For PTFE heat shrink tubing we provide standard shrink ratios of 2:1 and 4:1. Larger ratios are technically possible, but not standard and custom made. The shrink ratio for FEP heat shrink tubing is lower, on average 1.3:1 up to 1.6:1. The stated dimensions are minimum dimensions; in practice the diameter may be 10% larger. This applies mainly to the small dimensions.
A tight connection between object and shrink tubing can be obtained by using the so-called PTFE/FEP heat shrink tubing. The PTFE/FEP heat shrink tubing consists of an inner layer of FEP heat shrink tubing and an outer layer of PTFE heat shrink tubing. The process temperature of PTFE heat shrink tubing is approximately 340°C and can also be observed visually. When the temperature is reached, the material becomes clear transparent. The shrink temperature of FEP is in between 160°C and 220°C. An overheating can lead to rupture and the tube will also loose its shrink ability.
When using PTFE heat shrink tubing there is a risk that the object, which needs to be covered, absorbs the excess heat. In this case the tube does not shrink tight around the object. This can be prevented by heating both parts to shrink temperature. The heating has to be equal on all sides. Uneven heating and cooling often leads to wrinkles and tears. As a heat source you can use a furnace, infra-red beamer, hot-air gun or even a bright flame.
In addition to shrink in radial direction, shrink in axial direction can occur as well. Length reduction can be approximately 15-20%.
Please contact our sales engineers if you require more information, an inquiry or to evaluate samples. Or download our technical data sheets.