Dissolution and flame retardancy of microcrystalline cellulose

Microcrystalline cellulose (MCC) was dissolved by chlorinated 1-carbamoylmethyl-3-vinyl imidazole ionic liquid ([CmVIM]Cl) and tetrabutylammonium chloride (TBAC), and then different flame retardants such as melamine phosphate (MP), ammonium polyphosphate (APP) and nano-silica (SiO2) were added to prepare flame retardant cellulose composites. The dissolution process of MCC was observed by polarizing microscope. The structure, crystallinity, thermal stability and morphology change of regenerated MCC were characterized by FTIR, XRD, TGA and SEM. The flame retardancy of cellulose composites was tested by vertical combustion test, limiting oxygen index (LOI) and thermogravimetric analysis. The results showed that the dissolution temperature was 90℃, TBAC was 8% of [CmVIM]Cl mass, the dissolution rate of MCC was up to 6.3%, and the degree of polymerization was reduced to 505. Compared with those of original MCC, the crystallinity index of regenerated MCC decreased from 74.0% to 46.4%, the initial thermal decomposition temperature decreased from 310℃ to 262℃, and the maximum weight loss rate decreased from 2.6%/min to 1.4%/min. The surface of MCC changed from smooth and flat rod structure to uneven irregular structure. The LOI of the flame retardant cellulose composites containing 5%, 10% and 10% (mass fraction) of MP, APP and SiO2 was up to 33.5%, and the vertical combustion level was Ⅴ-0. © 2021, Editorial Office of FINE CHEMICALS. All right reserved.