Polycarbodiimides (CDI) selectively react with carboxylic acid (-COOH) groups in polymer chains. This type of crosslinking reaction results in a classic 3D polymer-crosslinker network.
Compared to polyisocyanates, polycarbodiimides are much less sensitive to the presence of water and able to achieve long pot-life times. Due to the high reactivity, curing with CDI type crosslinkers can be done under typical oven conditions used for drying of applied coatings.
In addition to standard CDI crosslinker chemistry, we offer a range of 2-stage reactivity CDI crosslinkers. A second type of reactive group is attached to the polycarbodiimide in this range. Upon curing, this crosslinker not only reacts to the -COOH groups in the polymer chains, two of the reactive groups attached to separate CDI molecules can couple to form an even denser network structure. To further build on the success of our polycarbodiimide crosslinkers, we recently introduced VOC-free new CDI versions with extreme long pot-life.
White paper Polycarbodiimides
In this white paper André Derksen discusses the potential of polycarbodiimides as crosslinker for water based-coatings, including the results for different substrates and the pH and pot life effects.