Polymer solution casting is a technique that can replace film extrusion to deliver high-quality films with superior optical, mechanical and physical film properties.

In polymer solution casting, polymer is dissolved or dispersed in solution, coated onto a carrier substrate, and then the water or solvent is removed by drying to create a solid layer on the carrier. The resulting cast layer can be stripped from the carrier substrate to produce a standalone film. Before or after stripping, the cast film can be laminated with other webs or coated with other materials to create multi-layer products.

Manufacturing process advantages of polymer solution casting over traditional film extrusion methods include:

• Processing at low temperatures, which is valuable for thermally activated films or applications incorporating temperature-sensitive active ingredients.
• Ability to produce high-temperature resistant films from non-thermoplastic but soluble raw materials.
• Simplified incorporation of additives and fillers.
• Quicker changeovers for platforms with many part numbers that are differentiated based on formula.
• Single pass manufacturing of multi-layer films (g. the ability to cast a free film, then coat an adhesive and laminate release liner on one side, and coat a top coat on the other side).
• Wider range of material choices with casting from either aqueous or solvent-based solutions.

Advantages of the resulting film include:

• Greater film thickness uniformity, as tight as +/-2%.
• Wider range of film thickness, from 150 microns down to less than 12 microns.
• Films that are gel and pinhole free.
• Excellent flatness and dimensional stability.
• Isotropic orientation (mechanical and optical) as film is not stretched during manufacture.
• Absence of typical extrusion process lubricants.

The suitability of polymer solution casting is evaluated on a case-by-case basis according to the product application, base material, intended use and numerous other considerations. Specific benefits are realized for the following applications, among others:

• Acrylic and other polymer films: deliver superior optical properties and thickness uniformity.
• Polyurethane (PU) films: improve mechanical properties such as elimination of pinholes or voids; also ensures film uniformity, high optical clarity and production of thin films, which can be easily customized with added functional layers and properties.
• Thermoset adhesive films where melt extrusion is not feasible.
• Thermal interface materials: enable the addition of more concentrated thermally conductive fillers than are feasible with the melt extrusion process.
• Electro active polymer films: deliver superior optical properties, uniformity and gel and pinhole-free materials that do not provide a path for high-voltage breakdown failure.

Carestream Contract Manufacturing engineers use their extensive knowledge and experience to distinguish cases where polymer solution casting can replace film extrusion for improved quality and reduced product development costs and time. To learn more about our polymer solution casting capabilities, contact Maria Koomen.