Polyamidoamine epichlorohydrin (PAAE) wet-strength agent: Generations, application, performance, and recyclability in paperboard and linerboard

Polyamidoamine epichlorohydrin (PAAE) is the preeminent permanent wet strength additive used in papermaking. Wet strength additives are used to improve paper resistance to a rupture force in wet environments. The invention of PAAE in 1957 was an innovation, as it improved paper properties by giving superior wet strength in humid or wet conditions. It was rapidly adopted by the industry. Despite PAAE’s long history, the mechanism of PAAE interaction with fiber has not been fully understood. Therefore, fundamental understanding of PAAE mechanism needs to be investigated to improve its utilization in making sustainable paper products. These areas include an understanding of repulping methods and optimal PAAE dosages for better cost and performance. This paper investigates different generations of PAAE, the application method, and its impact on paper recyclability. Three generations of PAAE are currently on the market with at least two newer iterations under development. Critical application parameters that need to be understood include determination of the bonding mechanism, optimal dosage, and retention parameters. The main drawback of PAAE application is it makes paper recycling difficult. Several repulping methods are proposed for better recyclability and sustainability in the papermaking process.