Debubbling of liquid coating layers with high intensity airborne ultrasound
Industrial coatings applied at high speed often contain bubbles from air entrapped during operation. Such bubbles will produce permanent surface defects after drying. Chemical additives are generally used to alleviate the problem, but they are difficult to dose and, if not properly handled, can create problems which may be even worse than the air retention.
High-intensity air-borne ultrasound may be an adequate contact-less method to break the bubbles. The majority of the existing studies about the application of high-intensity ultrasound in coating processes rely on the deaeration of the coating liquid previously to the coating process. Nevertheless, many of the bubbles within the coating layers are produced during the coating application. This work deals with a new process based on the direct application of air-borne ultrasound to break the bubbles which are semi-submerged within the coating layer.