Visualization of Wire Wound Rod Coating Defects, 1990 Polymers, Laminations & Coatings Conference Proceedings

Wire wound rod applicators have been used in the adhesives and coatings industries for many years. Such coaters boast low cost equipment and excellent coat weight versatility as major advantages. A disadvantage has been the quality of the coating due to defect lines in the coating running in the machine direction. These defect lines are often referred to as “rod streaks” and the assumption is made that the defects are caused by the wire wrap on the rod or the contact of particulate matter in the coating with the rod. It can be shown however, that these defects are more closely related to the “ribbing” type of defect seen in roll coating. The major tool in examining these defects is a set of photographs taken of a rod coater in a dynamic coating situation. Through manipulation of various machine conditions, the number and frequency of the defects can be altered. An examination of the relationships derived from roll coating research can then yield some indications of actions to be taken to reduce the severity of rod coating defects.