Block Resistance of Low-VOC Acrylic Paints: Influences of Latex Design Parameters

By Wenjun Wu, Michael Anderson, Jeff Schneider

One of the biggest challenges for low-VOC coatings is simultaneously attaining smooth film formation and acceptable block resistance and film hardness. Block resistance is a function of bulk and surface properties. This article investigates the influences of some latex design parameters on block resistance of acrylic paints. The effects of latex particle size, surfactant choice, and polymer Tg are discussed.

Dry paint often comes in contact with itself, such as during the closing of windows and doors. Block resistance combats the tendency of paint films to stick together (or block). It is a key performance requirement for gloss and semi-gloss paints. A coating with good block resistance will retain its film integrity upon reopening of a window or door.

Poor antiblocking properties cause the two contacting films to stick, resulting in tearing or peeling of the paints upon separation. The blocking behavior of a paint film depends on its hardness, the pressure, temperature, humidity, and the duration of surface contact.