1. Inner Diameter Selection
Determine the Size of the Object to Be Covered:
When selecting heat shrink tubes, first determine the maximum and minimum circumference of the object to be covered. To ensure enough space to accommodate irregular shapes, it is recommended to choose a heat shrink tube with an inner diameter 20% to 30% larger than the maximum circumference.
Tight Fit After Shrinking:
For the minimum circumference, select a heat shrink tube that, after shrinking, has an inner diameter slightly smaller than the object’s size to ensure a tight fit, providing good protection.
2. Shrink Ratio
Definition and Selection of Shrink Ratio:
The shrink ratio represents the ratio of the inner diameter before and after shrinking. Common shrink ratios include 2:1, 3:1, and 4:1. Higher shrink ratios are especially suitable for wrapping objects like connectors, as they can accommodate larger initial sizes and shrink to smaller diameters, such as wires or cables.
Matching Size and Shrink Ratio:
Typically, the inner diameter of the heat shrink tube should not exceed 40% of the size of the object being protected to ensure effective coverage. For example, to insulate a wire with a 3mm outer diameter, you could choose a 5mm diameter tube with a 2:1 shrink ratio (shrinking to 2.5mm), or an 8mm diameter tube with a 3:1 shrink ratio (shrinking to approximately 2.67mm).
3. Length Selection
Consider Longitudinal Shrinkage:
Heat shrink tubes typically undergo 5-7% longitudinal shrinkage when heated. Therefore, when selecting the appropriate length, this factor should be considered to ensure the tube fully covers the target object.
4. Wall Thickness Selection
Choosing Wall Thickness Based on Application:
The wall thickness of heat shrink tubes directly affects their mechanical protection capabilities. For applications requiring stronger protection, choosing a thicker heat shrink tube is more suitable, while thinner tubes are better for scenarios requiring greater flexibility.
5. Material Selection
Characteristics of Different Materials:
Heat shrink tubes are made from various materials, each suited to different working environments.
- Polyolefin:
Can withstand high temperatures of 125-135°C, durable, highly flame-retardant, and suitable for indoor or black UV-resistant outdoor applications. - PVDF (Polyvinylidene Fluoride):
Resistant to corrosive chemicals, fuels, and flames, and suitable for harsh environments. - Silicone:
Flexible and resistant to extreme temperatures, often used for insulating medical devices. - PTFE (Polytetrafluoroethylene / Teflon):
Highly resistant to chemicals, wide operating temperature range (-55°C to 175°C), and low friction coefficient. - FEP (Fluorinated Ethylene Propylene):
Similar to PTFE but at a lower cost, suitable for large-volume applications. - Dual-Wall Heat Shrink Tubes (Adhesive-Lined):
Provide waterproof sealing, suitable for marine, automotive, or RC projects, with common shrink ratios of 3:1 or higher.
6. Operating and Shrinking Temperature
Ensure Temperature Range Compatibility:
When selecting heat shrink tubes, consider the actual working environment’s temperature range to ensure the tube can maintain its insulation and protective functions within that range. For example, a heat shrink tube with an operating temperature of -55°C to 125°C may not maintain its performance outside this range.
7. Special Requirements
Meeting Specific Application Needs:
For applications requiring waterproof sealing, choose adhesive-lined dual-wall heat shrink tubes; for medical systems, select medical-grade heat shrink tubes that comply with ISO10993 certification.
Conclusion
When choosing pre-cut heat shrink tubes, it is essential to consider factors such as inner diameter, shrink ratio, length, wall thickness, material, operating temperature, and specific requirements. By referring to product specifications and related technical information, you can find the heat shrink tube that best meets your needs, providing optimal protection for your equipment.
