The purpose of this TIP is to explain and standardize some of the terms.

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.

Mills can utilize a number of techniques to achieve higher compression strength, including improved fiber orientation and cross-linking, and high-density formation of mixed paper fibers through high loading rates of their presses. This resulting densification process compresses the fiber matrix tighter, typically increasing the sheet's density and strength.

These newer engineered sheets as defined above are often less porous than the typical Kraft liners utilized in the past. These tighter sheets with increased fibre-to-fibre bonding Decreased porosity levels can translate into reduced adhesion penetration, potential bonding problems, and box performance failures. Typical adhesives formulated to bond conventional Kraft liners may appear to bond well initially but can delaminate soon after curing due to the liners ability to hold heat longer.

These contemporary containerboards are thought to bind up their moisture differently than standard or more open liners. (This is too much paper physics to explain here). These liners require reduced heat transfer levels and improved preheater wrap techniques to prevent premature adhesive gelatinization and brittle bond formation. This Technical Information Paper offers techniques to successfully combine a range of densified, containerboards produced with OCC/DLK and mixed office waste now available to the corrugated industry.