PTFE/ FEP dual wall heat shrink differentiates itself in that it merges two different fluoroplastics: PTFE and FEP. Consisting of an outer sleeve of PTFE heat shrink with an integral inner wall of FEP, the heat shrink encapsulates and protects components. So, why use dual wall heat shrink?
PTFE/ FEP dual wall heat shrink pots components in pure fluoroplastic. When the PTFE outer sleeve is shrunk down, the FEP inner sleeve melts and flows over the component. When cooled, the fluoropolymer heat shrink completely encapsulates and seals the component. This offers a superior protection against moisture, mechanical exposure and chemicals, even in immersed conditions.
Dual wall heat shrink is the fluoroplastic alternative to Polyolefin adhesive-lined heat shrink. Thanks to its PTFE outer sleeve, the heat shrink offers many benefits: non-stick and lubricious properties, as well as resistance to high temperatures, chemicals and electricity. In addition, PTFE heat shrink is ideal for covering complex profiles, shapes and terminals.
Due to its FEP inner sleeve, PTFE/ FEP dual wall heat shrink can only withstand an upper continuous working temperature of +200°C. For higher temperature applications, PTFE heat shrink sleeving with an inner wall of PFA is recommended.
If covering a large thermal mass, the component needs to be preheated in an oven at 400°C to prevent the chilling of the PTFE heat shrink which would cause a loose fit. PTFE shrinks at 330°C with a hot air gun or oven temperature of 440°C, so the component to be encapsulated needs to withstand this temperature.
The PTFE outer sleeve needs to be fully and evenly heated and shrunk to the specified recovered ID. This will ensure the temperature is high enough to melt and flow the FEP inner sleeve and completely seal the component. However, overheating and unevenly heating the material could lead to brittleness and cracking.
You can find detailed heat shrink instructions in the How to shrink fluoropolymer heat shrink article.
The unique properties of the fluoroplastic dual wall heat shrink sleeving lends its use in any application that requires a high working temperature, non-stick surface, high electrical resistance and chemical resistance. As such, applications include wires, cable harnesses, connectors and terminals.
PTFE/ FEP dual wall heat shrink is ideal for encapsulating components, sealing electrical connections and cable terminals, and splicing wires to protect them against moisture, corrosive fluids, chemicals and mechanical exposure.
The fluoropolymer dual wall heat shrink is also perfect for covering temperature sensors and their fittings and connectors. The temperature sensor is encapsulated in FEP, while the termination fitting is covered in PTFE. This seals the whole component against any chemicals and stops any ingress.