Heat shrink tubing, widely used for electrical insulation and wire protection, varies in flammability depending on its composition and flame-retardant properties, with many products designed to resist ignition and minimize flame spread.
| Performance | Testing method | Indexes | Typical |
|---|---|---|---|
| Physical characteristics | |||
| Tensile strength Mpa | GB/T1040 | ≥10.4 | 12.6 |
| Elongation at break % | GB/T1040 | ≥200 | 300 |
| Tensile strength after thermal ageing Mpa | UL224 158℃ ×168hr | ≥7.3 | 9.8 |
| Elongation at break after thermal ageing % | UL224 158℃ ×168hr | ≥100 | 300 |
| Thermal shock resistance | UL224 158℃ ×1hr | Non-sticking | PASS |
| Cold bending resistance | UL224 -30℃ ×1hr | Non-crack | PASS |
| Electrical characteristics | |||
| Breakdown strength kv/mm | GB1418 | ≥1.5 | 1.8 |
| Pressure resistance | UL224 | 1500V Non-breakdown | PASS |
| UL224 | 2000V Non-breakdown | PASS | |
| Volume resistivity Ω﹒cm | GB1410 | 1×10¹⁴ | 1×10¹⁵ |
| Chemical characteristics | |||
| Corrosion resistance | UL224 158℃ ×168hr | PASS | |
| Copper invariability | UL224 158℃ ×168hr | PASS | |
| Flame retardation | UL224 | VW-1 | PASS |
Flame-Retardant Heat Shrink Tubing
Flame-retardant heat shrink tubing is specifically engineered to enhance safety in electrical applications. These products often meet rigorous standards such as the VW-1 flammability test, which requires the tubing to self-extinguish within 60 seconds after flame removal. Many manufacturers offer tubing with limited fire hazard properties, capable of operating in temperatures ranging from -40°C to +105°C. While not completely fireproof, flame-retardant variants significantly reduce the risk of fire propagation, making them crucial for environments where fire safety is paramount.
Material Variations in Tubing
Different materials used in heat shrink tubing offer varying levels of flame resistance and performance characteristics. Polyolefin-based tubing is popular for its balance of flexibility and flame retardance, often incorporating additives to enhance fire resistance. For applications requiring superior flame-retardant qualities, PVDF (Polyvinylidene fluoride) tubing with specific additives is preferred. Some manufacturers also produce halogen-free options designed to produce low smoke and minimal toxic gases when exposed to fire, catering to environments with stringent safety requirements.
Burning Under Extreme Conditions
Despite flame-retardant properties, heat shrink tubing can ignite under extreme conditions or prolonged exposure to direct flames. Non-flame-retardant or lower-grade tubing may burn more easily when subjected to high temperatures. Even flame-retardant tubing can combust if exposed to sufficient heat, as no material is entirely fireproof. This vulnerability underscores the importance of selecting appropriate tubing for specific applications, especially in high-risk environments where fire safety is critical.
Industry Standards for Safety
Industry standards play a crucial role in ensuring the safety and reliability of heat shrink tubing. Aerospace and industrial applications often require compliance with stringent standards such as SAE AS23053 and ASTM D8355, which include rigorous flammability tests to ensure safety in high-risk environments. For general applications, the VW-1 flammability test under UL 1581 is commonly used to assess flame resistance. To meet VW-1 requirements, heat-shrinkable tubing must not allow flame spread to exceed 60 seconds and must self-extinguish within a specified time after the flame source is removed.
