Coating is the physical process of laying a liquid or solid onto the surface of a paper, fibre or fabric. The objective is to achieve uniformity of coverage (uniformity of weight distribution) while controlling the variance of thickness of the coating. Coating is most typically seen in pre-preg systems for the application of a resin to a paper or film.
Impregnation is the transfer of the additive agent (coating liquid or solid, finishes, washing agent) into the bulk of the fibre or fabric substrate. With impregnation the depth transfer of the additive is a process objective and a control parameter. Impregnation can be achieved via mechanical treatment of the substrate while a coating agent is applied. Impregnation is also frequently achieved through full emersion of the substrate into a bath of the additive agent, such as in spin finish and sizing application.
Coaters can be supplied as part of an integrated process, and coaters can be supplied as stand-alone components for unique machine configurations.
Common features include:
The coating and impregnation system formats include: