MECHANISM STUDY OF PAPER STIFFNESS IMPROVEMENT BY SURFACE SIZING APPLICATION OF WATERBORNE EPOXY RESIN

Low basis weight paper lacks normal strength and stiffness. Waterborne epoxy resin can be employed to improve paper stiffness through surface sizing, coordinated with oxidized starch. In this paper, the mechanism of enhancing stiffness by adding waterborne epoxy resin was investigated. The results indicated that through surfacing sizing with epoxy resin, paper thickness remained unchanged, while the elastic modulus increased significantly. The epoxy resin also had a positive impact on single fiber strength. A rigid resin layer and interpenetrating polymer network formed on the surface and in the inner layer of the paper, respectively. The formed resin layer and interpenetrating polymer network strongly supported the paper, leading to the improvement of elastic modulus and stiffness. The stiffness enhancement through surface sizing is mainly due to a composite layer formed among the fibers and along with penetration of the sizing agent into the paper. The better the interaction between fiber and sizing agent and the higher the elastic modulus, the more stiffness is contributed by the composite layer to the paper as a whole.