Characteristics and Usage of Polyester and Polypropylene Film

by Rohan Sinha Author

What is Film Capacitor?

Film Capacitor is a non polarized capacitor which is popular due to its low cost and versatility. Film Capacitor is made using thin plastic films. These plastic films are metalized and sometimes it is called as a metalized capacitor or plastic capacitors.

There are Film Capacitors primarily based on the type of plastic dielectric material used in the capacitor, out of which the most commonly used are Polyester Capacitor and Polypropylene Capacitors. The polyester capacitor is also called as polyester film capacitor which is made of a polymer called Polyethylene Terephthalate (PET). The polypropylene capacitor is another type of film capacitor known as polypropylene capacitor or PP Film Capacitor.

Polyester Capacitor is one of the film capacitor which is widely used dielectric materials. It has a high dielectric constant compared to polypropylene. The high dielectric permits creation of capacitors with small bodily sizes. Polyester capacitors, additionally referred to as mylar capacitors, have top self-recovery properties and are highly cheap.

At excessive temperatures, polyester capacitors use up extra power. This characteristic makes these capacitors unsuitable for prime frequency associated high current AC applications. Polyester exhibits a major capacitance change up to 5% as temperature approaches low or high-temperature limits. Because of this characteristic polyester is unsuitable material. They are mostly used in blocking, bypassing, decoupling and a few noise suppression circuits.

Characteristics of Polyester Capacitor

· Leaded versions: Polyester capacitors are not available in surface mount packages. They are only available in leaded versions.

· High dielectric strength: It offers a high dielectric strength which is referred to as PET. Because of high dielectric strength, high voltage capacitors can be made relatively small.

· Tolerance: The tolerance capacity of polyester capacitors is 5% to 10%, which is sufficient for many applications; however they are available at lower cost these days.

· ESR: Polyester provides a low level of equivalent series resistance.

· High dv/dt: The production and dielectric of polyester, PET capacitors can be used in applications where fast rise time spikes are present, as they will be able to accommodate high dV/dt figures.

Polyester capacitors are used in various applications. Here are some polyester capacitor applications:

· Circuits in which the capacitor must handle high peak current levels.

· Filters that do not require high tolerance levels.

· General coupling and decoupling packages and DC blocking

· Power substances where the very high capacitance levels of electrolytic capacitors are not needed.

· Audio applications.

On the other hand, polypropylene is commonly used in the development of capacitors for prime frequency AC applications. This dielectric material encompasses a low dissipation factor, high breakdown strength, low dielectric absorption, high insulation resistance and is instantly available. These properties build polypropylene a dielectric material of selection for a variety of applications including snubber circuits, high frequency AC systems, high voltage DC and AC systems. This capacitor can be operated over a wide temperature range. As compared to polyester, the capacitance of polypropylene capacitor decreases with temperature. Polypropylene is more expensive compared to polyester.

Polypropylene is widely used films and it is used in many applications including protecting stationary and archival products like baseball, packaging of candies, foods etc. Here are few applications or industry area of Polypropylene Film.

· Clothing: It is used for the fabrication of clothes like underwear, long-sleeve shirts.

· Medical: Polypropylene is often used for sanitary products, diapers.

· Food & Beverage: Used in packaging food and beverages. It is an ideal choice for barrier film to block moisture, oxygen and light.