Specialty Plastic Films
Cellulose acetate (CA) is the most important cellulose ester. It is a tough and easy to process thermoplastic of excellent clarity and gloss and little to no odor. It has high moisture vapor transmission, exceptionally low haze, but extremely low water permeability, and is easy to cut and tear. CA is biodegradable and generally recognized as safe. It is often used for semipermeable film applications such as food packaging and drug delivery systems.
Cellulose Acetate-Butyrate (CAB) films are known for their chemical resistance and hardness. The film has high clarity, good strength and toughness, excellent scratch, UV and long-term weather resistance. It can be manufacturered with matte or with high gloss. CAB is tougher than cellulose acetate and has a lower moisture absorption which makes it a better choice for more demanding applications.
Ethyl Cellulose (EC) is another important commercial cellulose ether derivative. This film has excellent strength at room temperature but its strength decreases rapidly with increasing temperature. Like methyl cellulose, it has excellent UV resistance, but is soluble in many solvents but not in nonpolar solvents such as aliphatic hydrocarbon oils, natural oils, and greases. This makes this film useful for certain food-packaging applications and as a barrier coating for controlled drug release of pharmaceutical products. Heat sealing is difficult unless the surface is activated.
Ethylene vinyl acetate or EVA is a copolymer of ethylene and vinyl acetate. It is an extremely elastic and tough thermoplastic of good clarity and gloss with little or no odor. It has excellent adhesion to many substrates, and has good flex crack resistance, and good adhesion and heat-sealing properties. It is used in various film applications but has been replaced by metallocene PE for most food packaging because it offers faster hot tack. Nevertheless, demand for EVA remains strong for other applications like PVC replacement, solar panel encapsulation and lamination of glass to improve impact resistance.
Ethylene-vinyl alcohol copolymer or EVOH is a flexible, crystal clear and glossy thermoplastic copolymer with excellent flex-crack resistance and very high resistance to hydrocarbons, oils and organic solvents. It also has excellent barrier properties to gases such as oxygen, nitrogen, and carbon dioxide making it especially suited for preserving perishable goods like food, medical, pharmaceutical, and agricultural products.
Methyl Cellulose (MC) is the most important commercial cellulose ether. It is the simplest ether derivative where methoxy groups have replaced the hydroxyl groups. Important properties of this film are its water solubility and its gelation when exposed to heat. Although soluble in water, films made from methyl cellulose usually retain their strength and do not become tacky when exposed to humidity. MC films have excellent strength and low elongation at room temperature, but their strength decreases rapidly with increasing temperature. MC also has excellent UV, oil, and solvent resistance.
Polychlorotrifluoroethylene (PCTFE) is a transparent thermoplastic film sold under the trademark name NEOFLON. It has excellent moisture and chemical resistance, good electrical insulation properties, and very low moisture and gas permeability. It is mainly used for general insulation purposes and printed circuit boards.
Polyethyleneglycol (PEG) often referred to as polyethylene oxide (PEO) is a water soluble film. PEG is mainly used for food powder products that can be dissolved in water without opening the package.
Plexiglas film is a pure polymethyl methacrylate (PMMA) film of high clarity. It has good mechanical properties, excellent weatherability and good abrasion resistance. PMMA is sometimes coextruded with PVDF which results in outstanding chemical resistance due to the PVDF surface. Plexiglas is often used as a UV protective film to improve exterior weahtherability of laminates such as head lights. It is also used as a light scattering film that is fully transparent, has high gloss, and is easy to print.
Polystyrene (PS) is a clear, amorphous, nonpolar crystal-clear plastic film that is easy to process. Like PMMA, it is rather brittle. It is a very good electrical insulator, has excellent optical clarity due to the lack of crystallinity, and has good chemical resistance to diluted acids, bases and polar solvents like lower alcohols. However, it is attacked by higher alcohols, esters, ketones, and chlorinated and aromatic solvents. PS is not a good barrier for moisture or gases. PS (coextruded with other films) is mainly used for specialty applications in the food packaging industry.
Poly(vinyl fluoride) (PVF) is a h high performance, thermoplastic film sold under the registered trade name TEDLAR. It has excellent chemical resistance, is very tough and durable, and has exceptional low surface tension which makes it suitable as a release film. It is often used as a durable film/coating for surfaces exposed to harsh environments.
Polyurethane film, also referred to as PU and TPU film, is a flexible film with high elongation. Some grades withstand over 600 percent elongation before breaking. The properties of PU can be tailored over a wide range for a large number of application. Most grades of TPU have excellent low temperature flexibility, good strength combined with high elongation and excellent abrasion resistance. Because of its higher price relative to PVC, PE, and PP, polyurethane film is generally considered a specialty film.