Preparation and Characterization of Cyclodextrin Coated Red Phosphorus Double-Shell Microcapsules and Its Application in Flame Retardant Polyamide6

Using the melamine borate and crosslinked beta-cyclodextrin as shell materials, the double-shell microcapsules (Mic-DP) of red phosphorus (RP) was prepared, and its flame-retardant effect on polyamide 6 (PA6) was investigated. Compared with RP, Mic-DP showed lower hygroscopic and better inoxidizability. The limiting oxygen index (LOI) of PA6/13%Mic-DP was 27.8%, and PA6/13%Mic-DP reached V-0 rating. After the addition of 13% Mic-DP, the total exothermic (THR), peak exothermic (PK-HRR), and average effective thermal combustion (AV-EHC) rates of PA6 decreased. In addition, in order to investigate its flame-retardant mechanism, the pyrolysis gas chromatography-mass spectrometry (Py-GC-MS), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) methods were used, and the results showed that mic DP acted as a flame retardant in the gas and condensed phases. The Mic-DP exhibited good compatibility and dispersibility in PA6.

Automated summary

The double-shell microcapsules (Mic-DP) of red phosphorus (RP) were prepared using melamine borate and crosslinked beta-cyclodextrin as shell materials, and their flame-retardant effect on polyamide 6 (PA6) was investigated. Mic-DP showed lower hygroscopicity and better inoxidizability compared to RP. The addition of Mic-DP decreased the thermal combustion rates of PA6. Py-GC-MS, SEM, and FT-IR analyses confirmed that Mic-DP acted as a flame retardant in both gas and condensed phases.