Critical Pigment Volume Concentration Measurements – A Very Fast Method

By Walter K. Asbeck

Because of the importance of knowing the Critical Pigment Volume Concentration (CPVC) for maximum performance of all pig­mented coating systems, a large number of methods to measure CPVC have been proposed. All at­tempts to predict the critical point on theoretical grounds have been unsuccessful. Some tests for CPVC are quite accurate and reliable in showing where the break in the for­mulating ladder exists. Some re­quire considerable judgment.

All tests for CPVC, unfortunately, require the preparation of the coat­ing compositions, including pig­ments used, vehicles (both solution and latex type), and their grinds. The composition must then be de­posited on some substrate and dried either by air or bake-before the classical tests can be used. All facets of the coatings manufacture must be included in the test sam­ples. The required sample may be produced relatively fast in the case of baked systems or very slow in the case of some air-dried systems.

All of the classical tests made on these PVC ladders are relatively time consuming and total testing time may require many hours. A new method of testing on the PVC lad­der, which is both very fast and re­quires minimal instrumentation, is proposed here. For the most part, the tests on each sample can be made in less than one minute.