The choice of heat sealing temperature for food bags is closely related to the function and thickness of the composite substrate, the type and speed of food bags, and the pressure of hot air, which are the concave and convex factors that affect the heat sealing strength. The starting temperature of the food bag is determined by the viscous flow temperature or melting temperature of the heat-sealing material, and the high temperature of the heat-sealing material should not exceed the decomposition temperature of the heat-sealing material. The temperature between the viscous flow temperature and the decomposition temperature is the heat sealing temperature range of the heat sealing material and is a key factor affecting and controlling the heat sealing quality. The larger the heat-sealing temperature range, the better the heat-sealing performance and the simpler and more stable the quality control.
The heat sealing temperature of the food bag should not be higher than the heat setting temperature of the printed substrate. Otherwise, the heat seal will shrink and wrinkle, reducing the heat seal strength and the impact resistance of the bag. Hot air pressure is provided by a pressure spring on the food bag. The heat sealing pressure is related to the performance, thickness, and width of the food bag. The polar heat-sealing material has a high activation function, and its viscosity is affected by heating, so the heat-sealing pressure is small, preventing the molten material from being squeezed and affecting the heat-sealing effect.