Due to the low-cost, earth-abundant
availability and eco-friendly characteristics, cellulose derivatives (CDs)
are being increasingly used as co-binders in the production of pigment coatings. In the present work, a comparative study on the effect of nanocrystalline cellulose (NCC) and sodium carboxymethyl cellulose (CMC) on the colloidal stability and rheological properties of pigment coatings was carried
out. The sedimentation stability assessment results
indicated that NCC replacing CMC significantly improved the colloidal stability of pigment coatings. In the presence of NCC, the resulting coatings showed no indication of sedimentation within a 48-hour storage period. Moreover, the rheological measurements revealed that all pigment coatings exhibited a strong shear-thinning behavior as the shear rate varied from 0 to 100 s(-1). When further
increasing the shear rate, the pigment coatings containing NCC tended to experience a shear-thickening behavior. More importantly, NCC was
found to impart lower viscosity to pigment coatings in comparison with CMC. The presence of NCC resulted
in a marked decrease in average particle size of coatings, implying that
NCC might act as an efficient dispersion agent in pigment coatings. In
addition, it was observed that the incorporation of NCC in pigment coatings offered a relatively uniform coating layer and was effective in enhancing the hydrophobicility of coated paper.