-conjugated flame retardant on polyamide 6: Thermal stability, flame retardancy and mechanical performances

Front Chem. 2022 Sep 28:10:1002569. doi: 10.3389/fchem.2022.1002569. eCollection 2022.

Authors

Jing Gao¹, Wentao He¹, Yushu Xiang², Lijuan Long², Shuhao Qin²

Affiliations

¹ Hubei Key Laboratory for Processing and Application of Catalytic Materials, Huanggang Normal University, Huangzhou, China.
² National Engineering Research Center for Compounding and Modification of Polymer Materials, Guizhou, China.

Abstract

Two DOPO-conjugated flame retardants with or without amino terminal groups (DOPO-NH₂ and DIDOPO, respectively) were synthesized and incorporated into polyamide 6 (PA6). Results demonstrated the DOPO-NH₂ endowed superior thermal, flame retardant and mechanical performances to PA6 composites. With the same loading of 15 wt%, DOPO-NH₂ can catalyze the PA6 matrix more effectively and result in more residues at high temperature. The PA6 composites containing DOPO-NH₂ exhibited higher LOI (28.0%) compared to 25.0% for the sample containing DIDOPO, and the lower heat release capacity and peak heat release rate. Furthermore, the overall mechanical properties of PA6 composites containing DOPO-NH₂ outperformed the samples containing DIDOPO, even superior to that for PA6. Such a significant difference can be mainly attributed to the existence of amino-terminal group, which can interact with carboxyl group in PA6 as confirmed by dynamic mechanical analysis, improving the compatibility between the flame retardant and PA6 matrix.

Keywords: conjugated flame retardant; flame retardancy; mechanical performance; polyamide 6; terminal group effect.