How Can I Prevent Curtain Break and Egging in My Adhesives?
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The thin, falling film of an adhesive applied by curtain coating can be disrupted by air currents, bubbles, grit or poorly dispersed solids. These disturbances, either in the main film or at the edges, create waves that can propagate at speeds that will break the curtain if they exceed the curtain speed. One way to reduce this wave propagation and avoid curtain break is to lower the surface tension of the adhesive with surfactants. The surfactants, however, must be very fast acting because both surfaces of the falling curtain exist only for milliseconds between creation and substrate contact.
Surfactants such as Surfynol® 440 and 2502 and superwetters like Dynol™ 800 and 810 are highly dynamic wetting agents that can quickly lower the surface tension of the falling curtain after creation. These anti-foaming surfactants are also highly effective at wetting substrates like release liners and tapes.