Impact of recycled fiber content on tissue paper wettability

• Recycled fibers addition shows a quadratic relationship with tissue wettability. • ATR-FTIR reveals hydroxyl group loss due to hornification. • 34.3% recycled fiber content optimizes surface energy. The use of recycled fibers in papermaking is critical for sustainability, cost reduction, and energy efficiency. However, their incorporation into tissue paper may adversely affect product properties. This study investigates the impact of recycled fibers on tissue paper wettability by analyzing a mix of wood and recycled fibers. Results indicate that as the recycled fiber ratio increased from 0 % to 100 %, surface hydrophilic functional groups increased at first and then decreased, and surface free energy also increased from 152 mJ/m 2 to 191mJ/m 2 and then decreased to 115 mJ/m 2 . The highest surface free energy appeared at the point of 34.3 % of recycled fibers. These findings demonstrate that a better control of recycled fibers content could improve tissue paper wettability, also providing a potential method for detecting recycled fiber content in paper products.