Abstract: In order to study the smoldering of cotton in the processing and usage state, cotton with densities of 20, 40, 60, 80 kg/m3 were selected in this paper. The bottom heating method was used to carry out the experimental study. The effect of density on smoldering characteristics and residues was analyzed. The results show that with the increase of density, the porosity and air permeability coefficient of the sample change, so that the critical smoldering temperature increase by about 35 ℃, the spreading rate decrease by 50%～60%, and the smoldering duration increase from 2 500 s to 5 000 s. After smoldering, the shrinkage degree decreases and the collapse degree increases. The smoldering residue is a black flocculent covering the inner gray ash, and the ash volume increases with increasing density. The results can provide reference for the prevention and investigation of cotton smoldering fire.

Key words: cotton, smoldering, combustion residue, thermogravimetric analysis, critical smoldering temperature