Wet Strength Agent

Definition

1. Papermaking auxiliary that enables paper to retain ≥15% of its dry strength when soaked, resisting breakage in water.

   
   

2. Working Principle

• Self-crosslinks under heat to form a waterproof film blocking moisture.

• Forms water-resistant covalent bonds with cellulose to lock fibers together.

3. Comparison of Main Types

• PAE (Mainstream)

  Formaldehyde-free, suitable for neutral papermaking, excellent wet strength, non-brittle paper, easy waste paper repulping; for napkins, paper cups, food packaging, medium-high cost.

  
  

• MF Melamine-Formaldehyde

  High wet strength, contains formaldehyde, prone to yellowing and brittleness, hard waste repulping; used for drawing paper, banknote paper.

  
  

• UF Urea-Formaldehyde

  Lowest cost, high formaldehyde content, poor wet strength, brittle paper; applied to low-grade paperboard.

  
  

4. Application Guidelines

   Add to stock before fan pump / headbox and mix thoroughly with pulp.
   Cure fully at dryer temperature ≥105℃.
   Normal dosage: 0.8%~3% based on oven-dried pulp.

   
   

5. Applicable Paper Grades

   Napkins, kitchen towels, paper cups, tea bag paper, map paper, filter paper, medical paper.