Wet strength
The wet strength of
With combined board such as corrugated fiberboard or with laminations, wet strength also includes the ability to stay intact under humid or wet conditions. Wet strength adhesives are often needed.
Mechanism
The
Various techniques, such as refining of the pulp and wet pressing on the paper machine can be used to reduce the strength loss of the paper upon wetting. To improve the wet strength it is common to use chemicals. The use of chemicals can retain as much as 10% to 30% of the original dry strength of the paper.[1] The wet strength chemicals may improve the dry strength of the paper as well.
A Japanese research team found that the effect of humidity on cardboard differs depending on how it is dispersed. Ultrasonic mist reduces the wet strength of cardboard more so than nano-mist.[2]
Wet strength chemicals
Wet strength chemicals improve the tensile properties of the paper both in wet and dry state by crosslinking the
Wet strength development should not be confused with sizing, the first representing the strength of the paper once wet, the latter being the speed and amount of water absorbed by the paper. Normal wet strength resins are: urea-formaldehyde (UF), melamine-formaldehyde (MF) and polyamide-epichlorohydrin (PAE).
Neutral sizing agents are
Coatings
Sometimes wet strength can be obtained by curtain coating a polymer onto a paper or paperboard. Laminating a plastic film is also a method of providing wet strength.
Applications
A wide range of paper materials are wet strengthened:
Environmental considerations
References
- ^ ISBN 952-5216-04-7.
- .