Proper Selection and Standardized Operation of Heat Shrink Tubing for PVC Insulation Busbar

The first step in correctly using heat shrink tubing is proper selection. The appropriate size should be chosen based on the outer diameter of the object being covered. The nominal size of heat shrink tubing typically refers to its inner diameter before shrinking; however, in practical applications, it is essential to ensure that the tubing fits snugly after shrinking. For instance, heat shrink tubing with a 2:1 shrink ratio can cover objects with a diameter up to twice its post-shrink inner diameter. For cable joints, it is recommended to select a product whose post-shrink inner diameter is slightly smaller than the cable's outer diameter to ensure an effective seal. In electric vehicle (EV) battery systems, highly flexible heat shrink tubing is often applied around EV battery connectors to accommodate vibration-prone environments and prevent corrosion by electrolytes.

Prior to application, the surface to be covered must undergo pretreatment. It is crucial to remove any burrs, sharp edges, or oil residues; otherwise, during the heating and shrinking process, sharp points could puncture the tubing wall, leading to insulation failure. It is recommended to clean the surface using a quick-drying electronic cleaning agent to ensure it is free of dust and grease. This step is particularly critical for heat shrink tubing applied to busbars, as processing burrs on the busbar edges can easily trigger localized dielectric breakdown during the heat-shrinking process.

When cutting heat shrink tubing, the cut edges should be flat and smooth to avoid creating tears or frayed edges. Irregular cuts can create stress concentration points during heating, potentially leading to cracking during shrinkage. The cut length should be slightly longer than the area requiring coverage, allowing for an overlap margin at both ends to enhance sealing integrity. For complex structures-such as bent wire harnesses-the heat shrink tubing should be slipped into place beforehand and properly positioned prior to heating to prevent wrinkling or voids from forming around the PVC-insulated busbar after shrinkage.

Heating is the critical stage in the heat shrink tubing application process. It is recommended to use a heat gun, an oven, or specialized heating equipment; direct exposure to open flames should be avoided. During heating, maintain a distance of 4–5 centimeters between the nozzle and the tubing surface, moving the heat source uniformly at a 45-degree angle-either from one end to the other or from the center outward-to ensure even heat distribution. Localized overheating can cause the PVC insulation on the busbar to soften excessively or even carbonize, while insufficient heating results in incomplete shrinkage, compromising both sealing and insulation performance.

Particular attention must be paid to ensuring that the heating temperature remains strictly within the material's specified thermal tolerance range. For most polyolefin heat-shrink tubing, the onset of shrinkage typically begins at 70°C, with full shrinkage achieved at approximately 125°C. Exceeding this upper temperature limit (e.g., above 150°C) will cause the material to melt and flow, resulting in a complete loss of its shrinkage capability. Therefore, operators must be thoroughly familiar with the thermal performance parameters of the specific heat-shrink tubing being used to prevent damage caused by excessive tool power or prolonged exposure times.

To suit diverse application scenarios, the type of heat-shrink tubing selected must be precisely matched to the specific requirements. General-purpose polyolefin tubing is suitable for standard wire harnesses; however, waterproof heat-shrink tubing is recommended for use in humid or outdoor environments. Conversely, busbars located within electrical cabinets require specialized Busbar Insulation Sleeves, which feature superior dielectric strength and higher flame-retardant ratings. In the new energy sector, heat-shrink tubing with a dual-wall adhesive lining is frequently paired with battery terminal busbars; during the shrinking process, the inner layer of hot-melt adhesive fills any voids or gaps, thereby achieving an IP67-rated seal.