Blister Resistance of Coated Papers Versus Latex and Polymer Properties, 1991 Coating Conference Proceedings

Blister resistance of coated papers for web-offset printing will require continued improvement, especially with the higher speeds and more powerful drying of the "four color" offset presses. Coating weight increases and decreased use of high quality fibers are two other factors which increase the need for improved resistance.

The literature clearly shows that the porosity and structure of the coating layers do not fully explain the blistering behavior. Latex properties, such as vapor permeability and polymer rheology under blistering conditions of pressure and temperature, could be of prime importance.

We have studied the influence of several latex and polymer features to answer these questions. Original methods, such as the high temperature capillary rheology of SB polymers, the dynamic mechanical analysis of polymers and the vapor permeability determination were developed for these investigations.

Behavior of the polymer at high temperature is clearly the key to the phenomenon. Major characteristics such as pseudoplasticity and viscosity of the melted polymer are dependent on the crosslinking structure of the polymer and help us to understand the compromise between blister resistance and coating cohesion. Moreover, it is shown that water vapor permeability of the polymer is not involved in the blister phenomenon.