Evaluation of Four Methods to Determine the Degree of Cure of Melamine-Based Direct Pressed Laminates on Particleboards: Two Improved UV Absorption Methods, the Kiton Test, and Near Infrared Spectroscopy

Despite its importance, the determination of the degree of cure of melamine-based laminates often relies on tests with limited accuracy and validity. Undercured surfaces may suffer insufficient resistance to scratching and heat as well as substandard surface quality. Overcured melamine surfaces tend to crack and entail the inefficient utilization of the press-the panels could have been pressed for a shorter time. Four methods to determine the degree of cure of a melamine resin coating under industrial conditions were compared: the Kiton test, the most common method in industry, Near Infrared Spectroscopy (NIR) as a modern technique that allows for inline-measurements, and two novel hydrolysis methods. Each test was conducted on the same 18 panels. Each panel differed in its resin system or its degree of cure, which was adjusted by varying the pressing duration and temperature. The four methods tested were all capable of determining the degree of cure to some extent, but their applicability, the delay between the curing of the melamine resin at the final stage of production and the availability of results, and the investment and workload differ greatly. Determining the critical overcure turned out to be the major challenge. Differentiation between slight overcure, which did not affect the cracking resistance, and severe overcure, which produced surfaces with a high tendency to cracking, was possible using the NIR-based method and the two novel hydrolysis methods but not with the widely used Kiton test.