Surface characterization of nanoparticle coated paperboard

Both surface topographical and chemical composition of nanoparticle coated paperboard was characterized to explain observed differences in surface wettability. TiO2 particles induce superhydrophobicity with water contact angle (CA) of 161° whereas SiO2 particles result in superhydrophilicity with 23° water CA. The nanoparticles were generated by the liquid flame spray (LFS) process. The process was successfully used for adjusting the paperboard wettability, and has a promise to be used as a one-step, on-line coating process. The morphological characterization of reference paperboard and nanocoated samples was performed using SEM and AFM. Both XPS and CA measurements were used to evaluate chemical composition before and after nanoparticle deposition. Results for the SiO2 sample show the greatest increase in oxidation level as well as C2 carbon related groups. On the other hand, C1 carbon is on much higher level for TiO2 than was the case for the SiO2 nanocoated sample. This may be related to the replacement, or covering, of hydroxyl groups by the aliphatic chains on the surface of TiO2 nanoparticles of the superhydrophobic sample. Our results show that the LFS process can be used to create either hydrophobic or hydrophilic paperboard depending on the type of nanoparticles used for coating.