The influence of starch-based bio-latex on paper coating
The microstructure of coating layers has important effects on final properties of paper. Eco-friendly bio-latex derived from sustainable starch has being increasingly used in paper coatings to substitute part of the petroleum-based synthetic latex as pigment binder.
The influence of starch-based bio-latex on microstructure and surface properties of coatings such as surface composition, surface morphology, void fraction and water absorbency was studied in this paper.
X-ray photoelectron spectroscopy (XPS) results showed that bio-latex addition led to a nearly linear decrease in surface carbon content for coatings dried at high temperature. Scanning electron microscope (SEM) images demonstrated that bio-latex addition may cause a lack of binder film at the coating surface that binds pigment particles, which was in agreement with the XPS results.The coatings demonstrated a marginal increase in surface roughness and some decrease in gloss with the addition of bio-latex, as was expected when starch-based binder was used.
Bio-latex addition may lead to unexpected increase in coating porosity
Unexpectedly, the void fraction of coatings increased slightly, which was contrary to the case in conventional cooked starch. The coatings had a significant decline in water contact angle after bio-latex addition, indicating a considerable increase in water absorbency. The changes in coating microstructure may be attributed to the unique core-shell structure and water-swollen nature of starch-based bio-latex particles.
The study is published in: Progress in Organic Coatings Volume 116, March 2018, Pages 51-56.
