Preparation of DOPO coated conjugated microporous polymer hollow nanospheres with excellent flame retardancy and thermal insulation

Materials with thermal insulation and flame retardant properties are highly sought after in construction industry. In this study, two hollow-structured conjugated microporous polymer spheres (HCMPs) were successfully synthesized via the template method by polymerizing 1,3,5-triethynylbenzene with 3-amino-2,6-dibromopyridine and 2-amino-3,5-dibromopyridine respectively. To enhance flame retardant properties, HCMPs were impregnated with ethanol-soluble 6 H-dibenzo (C, E) (1,2) phosphine oxide-6-oxide (DOPO) (named as HCMP-FR), which maintains a hollow structure, enabling it to serve as a heat insulator, as observed under transmission electron microscope (TEM). The two types of HCMP-FR with a thermal conductivity of 0.047 W m-1 K-1 and 0.051 W m-1 K-1 respectively, exhibit excellent thermal insulation property. HCMP-FRs were added in to epoxy resin (EP) composites to further investigate the property of it. Under addition of 1.3%wt HCMP1-FR and HCMP2FR, the thermal conductivity of EP composites (0.159 W m-1 K-1 and 0.146 W m-1 K-1) decreased by 25.3% and 31.4% compared with pure EP composites respectively, and the density (0.651 g cm-3 and 0.8 g cm-3) decreased by 42.1% and 22.5%, significantly reducing EP's thermal conductivity and density. The cone calorimeter (CC) tests show that the pHRR of EP composites at 0.6%wt addition was 859.04 kW m- 2 and 904.35 kW m- 2, respectively, which were 17.5% and 13.1% lower than that of pure EP, and the TSP decreased by 44.9% and 41.3% when 1.3% HCMP-FRs was added, which shows an excellent smoke depressing property. Therefore, the HCMP-FRs synthesized have highly promising for application in thermal insulation and flame retardancy of energy saving building.