TAPPI TIP 0304-69 PDF

Understanding Wet Strength: What are MRA, WRA, and WPA?

TAPPI TIP 0304-69 – Understanding Wet Strength: What are MRA, WRA, and WPA?

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.

TAPPI TIP 0304-69 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.