From the perspective of raw materials and processes, there are eight reasons for the poor bonding of composite films: incorrect adhesive ratio, improper adhesive storage, diluent contains water, alcohol residue, solvent residue, excessive coating amount of adhesive, insufficient curing time and temperature, and additives.
1. Incorrect adhesive ratio
The ratio of adhesive has been incorrectly weighed, resulting in insufficient curing. In this regard, it is necessary to weigh all materials and record the amount for easy inspection; Secondly, the prepared adhesive should be fully stirred in the correct way to avoid uneven local mixing.
2.Improper adhesive storage
Improper storage of the adhesive results in incomplete sealing of the curing agent, causing it to react with moisture in the air and consume another part. As a result, insufficient content of the curing agent occurs during mixing. Therefore, it is necessary to check the sealing condition of the adhesive before use.
3.Diluent contains water
The diluent is not pure enough and contains excessive water,alcohol makes adhesive proportion imbalance. The storage of the diluent should be sealed with moisture in the air from entering, and the water content of the diluent should be regularly tested.
4. Alcohol residue
The use of alcohol-soluble ink or ink thinner alcohol components are not dried, more residue, so that the reaction with the curing agent, resulting in sticky. Alcohol-soluble ink should use alcohol-soluble adhesive, printing solvent as far as possible not to use alcohol ratio.
5. Solvent residue
There is too much residual solvent in the film during the composite process, and the solvent is wrapped in the adhesive, which hinders the curing. It is necessary to regularly check whether the inlet and exhaust air of the drying system is normal, and control the compound speed when the gluing water is large.
6. Excessive coating amount of adhesive
The adhesive is coated too much, and the film roll diameter is too large, resulting in a slow internal hardening of the adhesive. The adhesive coating should be appropriate and the curing should be sufficient.
7.Insufficient curing time and temperature
The curing temperature is too low, the curing is slow, and the cross-linking is insufficient. Appropriate curing temperature should be selected, curing time should be sufficient, and rapid curing adhesive should be selected if necessary. Insufficient curing time, the temperature can not reach, especially in the high temperature retort pouches, will cause the printing color decoloration or color transfer during high temperature.
8. Additives
The influence of additives in the composite film substrate, such as the additive in PVDC can delay and prevent the cross-linking curing of adhesive, the softener in PVC an react with the NCO group of curing agent, and the plasticizer of soft PVC can penetrate into the adhesive, which will reduce the bonding force and thermal stability, so the use of curing agent should be appropriately increased.
Post time: Jul-10-2023
