Cellulosic thickeners have high thickening efficiency, especially for the water phase. Less restrictions on paint formulation and wide application; large pH range. However, there are disadvantages such as poor smoothness, more splashing, poor stability, and easy microbial degradation.
Because it has low viscosity under high shear and high viscosity in static and low shear. The viscosity increases rapidly after the coating, which can prevent flow hanging, but on the other hand, it causes poor smoothness. It has shown that the relative molecular mass of the thickener increases, and the spatter of latex coatings also increases. Cellulose thickener are prone to splash because of their relatively large molecular mass.
The thickening mechanism
The thickening mechanism of cellulose thickening agent is that the hydrophobic backbone associwith the surrounding water molecules through hydrogen bonding. Which improves the fluid volume of the polymer itself, reduces the space for free activity of particles. And thus improves the system viscosity. The improved viscosity can also be achieve by the winding of molecular chains. Which is manifeste as having high viscosity at static and low shear, and having low viscosity at high shear. This is because the system is disordered when the cellulose molecular chain shows high viscosity; at static or low shear spee, the molecules are arranged parallel to the flow direction and easy to slide with each other, so the system viscosity decreases.