FILM FORMATION MECHANISM OF 2-COMPONENT WATERBORNE POLYURETHANE COATINGS

Two component (2K) waterborne polyurethane coatings are a new technolo gy which has been demonstrated in a number of heavy duty applications. They exhibit performance properties equivalent to 2K solvent-borne po lyurethanes, with the advantage of reduced volatile organic compounds (VOCs). Although the use of these systems has been demonstrated succes sfully, the details of their film formation mechanism have not been es tablished. The objective of this work was to propose and confirm the f ilm formation mechanism of these systems. A dynamic series of interrel ated events which occur during the process was identified using a numb er of analytical techniques to study two isocyanate/hydroxyl functiona l dispersion systems. The mechanism is presented in terms of an ''even t timeline'' that chronicles the critical events which occur prior to and after application of the coating. Film property development after application also was evaluated and these results were analyzed in term s of the proposed film formation mechanism.