Saturation coating, which is also known as impregnation coating, is used to coat porous substrates. Substrate structures may consist of pores that penetrate through the entire substrate. By using a saturation coating process, the entire internal web structure is coated, which will fill the pores with thermoset polymeric resins that work to reinforce the entire substrate. These filled pores can either have a surface coating or a non-surface coating. The result form adding a saturation coating is a solid, modified substrate, with a surface now consisting of different characteristics as opposed to when the substrate was uncoated. In addition, the saturated coating enhances the strength of the substrate, while still maintaining flexibility. In essence, the impregnated, or saturation coated substrate now can be considered a utility substrate due to the modifications made, because it can be used for more functional capacities. Substrates made of fiberglass, Kevlar, Woven Carbon Fiber, paper and spun bonded webs are the most typical that receive saturation coating, because these substrates are found in a large variety of products. Some of these products include circuit boards in electronics, tapes used for reinforcement, advanced composites for use in latest generation fuel efficient aircraft, and finished decorative components that can be found in automobiles.
The saturation coating process requires two steps. In the first step, the substrate is completely immersed in a dip tank that contains a polymeric resin that dissolves in a solvent, which will completely fill all of the pores. The dip tank can use both single and multiple rolls that work to control the resident tank. The application of specific pressure, permeability of the type of substrate, solution viscosity, and the dwell time in the coating dip tank all work together to determine how effectively the saturation coating flows into the pores, covers the pores, and how much of the pores will be covered. When proceeding to the second step, the final coating weight is determined by removing all of the excess coating solution by implementing any of the several doctoring coating methods designed specifically for removal of excess solution. Some of these methods include a pair of metering rolls where the gap between the substrate and the rolls determine the coverage, or a web scraper that can be used to remove excess solution in the dip tank.
The saturation coating, or impregnation machine, has the same basic components as several other types of coating methods, such as a standard surface coater and a substrate unwinder. Keep in mind that the tension control used for saturation coating needs to be more precise because of its lighter web, which can become easily distorted by too high of a tension level.
Jessup Manufacturing offers saturation coating (impregnation) solutions. For more information on this solution, and to find out if this coating application is right for your products, contact Jessup, and a representative will happily analyze your coating needs.