The characteristics of polyester electric insulation film
Polyester is the most common type of material used for electrical insulation film because of its physical and electrical insulation properties. Polyester films can be characterized as PET (polyethylene terephthalate) or PEN (polyethylene napthalate). The differences between the two polyester films are their chemical composition and their physical and electrical insulating properties. PET films are known for their good dielectric withstanding resistance within a relative temperature range (Tg of 78oC). PEN films provide a similar performance but at a higher temperature range (Tg of 120oC). When the application involves higher temperatures, PEN film is a better option given its greater stiffness in temperatures that are above 125oC and its 20oC greater operating temperature. However, the drawback to PEN electrical insulation film is its cost. It may be negligible though for a critical application particularly since this electrical insulation film is widely used for flexible electronics, battery and motor insulations and for electrical components.
Polyether materials as an alternative to PEN films
When the higher temperature in the environment does not allow the use of PEN films, polyether ether ketone (peek) or polyetherimide (PEI) materials can be used. PEI has a significantly higher glass transition temperature at 216oC with a continuous operating temperature rating at 171oC meaning it has an exceptional flame and heat resistance. The availability of PEI in sheets, film and extruded rod forms gives designers more flexibility because they can choose the form that is applicable to the specifics of the application. However, the issue with PEI is again its cost because it is more expensive than PEN or PET films. Some applications would do better with PEI like aircraft components, microwave applications and electrical components.
Polyimide materials when greater temperature resistance is required
Polyimide electrical insulation film is an outstanding insulating material that is often utilized as an alternative to PEI in critical applications for precision engineered materials. The glass transition temperature of a polyimide film at 351oC exceeds that of PEI and it provides exceptional stability even at demanding temperatures. Polymide films also have a very low coefficient of thermal expansion at 200ppm/oC along with a high tensile strength of 32,000 psi @ 200oC at 9ml. These characteristics of polyimide film make an exceptionally strong and stable material and it provides design engineers with greater flexibility because they do not have to worry about material thickness limitations knowing that there is always an available material to address their needs for thickness. On the other hand, it is important to consider machining time to achieve the final thickness tolerances for manufacturability.