Study on properties and application of pyrophosphate flame retardant microcapsules prepared from hemicellulose maleate

The paper presents a new, non-pollution pyrophosphate flame retardant microcapsules which was prepared by in situ polymerization with hemicellulose maleate (HCMA), urea, formaldehyde and pyrophosphate. The HCMA was obtained through the hemicellulose extracted from the waste liquid of regenerated cellulose fiber and modified by maleic anhydride. The pyrophosphate flame retardant microcapsules were degradable and environment friendly, and they could effectively provide compatibility with matrix and flame resistance. The preparation and properties of flame retardant microcapsules were determined. Under the preparation conditions of which the core–shell ratio was 2:1.5 (mol:mol), pH was 3.5 and temperature was 55 °C, the embedding quantity reached to 66.7%, and the average particle size of flame retardant microcapsules was about 20 μm. The flame retardant microcapsules exhibited good thermal stability. Thermal kinetics analysis was studied based on the Coats–Redfern equation, and the changes of activation energy during the thermal degradation were determined. The pyrophosphate flame retardant microcapsules were added into the regenerated cellulose fiber stock solution to prepare the film sample. By adding 15% flame retardant microcapsules, the LOI of film sample reached 29.1%, and the UL-94 on vertical combustion could reach UL-94-V-0. The film sample with pyrophosphate flame retardant microcapsules showed excellent flame retardant performance. The preparation on shell of flame retardant microcapsules