Examples of common faults in the hottest coating c

Examples of common faults in coating and compounding and their solutions

causes of poor peel strength:

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 are adhered, resulting in the decrease of 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 composite process, if the melt index of the selected resin is low and the fusibility is poor, it cannot bond well with the coated substrate, which will reduce the peel strength

4. the additives in the resin (especially the smoothing agent) will adversely affect the peel strength of the extruded composite film

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

6. the resin temperature is low, and the resin surface oxidation is not sufficient, which is not conducive to the wetting and penetration of the molten resin on the coated substrate, thus affecting the peel strength of the extruded composite membrane

7. In the process of extrusion, the size of air gap also has a great influence on the peel strength of the extruded composite film. The air gap is too small, and the surface oxidation of the resin is not sufficient, 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 is too low when compounding, it will also cause the peel strength to decrease

8. the composite pressure is small, and the bonding between the molten resin and the substrate is not tight, which reduces the peel fastness

9. the surface temperature of the cooling steel roller is too high, and the cooling 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 of constant speed of the main motor of extrusion, the faster the linear speed of the composite is, the thinner the composite layer is, the faster the temperature of the molten resin decreases, and the adhesion with the substrate decreases, resulting in the decrease of peel strength

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

13. insufficient drying of primer, residual solvent or water, resulting in stripping of extruded composite film, in which supermarkets and other retail places remain below 300000 tons, and the separation strength is reduced

solution:

1. Replace the coated substrate or re corona the substrate to ensure that its surface tension is above 4.0 x n/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 coated substrate is clean and clean

3. replace the resin with appropriate melt index

4. In the extrusion compounding process, LDPE resin of extrusion coating grade without or with a small amount of smoothing 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. Appropriately 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 composite 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 extruded coating to improve the peel strength

11. control the production speed according to the actual situation

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

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

causes of wrinkle failure of composite film:

1. The thickness of substrate is uneven, and the thickness difference is too large

2. The substrate position is skewed, resulting in wrinkles in the composite film, and with the accumulation of skewness, the degree of wrinkles will increase accordingly

3. if the substrate is a thin film material that is easily affected by humidity, many new materials and technologies should be transported to raw materials (such as nylon film), and moisture absorption occurs, which is easy to wrinkle in the extrusion process

4. the tension setting and control are improper, and the tension of each part is uncoordinated and mismatched

5. the composite pressure is set improperly

6. the axis between the silicone rubber press roll and the cooling steel roll is not parallel

7. the surface of the guide roller is not clean, with foreign matters adhered, or the surface of the guide roller is uneven, with pits, scratches, bumps and other phenomena

solution:

1. Replace the substrate to ensure that the thickness of the substrate is uniform

2. Adjust the position of the base material to avoid skewing during transmission

3. preheat and dry the substrate, or replace the substrate without moisture absorption

4. adjust the tension of unwinding and rewinding to make the tension of each part adapt and match each other

5. adjust the pressure of the compound roll to an appropriate size according to the actual situation

6. adjust the relative position between the silicone rubber press roll and the cooling steel roll to keep them parallel

7. clean the surface of the guide roller and replace the damaged guide roller to ensure that the surface of the guide roller is flat, smooth and clean

causes of uneven coating thickness:

1. The melt index of the resin is too high and the fluidity is too strong

2. The resin density is too high, and the thickness of the molten resin film is difficult to control

3. improper temperature control of extruder and uneven die head temperature (this is the main reason for uneven coating thickness)

4. uneven die gap leads to inconsistent thickness of molten resin layer extruded from the die

5. There are foreign matters attached at the die mouth, so that the extrusion coating amount at this part is less than that at other parts, so that the coating thickness at this part is correspondingly thinner

6. the composite pressure is uneven and cannot maintain a constant value

7. the surface of the rubber press roll is aging, with inconsistent hardness, uneven surface, pits, scratches, etc

8. the compound linear speed cannot be kept constant. The coating thickness of the extruder can be controlled by adjusting the compound linear speed. If the extruder breaks down and the compound linear speed changes continuously, the coating thickness will change continuously

9. the screw speed of the extruder changes. When the compounding speed is constant, increasing the screw speed of the extruder will increase the coating amount and the coating thickness. If the screw speed of the extruder changes constantly, the coating amount and coating thickness change constantly, resulting in uneven coating thickness

solution:

1. Replace the resin with appropriate melt index

2. Replace the resin with appropriate density

3. adjust the temperature of the die head to ensure that the temperature of each part is uniform and constant

4. adjust the resulting gap between die openings to make it even

5. Remove foreign matters attached locally to the die

6. adjust the compound pressure to ensure its uniformity

7. replace the rubber pressing roller and ensure its quality, especially the uniformity and consistency of the hardness of the rubber layer on its surface

8. adjust and control the compound linear speed of the extruder to keep it constant according to the actual situation

9. adjust and control the screw speed of the extruder according to the actual situation

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