A novel conjugated microporous polymer nano hollow sphere containing N, P and Si flame retardant elements with both thermal insulation and flame retardant properties

It is particularly important to develop new materials with both thermal insulation and flame retardant properties for addressing the severe issues caused by fire accidents. Herein, a kind of conjugated microporous polymer nanospheres with hollow structure (HCMPNS) was synthesized by Sonogashira-Hagihara cross-coupling reaction using SiO2 nanospheres as hard template and 1,3,5-triacetylenebenzene, as alkynyl monomer. Then, HCMPNS was chemically graft-modified with azidotrimethylsilane (TMSA) by "click" chemistry (HCMPNS-FRSi), and the HCMPNS-FRSi obtained from the reaction was introduced into flammable epoxy resin (EP) to obtain EP based composites, i.e. EP-I and EP-II. The thermal conductivities were found to be 0.0341 W m- 1 K- 1 and 0.0268 W m-1 K- 1 for EP-I and EP-II, respectively, showing excellent thermal insulation performance. The total heat release (THR), the total smoke production (TSP) and the peak CO2 produced (CO2P) of EP-I were reduced by 18.0 %, 8.0 %, 14.3 % compared with pure EP as measured by cone calorimetry (CC), respectively, indicating a certain extent flame retardant effect. In order to further improve its flame retardant properties, phosphoric acid containing the flame retardant phosphorus element was added to HCMPNS-FRSi (HCMPNS-FRSi-P), followed by the introduction of the resulting HCMPNS-FRSi-P into EP matrix to form EP based composites with Si and P dual incorporation (EP-III and EP-IV), with the thermal conductivities of 0.0470 W m- 1 K- 1 and 0.0855 W m-1 K-1,respectively. Through the cone calorimetry (CC) of EP-III, EP-IV, total heat release (THR) were reduced by 17.0 %, 23.8 %, total smoke production (TSP) were reduced by 6.2 %, 7.2 %, respectively. The peak heat release rate (HRR) and the peak CO2 produced (CO2P) of EP-IV were reduced by 16 % and 25 %, respectively, compared with pure EP. It has good thermal insulation and flame retardant effect. Therefore, HCMPNS-FRSi-P, as a new type of flame retardant material, has great potential in the fields of electronics, construction, transportation and so on.