Today, localized heating is key to the performance of industrial applications. To achieve this, manufacturers use various types of flexible heating elements. These heating elements are made of different materials and can be fully customized to meet the thermal transfer requirements of an application. Silicone rubber, polyimide, mica, and butyl are a few of the popular materials used for flexible heating elements. The heating elements come in two forms: etched foil elements and wire-wound elements. With so many variations, the selection may be difficult, but this post offers tips on the selection of flexible heating elements for your applications.
Types of Heater Elements and Their Materials
In order to select a flexible heating solution, one must understand their differences. This section describes the key differences across all variables.
Heater Elements
-
Wire-Wound Elements: These heating elements feature a resistance wire of a specific diameter and contain a single strand or multiple strands. If multiple strands are used, they are woven together and placed on a fiberglass core. The wires are evenly spaced and wound in a specific pattern on every layer of a substrate. The wire is vulcanized and placed on the silicone rubber or neoprene substrate.
Wire-wound heaters are typically found in dynamic applications. They can withstand abrasive forces and can be much larger than an etched foil heater.
-
Etched Foil: In recent years, etched foil flexible heaters have gained immense popularity. These flexible heaters have no wire; rather, they look like printed circuit boards featuring thin alloy metals. The thin alloy metals are acid etched on the substrate, with widths varying from 0.005″ to 0.10″. The foil used is very thin, allowing etched foil heaters to be extremely thin and lightweight.
Etched foil heaters are typically found in more static applications where size and weight can be a big factor, but they can also be made denser for the necessary application. These heaters have rapid heat-up and cool-down capabilities, as well as high watt densities.
Materials
- Silicone Rubber: Silicone rubber is a common material for general purpose and industrial materials. Silicone rubber heaters have many benefits:
- It can be used across wide temperature ranges from -40°C to 200°C (400°F).
- Flexible heaters made of silicone rubber can be used to handle high temperatures in outdoor environments.
- It can be easily integrated into sensors, cut-offs, and thermal switches.
- Silicone flexible heaters can be manufactured as thin as 0.020 inches.
- They can be cured to fit on 3D applications.
- When vulcanized onto surfaces, flexible silicone heaters assure excellent thermal efficiency and bonding.
- Polyimide: Flexible heaters made of polyimide usually comprise an etched foil element layer placed between two layers of polyimide film. The etched foil element is held in place using various types of adhesives, such as acrylic, FEP Teflon®, and so on. These heaters feature a special type of polyimide film developed by DuPont, known as Kapton®. Kapton® flexible heaters are popular for many reasons. Here are a couple:
- Their small profile makes them ideal for 2D applications.
- They enable rapid heating and cooling.
- These flexible heaters are water and chemical resistant.
- The Kapton® flexible heaters are ideal for environments where they may be exposed to extreme temperatures.
- Mica: In these heaters, the etched foil element is positioned between two layers of mica. These heaters make use of a sacrificial adhesive during shipping, and upon installation, these heaters are clamped in place. Afterward, they are ramped up to burn away the sacrificial adhesive, leaving just the mica and foil element behind. The following features of these flexible heating elements have made them popular in various industries:
- These flexible heaters are suited for applications requiring high watt densities.
- They can work in a wide temperature range between -150°C and 600°C.
- These heaters possess fast thermal recovery times and guarantee exceptional heat transfer.
- They can be custom designed for a quick thermal response.
- Butyl Rubber: This is not a common material for flexible heating solutions. However, it has applications in a large number of industries, such as chemical detection, appliance manufacturing, semiconductors, and so on. The following properties of these flexible heaters are what makes them popular:
- The heaters can withstand maximum temperatures of up to 121°C.
- They are waterproof, chemical and UV resistant, and known for their long shelf life.
- They can have integrated thermostats molded into them to build self-regulating and waterproof assemblies.
Knowing the differences between different types of materials and heater designs will help, but it is equally important to source them from a trusted manufacturer. Birk Manufacturing is one of the leading manufacturers of etched foil flexible heaters in the US. The company specializes in silicone rubber, mica, and Kapton® flexible heaters. They are the only manufacturer specializing in butyl rubber flexible heating solutions. For more information on these flexible heaters and other details, you can get in touch with the team by phone at 860-739-4170 or by email at sales@birkmfg.com.