Understanding wet strength: what are MRA, WRA, and WPA?, Technical Information Paper TIP 0304-69 (2017)
To determine the “wet strength” needs of a corrugated box plant, one must first define the level of “wet strength” needed. Generally, the industry has accepted three levels of “wet strength” adhesive.
1. MRA – moisture resistance, used for the lightest possible applications.
2. WRA – medium level of water resistant performance.
3. WPA – highest level of water protection performance.
This Technical Information Paper will identify the key characteristics of each type of “wet strength” adhesive and when it would be used. Proper test methods to determine the level of water resistance of a particular box will be discussed.
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Understanding wet strength: what are MRA, WRA, and WPA?, Technical Information Paper TIP 0304-69