What affects the sealing of plastic bottles

The sealing of plastic bottles is affected by a variety of factors, the following is a specific analysis:
Plastic bottle itself factors
Material: Plastic bottles of different materials have different thermal stability, flexibility and chemical properties. Such as PET (polyethylene terephthalate) bottle, good thermal stability, suitable for heat sealing, but the heat sealing temperature and time requirements are more strict; PP (polypropylene) bottle has good flexibility, but the heat sealing difficulty is relatively high, and appropriate heat sealing parameters are needed to ensure the sealing quality.
The shape and size of the bottle mouth: the shape of the bottle mouth, such as round, square or shaped, as well as the diameter of the bottle mouth, wall thickness and other dimensional parameters will affect the sealing effect. The bottle mouth is irregular and the size deviation is large, which will lead to the sealing film and the bottle mouth can not fit well, and the sealing is not strict.
Bottle structure: The overall structure and strength of the bottle will also indirectly affect the sealing. If the structure of the bottle is unstable, it is easy to deform during the sealing process, so that the seal is stressed unevenly, affecting the sealing and integrity of the seal.
Sealing material factor
Type: Common sealing materials are plastic film, aluminum foil, etc. Plastic film sealing materials have different materials and thickens, such as PE (polyethylene) film is soft but the sealing performance is relatively weak, and PA (polyamide) film has high strength and good barrier property, but the cost is high. The thermal sealing performance of different materials is different, and it is necessary to choose according to the material and use requirements of plastic bottles.
Quality: The quality of the sealing material is directly related to the sealing effect. Poor quality sealing materials may have uneven thickness, poor surface flatness, and high impurity content, which will lead to unstable sealing and lax sealing.
Sealing process factor
Temperature: The heat sealing temperature is a key factor affecting the sealing quality. The temperature is too low, the sealing material can not be fully melted, can not be well combined with the plastic bottle, resulting in poor sealing; The temperature is too high, will make the sealing material overheat decomposition, carbonization, damage the integrity of the seal, may also make the plastic bottle mouth deformation.
Pressure: The pressure applied during the sealing process should be moderate. The pressure is too small, the sealing material and the bottle mouth can not be fully contacted and fused, there will be air bubbles, cracks and other sealing problems; Excessive pressure may deform the mouth of the bottle and even damage the plastic bottle, especially for thin-walled plastic bottles or soft plastic bottles, pressure control is more important.
Time: the heat sealing time is too short, the sealing material is not fully melted and bonded; The heat sealing time is too long, which will cause the sealing interface to overheat, affecting the sealing quality and the performance of the plastic bottle.
Environmental factor
Humidity: When the ambient humidity is high, the surface of the plastic bottle and the surface of the sealing material may absorb water, affecting the heat sealing effect, and causing problems such as bubbles and delamination at the seal. At the same time, humidity may also affect the performance of the sealing material, making it soft or sticky, which is not conducive to the sealing operation.
Temperature: the ambient temperature is too low, which will make the plastic bottle and sealing material hard and brittle, increase the difficulty of sealing, and prone to sealing cracking and other problems; The ambient temperature is too high, may make the sealing material soften in advance, affect the sealing precision and quality.
Equipment factor
Equipment performance: The performance and accuracy of the sealing equipment are crucial to the quality of the sealing. If the heating element of the heat sealing equipment is aging and the temperature control is inaccurate, the heat sealing temperature will be unstable; The accuracy of the transmission system of the sealing machine is poor, which will make the pressure in the sealing process uneven or the sealing speed unstable, affecting the sealing effect.
Equipment maintenance: If the equipment is not cleaned, maintained and repaired in time after long-term use, there will be problems such as parts wear and dirt accumulation. These problems will affect the normal operation of the equipment and the sealing quality, such as the dirt on the hot sealing die will lead to the uneven heat sealing temperature, so that the sealing appears locally unstable.