Summary of common issues with packaging bags, covering all problems like damage and warping.

During the packaging bag processing, problems such as damage, brittle sealing, and breakage often occur. Shunxingyuan Packaging, a professional flexible packaging manufacturer, has summarized these common problems and provided detailed answers on how they occur and how to solve them.

 1、 Drop Test: Reasons for Packaging Bag Damage?

Reasons:

Sometimes, when the heat sealing temperature is lower, the heat sealing strength is also lower, but it can still meet customer requirements. However, the packaging bag does not break during the drop test. When the heat sealing temperature is higher, although the heat sealing strength is higher, the packaging bag breaks during the drop test.

This phenomenon indicates that when the heat sealing temperature is higher, under the action of the heat sealing knife pressure, the inner PE film carrying the heat sealing function is melted and squeezed at high temperature, becoming thinner and more brittle, resulting in damage during the drop test.

Solution:

During the bag making process, the appropriate heat sealing temperature and pressure should be adjusted to produce products with excellent comprehensive performance.

2、 What to do about brittle and broken seals?

Reasons:

1. Heat sealing temperature is too high.

2. Excessive pressure.

3. Heat sealing time is too long.

4. The edge of the upper sealing device is too sharp, or the polytetrafluoroethylene covering is damaged.

5. The silicone rubber at the bottom seal is too hard.

6. During the compounding and curing process, part of the adhesive penetrates into the film. Due to the penetration of the adhesive, the toughness (impact resistance) of the substrate decreases, and the brittleness increases.

7. After cooling and placement, the heat sealing strength of the plastic composite packaging bag increases, and there is also a tendency to become brittle.

Solution:

1. According to the heat sealing characteristics of the inner sealing layer material, select the appropriate processing temperature, pressure, and heat sealing time.

2. Improve the surface condition of the upper heat sealing knife to make the surface of the sealing device smooth.

3. Ensure the polytetrafluoroethylene cloth is well covered.

4. Select silicone rubber pads with appropriate hardness.

3、 What to do about static electricity at the seal?

During secondary processing, 3% of food-grade anti-static agent can be added to the inner PE film to avoid this problem. Therefore, flexible packaging companies should fully understand the product characteristics and automatic filling production line characteristics of customers when accepting customer orders, so that they can be targeted and better meet customer requirements.

4、 What to do about bag warping after heat sealing?

Reasons:

1. Inconsistent thickness of the composite film.

2. Heat sealing temperature is too high or heat sealing time is too long.

3. The running trajectory of the composite film is not straight in the longitudinal heat sealing knife section.

4. Insufficient cooling.

5. Insufficient curing time.

6. The surface substrate film has poor heat resistance.

7. Improper control of the tension matching of the composite substrate during the compounding process, resulting in residual stress after curing and shaping, especially when the composite film is thinner.

Solution:

1. Adjust the floating roller tension.

2. Select an inner sealing substrate with low-temperature heat sealing properties.

3. Adjust the heat sealing temperature to an appropriate temperature.

4. Sufficient cooling.

5. Sufficient curing.

6. Re-select the surface substrate film.

7. Adjust the tension of each part of the composite processing equipment to make the shrinkage rate of the two composite substrates as equal as possible.

5、 Poor heat sealing strength?

1. Influence of heat sealing materials

Different types of heat sealing materials have different heat sealing strengths, such as PP, PE, and EVA. Products of the same type of film with different polymerization methods also have different heat sealing strengths. The thickness and uniformity of the material will also affect the heat sealing strength. Different processing methods of the heat sealing layer, such as blown film and cast film, also affect the heat sealing strength. If the film is stored for too long, the amount of exudates increases, and the heat sealing strength is poor after corona treatment. Hygroscopic materials absorb moisture, the heat sealing surface delaminates, and the peel strength decreases.

2. Influence of composite film processing technology

The printing ink has poor temperature resistance or inappropriate additives are added to the ink. At high temperatures during bag making, the printing layer delaminates, and the heat sealing strength decreases. The heat sealing edge should be designed without patterns as much as possible. The selection of adhesive in the composite process is also very important. The rationality of the ratio and viscosity of the adhesive will affect the sealing strength. In the extrusion composite or coating process, the processing temperature is high, the degree of material surface oxidation is large, and the amount of carboxyl groups generated increases, which is not conducive to heat sealing.

3. Influence of bag making process

The heat-sealed edges are not cooled enough, and the shaping is insufficient, which cannot eliminate internal stress, affecting strength and appearance. It should be checked in time, and the cooling water circulation system should be strengthened. The more heat sealing times, the higher the heat sealing strength. The number of longitudinal heat sealing times depends on the ratio of the effective length of the longitudinal welding knife to the bag length; the number of transverse heat sealing times is determined by the number of combinations of the transverse heat sealing device of the machine. Good heat sealing requires at least two heat sealing times.

6、 Spots and bubbles on the sealing edge?

1. Material factors. For example, hygroscopic materials such as PT and NY easily absorb moisture during storage, and easily produce bubbles and air spots during high-temperature bag making. In addition, because the composite adhesive is not yet fully cured, it is not temperature-resistant enough and has poor peel strength during high-temperature heat sealing, and it is also easy to delaminate and produce air spots.

2. Air spots are easily produced when the heat-sealing edge is wider. The pressure should be adjusted, the gap should be increased, and the trapped air should be squeezed out. Fluctuations in the movement of the film will trap air. It should be cleaned before cutting, and the plates should be properly clamped before entering the heat-sealing knife.

3. Improper bag making control, such as deformation of the silicone rubber plate after long-term use, damage to the high-temperature cloth, and dirt on the heat-sealing knife. Inappropriate and uncoordinated process parameters such as bag making speed, temperature, and pressure will also produce air spots.

7、 What should I do if the film length is insufficient or the width deviation is too large during slitting?

Reasons:

This is caused by incorrect rewinding counting or insufficient length of the slit film, and incorrect equipment positioning. To meet the user's needs for a certain length of film roll, operators can usually obtain the rewinding length from the data displayed on the rewinder.

However, in production, situations such as film breakage and scratching of part of the film on the surface of the large-diameter film roll often occur. If the calculation and cutting are performed according to the marked length, and it is found that the length is insufficient and cannot be spliced until the final slitting, then the entire vehicle product cannot become a finished product, especially for slitting machines with a width of 1 meter or more, the economic loss is even greater.

Solution:

To avoid this situation, the length and diameter of the large-diameter film roll with the same model, specifications, and process should have a certain corresponding relationship. As long as the measured diameter data is compared with the rewinding length after being put on the machine, it can be roughly known whether the length of the film roll meets the requirements. If the difference between the two is large, pay attention to the splicing length during cutting to avoid insufficient length.