Poor peel strength failure reasons:

1. The surface tension of the substrate is low, the surface treatment effect is poor, and the surface tension is uneven, which affects the adhesion of the melt-extruded resin on the surface, resulting in low peel strength and uneven peel strength.

2. The surface of the substrate is not clean, and dirt such as dust and grease adheres, resulting in a decrease in the bonding strength between the molten resin and the surface of the film.

3. The resin melt index (MI) is low. Generally, the higher the melt index of the resin, the better its fluidity and the greater the adhesion. Therefore, in the extrusion compounding process, if the melt index of the selected resin is low and the fusion is poor, it cannot be well bonded to the coated substrate, resulting in a decrease in peel strength.

4. Auxiliaries (especially slip agents) in the resin will adversely affect the peel strength of the extruded composite film.

5. The barrel temperature and die temperature of the extruder are too low, the resin plasticization is poor, and the molten resin cast from the die cannot be well compounded with the coated substrate, which reduces the peel strength.

6. The resin temperature is low and the resin surface is not sufficiently oxidized, which is not conducive to the wetting and penetration of the molten resin on the coated substrate, thereby affecting the peel strength of the extruded composite film.

7. In the extrusion lamination process, the size of the air gap also has a great influence on the peel strength of the extrusion lamination film. If the air gap is too small, the resin surface is not sufficiently oxidized, which makes the composite strength worse; if the air gap is too large, the heat loss of the molten resin is large, and the temperature during composite is too low, which will also cause the peel strength to drop.

8. The compound pressure is small, and the bonding between the molten resin and the substrate is not tight, which reduces the peeling fastness.

9. If the surface temperature of the cooling steel roll is too high, the cooling and setting effect is not good, which will reduce the composite fastness; if the surface temperature of the cooling steel roll is too low and the cooling speed is too fast, the composite strength will also be reduced.

10. The thickness of the extruded composite layer is too thin, resulting in a decrease in peel strength.

11. Under the condition that the speed of the extrusion main motor remains unchanged, the faster the composite line speed is, the thinner the composite layer is, the faster the temperature of the molten resin drops, and the adhesive force with the substrate decreases, resulting in a decrease in peel strength.

12. The primer (AC agent) is of improper type or poor quality.

13. Insufficient drying of primer and residual solvent or water, resulting in reduced peel strength of extruded composite film.

Solution:

1. Replace the coated substrate or re-corona treat the substrate to ensure that its surface tension is above 4.0 x 10-2N/m, and the corona treatment effect should be uniform.

2. Clean the surface of the substrate or replace the substrate to ensure that the surface of the substrate to be coated is clean and clean.

3. Replace resin with appropriate melt index.

4. In the extrusion compounding process, the extrusion coating grade LDPE resin containing no or a small amount of slip agent is selected.

5. Adjust and control the temperature of each section of the extruder according to the production situation to ensure the composite strength.

6. Properly increase the resin temperature to fully oxidize the resin and improve its wettability and adhesion on the surface of the substrate.

7. Adjust the size of the air gap according to the actual situation.

8. Adjust the compound pressure appropriately according to the specific situation.

9. Control the temperature of the surface of the cooling steel roll below 60c.

10. Appropriately increase the thickness of the extrusion coating to improve the peel strength.

11. Control the production speed according to the actual situation.

12. Replace the primer with the appropriate type and good quality to ensure strong adhesion.

13. Appropriately reduce the composite line speed, increase the drying temperature and ventilation, ensure that the primer is fully dried and improve the peel strength.