Wet strength

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The wet strength of paper and paperboard is a measure of how well a fiber net holds the paper together can resist breaking forces when the paper is wet. Wet strength is routinely expressed as the ratio of wet-style to dry at rest.

With combined boards such as corrugated fiber boards or with laminates, wet strength also includes the ability to remain intact in humid or wet conditions. Wet strength adhesives are often needed.

Video Wet strength

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The cellulose fibreweb paper is mainly held together by hydrogen bonds. It depends on the physical contact between the fibers and can be broken down by moistening the fibers. The residual strength of the dampened paper can be less than 10% of its original strength.

Various techniques, such as pulp purification and wet sealing on paper machines can be used to reduce the loss of paper strength during wetting. To increase wet strength it is common to use chemicals. The use of chemicals can retain as much as 10% to 30% of the paper's original dry strength. Wet strength chemicals can increase the paper dry strength as well.

Maps Wet strength

Wet strength chemicals

Wet strength chemicals improve the tensile properties of paper in both wet and dry conditions by cutting cellulose fiber bonds with undamaged covalent bonds when wet.

Different wet strength chemicals are in use, such as wet strength resin or neutral sizing agent . Normal wet strength resins are: urea-formaldehyde (UF), melamine-formaldehyde (MF) and polyamides-epichlorohydrin (PEA). Neutral adhesive materials are alkyl ketene dimers (AKD) and alkenylsuccinic anhydride (ASA). In recent years, efforts have been devoted to developing environment-friendly wet strength resins from renewable resources.

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Coating

Sometimes wet strength can be obtained by draping the coated polymer onto paper or paperboard. Laminating plastic film is also a method of providing wet strength.

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Apps

Various wet paper materials reinforced:

• Paper wipes
• Filter paper
• Liquid packaging board
• Paper bag
• Paper chemicals

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Environmental Considerations

Reinforced wet paper recycling requires a higher intensity reworking condition in the pulping process to break down web fibers. Some wet strength paper is not considered to be recyclable.

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References

Source of the article : Wikipedia