Dual-surface modification of calcium sulfate whisker with sodium hexametaphosphate/silica and use as new water-resistant reinforcing fillers in papermaking

• Calcium sulfate whisker was modified with SHP to reduce the solubility.
• CSW/SHP was further modified using silica to enhance the bondability.
• 2.5–20 wt.% CSW/SHP/SiO2 fillers were used for preparing hybrid handsheets.
• The retention of the modified fillers was higher than that of unmodified fillers.

Inorganic calcium sulfate whisker (CSW) was surface modified with sodium hexametaphosphate (SHP) as waterproof modifier to reduce the solubility, and subsequently CSW/SHP was further modified using the coating of silica to improve water tolerant and enhance the bondability between CSW and wood fibers. Through the dual-surface modification, electrical conductivity (EC) of the pure unmodified CSW decreased dramatically and reached an equilibrium value of 73.9 μs·cm − 1 in the CSW/SHP/SiO2 solution. The mechanical properties of hybrid handsheets containing 2.5–20 wt.% modified fillers were investigated, and the retention of the modified fillers was higher than that of unmodified fillers.

Figure optionsDownload as PowerPoint slide