How to select heat shrink tubing?

Heat shrink tube is versatile, easy to use, and finds wide applicability in maintenance and repair. Every electrician knows its benefits. Although it is a simple and effective way of improving a cable’s appearance, selecting a proper heat shrink tube could be a problem in some applications.

Before describing the selection parameters, I want to define the heat shrink tubing.

The heat shrink tubing is a plastic tube that shrinks permanently when heat is applied.

Heat-shrink tubing is available in an array of materials and options. But, a few of the general-purpose materials will usually cover most needs. The majority of heat shrink is made from cross-linked materials that do not melt and flow. They soften and become rubbery but still hold their basic shape. The main benefit is improved thermal, physical, and chemical resistance. The most popular material is a polyolefin, which can be used unless your requirements have special considerations. To select a proper heat-shrink tubing you have to consider the below parameters. It can be used for making minor repairs and maintenance to cables and connectors. It is the optimal solution for insulating components against heat and electric current.

It provides strain relief for connectors and splices and protects against water ingress, chemicals, and abrasions. Versatile in solving design challenges efficiently, heat shrink tubing has also been shown to outperform tape, glue, and glass alternatives, particularly when it comes to impact resistance and operating in harsh environments.

How to select heat shrink tubing?

Heat-shrink tubing is available in an array of materials and options. But, a few of the general-purpose materials will usually cover most needs. The majority of heat shrink is made from cross-linked materials that do not melt and flow. They soften and become rubbery but still hold their basic shape. The main benefit is improved thermal, physical, and chemical resistance. The most popular material is a polyolefin, which can be used unless your requirements have special considerations.

To select a proper heat-shrink tubing you have to consider the below parameters:

Shrink ratio

Shrink ratio is an expression of how much the inside diameter of shrink tubing will reduce in size when recovered. Generally, don’t use a higher ratio than your application requires.

For example:

2:1 shrink ratio: 1/2″ will recover to 1/4″ — 50% shrinkage.

3:1 shrink ratio: 3/4″ will recover to 1/4″ — 67% shrinkage.

Sleeve diameter

The final shrink diameter should be smaller than the object that the sleeve is applied to. Put another way, you don’t want to shrink the sleeve completely. The sleeve should shrink tightly against the object, which won’t happen if the object is smaller than the final shrink diameter.

Longitudinal shrinkage

Longitudinal shrinkage is the change in length of tubing when recovered. Expressed in the percent of change from the original length.

Heat shrinkable tubing has a small loss of length during the recovery process. Take into account the change of length of the recovered tubing (after shrinking). Longitudinal shrinkage varies from 5% to approximately 15% – depending on the material.

Wall thickness

Wall thickness is the thickness of the applied insulation or jacket. Heat-shrink sleeves come in various thicknesses. A thicker wall provides more abrasion resistance, rigidity, and the ability to withstand wear and tear. If you don’t need such robustness, a thin-wall sleeve is fine.

Stiffness

Different sleeves have different degrees of flexibility. A more rigid sleeve is a good choice for achieving strain relief on a connector or terminal, where reducing flexing is one goal of the heat-shrink tubing.

Sealing

Heat-shrink tubing, properly applied, will seal the interface between the tubing and the object. If sealing is important, choose a material that will withstand any unique contaminants. For the best shielding, try to limit the shrinking to 75% to 80% of the maximum. For a 0.500 sleeve with a 2:1 shrink ratio, the object should not be less than 0.32 inches to ensure proper sealing. Some heat-shrink tubing features an adhesive or meltable inner layer for applications that require maximum sealing. In most cases, standard tubing will provide adequate sealing, but adhesive-lined tubing goes a step further.

Shrink temperature

Shrink temperature is the minimum temperature at which a product begins to recover. A tube with a lower shrink temperature will generally shrink faster. Products with higher shrink temperatures generally have higher performance. Common polyolefin materials have a recommended shrink temperature of around 90°C, although other materials offer shrink temperatures, notably Teflon, as high as 250°C.

The usual considerations

You must consider the basic application requirements of voltage, operating temperature range, and other typical concerns in any application. You also need to consider special application needs, such as resistance to chemicals and oils.

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