UV-Light and Heat Induced Fabrication of Polymer-Modified Paper by CH-Insertion Crosslinking to Enhance Wet Strength

Wet strength resins are a key additive in papermaking for products that eventually get in contact with water. This work introduces a new strategy to enhance wet strength in paper products based on a technique called C, H-insertion crosslinking (CHic). Crosslinker molecules that are incorporated into a water-soluble polymer during radical copolymerization, can be activated either photochemically or thermally in order to covalently connect the polymer chains and form a network. It is demonstrated that application and consecutive activation of these crosslinker-containing polymers leads to a significant increase for the wet tensile index of lab made paper samples. The distribution of the applied copolymers inside the paper substrates was investigated by fluorescent confocal microscopy. Variation of influencing parameters such as the applied solvent and the polymer concentration showed that the distribution of the polymeric additives can be either homogeneous or inhomogeneous, with polymer accumulations between the paper fibers. From the made observations a model was proposed to describe and predict the resulting distribution of applied additives.