A method of improving the dispersion of graphene nanoplatelets in cellulose acetate based composite

The application of cellulose acetate (CA) in various industrial areas is strongly influenced by thermal stability. Graphene nanoplatelets (GNPs) as a highly thermal conductive filler is a promising choice to modify the stability of CA, while the practical effect falls short of the expectations associated with the promise of individually dispersed graphene owing to poor dispersion. Supercritical carbon dioxide (SC-CO2) is favorable to nanoparticles dispersion. Thus, the method, introducing SC-CO2 into the CA/GNPs system during extrusion process, was proposed to modify GNPs dispersion in CA matrix. As three main process parameters, it was researched that the effects of injection flowrate, temperature and screw rotation-rate on GNPs dispersion in CA matrix. The dispersion quality of GNPs was enhanced with the rising of injection flowrate, and the average visible GNPs count of sample G(1.25)C(0.5)T(37)R(9) decreased 74.79%, compared with sample G(1.25)C(0.1)T(37)R(9). The dispersion quality of GNPs was enhanced with the rising of temperature, and the average visible GNPs count of sample G(1.25)C(0.3)T(41)R(9) decreased 63.63%, compared with sample G(1.25)C(0.3)T(33)R(9). The dispersion quality of GNPs decreased with the rising of screw rotation-rate, and the average visible GNPs count of sample G(1.25)C(0.3)T(37)R(5) decreased 77.71%, compared with sample G(1.25)C(0.3)T(37)R(13). Thermogravimetric analysis revealed that a better GNPs dispersion is beneficial to CA stability even at an extremely low level. The maximum-weight-loss rate of the first weight-loss-stage of samples G(1.25)C(0.5)T(37)R(9), G(1.25)C(0.3)T(41)R(9) and G(1.25)C(0.3)T(37)R(5) appeared at 212, 224 and 225 degrees C, while that of samples G(1.25)C(0.1)T(37)R(9), G(1.25)C(0.3)T(33)R(9) and G(1.25)C(0.3)T(37)R(13) appeared at 207, 219 and 219 degrees C, with an increment of 5, 5 and 6 degrees C, when the content of introduced GNPs is merely 1.25 parts per thousand.