Heat Shrink Tubing Solutions

coaxial core

PTFE/FEP Dual Wall Heat Shrink Tubing

Markel : Heat Shrink Tubing : Dual Wall Heat Shrink Tubing

Markel PTFE/FEP Dual Wall Heat Shrink Tubing consists of an outer layer of expanded PTFE over an inner layer of FEP. When heated, the outer PTFE layer supplies the compressive force, while the inner FEP layer melts and fills in any voids or open space around the fitting being covered.


Dual Wall Heat Shrink Tubing is required where it is necessary to ensure no liquid or gas comes in contact with the fitting being protected. Sensitive components, parts subject to oxidation or corrosion, or other applications requiring the component be completely encapsulated are ideal candidates for Dual Wall PTFE/FEP heat shrink tubing.

Choosing the Right Dual Wall Heat Shrink Tubing for Your Application

It is important to select the optimal size and shrink ratio for your particular application. The inner diameter of the expanded heat shrink tube should conform as closely as possible to the OD of the part being covered while still allowing an easy insertion of the part into the heat shrink tube or sleeve. Like FEP Heat Shrink Tubing and PTFE Heat Shrink Tubing, careful temperature control and exposure time are critical for successful application of the dual wall tubing. Too much heat or for too long a time will cause the PTFE/FEP dual wall liner to soften too much and drain out of the tubing. Too little heat or too short a time and one will not realize full encapsulation. The orientation of the part in the oven is also important for optimal coverage.


Markel PTFE/FEP dual wall heat shrink tubing is offered in a variety of diameters as shown on the accompanying tables. If you have questions about your particular application, do not hesitate to contact a Markel engineer.

Dual Wall Heat Shrink Tubing

Heat shrinkable FEP tubing is activated at a temperature of 650°F (343°C). As with the PTFE Heat Shrink Tubing, exact conditions are best determined on an application specific basis. Both the nature of the part being covered and the design of the oven or heat source will alter the required time and temperature to recover. It is important that for optimal results, the heat is applied evenly to all sides and that the part is unconstrained so that it is free to move longitudinally. Larger or heavier parts will require longer times as they will act as heat sinks.


Whenever working with any heat shrinkable product, ensure that there is good ventilation around the work area. Fumes from any fluoropolymer heat shrinkable tubing should be avoided as they may result in dizziness, nausea, or headaches.


Ovens (as opposed to heat guns) are the best way to apply heat shrink tubing uniformly as they offer the most uniform temperature profiles. Care should be exercised to ensure that in the case of convection ovens, the air velocity does not dislodge the heat shrink tubing from the part to be covered.

Dual Wall Heat Shrink Tubing Recovery Procedures

1. The Markel PTFE/FEP Dual Wall Heat Shrink Tubing should be trimmed to length and tested for fit prior to exposure to heat. The tubing should slide easily into place, but have enough of an interference fit to remain in place during the heating process.


2. Ensure the part to be covered and the inside surface of the heat shrink tube are free of dirt, dust, or particles.


3. Markel PTFE/FEP Dual wall Heat Shrink Tubing should be heated to 650°F (343°C). The duration of the heating process will vary depending on oven conditions and the geometry of the part, but excessive heating should be avoided.


4. The part being covered by the heat shrink will act as a heat sink and may impact how the tubing shrinks. If you notice wrinkles, uneven shrinkage, or other signs of uneven application, consider preheating the part to an elevated temperature, but remaining below the heat shrink temperature referenced above.


5. The final dimensions of the PTFE/FEP Heat Shrink Tubing will depend on exact clearances with the part covered. If there is little room for radial recovery, the tubing will tend to contract longitudinally. Too tight a clearance may also result in splitting the wall of the Heat shrink Tubing.