1. Temperature range and characteristics
Starting shrinkage temperature: about 65°C (film begins to soften and shrink slightly).
Optimum shrinkage temperature: usually 80°C–110°C, at which the shrinkage effect is uniform and controllable.
Upper limit temperature: exceeding 120°C may cause excessive shrinkage, deformation or decomposition (PVC decomposition releases hydrogen chloride gas).
2. Influencing factors
Plasticizer content: Plasticizers (such as DOP, DOA) will reduce the glass transition temperature (Tg) and make the shrinkage temperature lower.
Film thickness: thicker films may require higher temperatures or longer times.
Processing methods:
Hot air shrinkage: commonly used temperatures are 90°C–110°C, suitable for fast packaging.
Steam/hot water shrinkage: lower temperatures (70°C–90°C), more uniform shrinkage (such as beverage labels).
Infrared heating: precise temperature control, suitable for high-precision shrinkage (such as electronic component packaging).
3. Key points of temperature control
Preheating: Avoid direct high temperature shock. Preheat to 60°C–70°C to reduce stress.
Uniform heating: Uneven temperature will cause excessive or insufficient local shrinkage.
Cooling and shaping: Rapid cooling (such as cold wind or water mist) is required after shrinkage to prevent rebound.
4. Precautions
Avoid overheating: Over 140°C will cause PVC to decompose and produce harmful gases.
Formula differences: Flame retardant, weather-resistant and other modified PVC may require temperature adjustment.
Equipment calibration: Regularly calibrate the heating equipment to ensure temperature accuracy.
