How To Solve Poor Heat Seal Strength?

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In food packaging, heat sealing has a great influence on the material, the type of heat sealing material is different, and the heat sealing strength is different:

The heat seal strength of PP, PE and EVA is inconsistent. The different densities in PE and the heat seal strength of different polymerization methods are inconsistent. The thickness and thickness uniformity of the material also affect the heat seal strength.

 

Different processing methods of the heat seal layer, such as blown film, cast film, etc., all affect the heat seal strength.

 

There are many additives for the heat seal layer material. When the melting point of the additive is low, the removal is much, the heat sealability is decreased, the storage time of the film is too long, the precipitates are increased, and the heat seal strength is poor after corona treatment.

 

The hygroscopic material absorbs moisture, the hot cover is delaminated, and the peel strength is lowered.

 

In addition, printing composite processing also has a certain impact on the heat seal strength:

The printing ink has poor temperature resistance, and the printed layer is delaminated at a high temperature of the bag. Or the additive in the ink is improperly caused to separate the composite layer at a high temperature, and the heat seal strength is lowered. Heat sealing should be designed as ink-free printing.

 

The adhesive in the dry composite is not cured completely, or the adhesive ratio is improper, and the composite film is sticky, resulting in a decrease in the seal strength.

 

The MDI type polyisine ester in the adhesive migrates to the inner film surface through the inner film to react with water vapor to form a poly-de-heat sealant layer. The inner film quality is poor and the adhesive ratio or the selection is wrong. occur.

 

In the extrusion compounding or coating process, the processing temperature is high, the air gap is long, the degree of oxidation of the surface of the material is large, and the amount of generation of the wave base is increased, which is disadvantageous for heat sealing.

 

The additive amount of the extruded material is <0.12%, and the processing temperature

 

The bag making process also affects the heat seal strength:

Insufficient heat sealing pressure makes it difficult to fuse the hot cover to one piece and it is difficult to remove air from the interlayer.

 

The heat sealing temperature is not appropriate. The heat sealing temperature should be set according to the material, processing speed, material thickness, and surface material.

 

Heat sealing time is not enough. Under the same heat sealing temperature and pressure, the heat sealing time is long, the heat sealing layer is more fully fused, and the bonding is stronger, but the heat sealing time is too long, and the film is easy to shrink, which affects the edge sealing.

 

Insufficient cooling, insufficient sealing of the seal after heat sealing, insufficient setting, can not eliminate internal stress, affect strength and appearance, should check and strengthen the cooling water circulation system.

 

The more heat seal times, the higher the heat seal strength, the number of longitudinal heat seals depends on the ratio of the effective length of the longitudinal weld to the length of the bag; the number of transverse heat seals is determined by the number of sets of transverse heat seals of the machine. A good heat seal requires at least two heat seals.

 

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By | 2019-09-18T07:41:43+00:00 September 18th, 2019|Blog|Comments Off on How To Solve Poor Heat Seal Strength?

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