Material Analysis
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Insufficient Heat Seal Strength of Polypropylene Film
Problem Phenomenon
After heat sealing, the seal strength of the film is low, and the seal cracks when stressed.
Insufficient heat seal strength affects the packaging sealability and causes leakage in food packaging films.
Cause Analysis
(1) The heat seal temperature is too low, and the melting is insufficient
(2) The heat seal pressure is insufficient or the time is not enough
(3) The film thickness is uneven, and the heat seal part is too thin
(4) The film surface is contaminated or additives precipitate
(5) The heat seal material is selected improperly
Solution
(1) Adjust the heat seal temperature according to the melting point of polypropylene, generally 10-20°C higher than the melting point
(2) Increase the heat seal pressure to 0.2-0.4MPa, with a heat seal time of 0.5-2s
(3) Ensure the film thickness is uniform, especially at the heat seal part
(4) Control the amount of additives to avoid surface precipitation affecting heat sealing
(5) Use heat seal layer materials (such as LDPE, EVA, etc.) when necessary
Key Takeaway
Insufficient heat seal strength is caused by improper setting of temperature, pressure, or time, and the heat sealing process parameters need to be optimized.
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