How much do you know about quality control of food packaging bags?

Currently, much research on how to extend product shelf life has shifted from methods focusing on the product itself to the packaging system. Food packaging bags For example, good oxygen barrier properties, water barrier properties, and airtightness of the packaging are essential requirements. These requirements can be verified by testing the oxygen transmission rate, water vapor transmission rate, overall sealability, and heat sealing performance of the food packaging bag.

Oxygen transmission rate

Oxygen affects food in four main ways: color change, flavor change, oil/fat change, and microbial change. Mastering the oxygen transmission rate and permeability coefficient of food packaging materials can effectively help companies choose packaging materials and provide scientific basis for maintaining product quality and improving product preservation.

Water vapor transmission rate

If the product's moisture permeates from the inside of the packaging film in the form of water vapor, or if the product absorbs water vapor permeating from the outside of the packaging, the flavor, texture, and content of the product will change. Therefore, it is necessary to accurately grasp the water vapor transmission rate and permeability coefficient of plastic film packaging materials. The principle of water vapor transmission rate testing is to maintain a constant saturated vapor pressure on one side of the plastic film sample at a certain temperature, and keep the other side dry. Saturated water vapor permeates the sample into the dry side, and the water vapor transmission rate and permeability coefficient of the sample are determined by measuring the change in the amount of distilled water evaporation in the permeation cup over time. The water vapor transmission rate and permeability coefficient are extremely important for maintaining product quality and preventing the natural loss of quantitative products.

Overall sealability

If the packaging's seal is poor, oxygen and water vapor can directly enter the packaging, causing the food to degrade and deteriorate. There are various methods for sealability testing. The most common method is to use a sealability tester, using the vacuum principle, according to national standards, at -30kpa, -50kpa, -70kpa, and -90kpa for a certain period of time, observing whether there is any leakage in the packaging bag during the test and the recovery of the packaging bag after the test. Manufacturers must effectively measure the sealing performance of the packaging under different pressures and times to better control the airtightness of the packaging and thus extend the shelf life of the product.

Heat sealing performance

Heat sealing performance is an important parameter affecting the overall sealability of the packaging. If the heat sealing parameters are not set properly, the heat sealing area is weak, and under the impact of the contents or under external pressure, the bag is easily broken at the heat sealing area. The three major factors of heat sealing process are heat sealing temperature, pressure, and time, mainly temperature. Different heat sealing conditions are required depending on the plastic packaging material and the movement state of the material bag. The three must be coordinated to obtain good heat sealing quality, thereby ensuring the overall packaging sealability.

Reasons for damage to packaging bags in drop tests?

Reasons: Sometimes, when the heat sealing temperature is low, the heat sealing strength is low, but it can still meet customer requirements. However, the packaging bag does not break during the drop test. When the heat sealing temperature is high, although the heat sealing strength is high, the packaging bag breaks during the drop test. This phenomenon indicates that when the heat sealing temperature is high, 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 brittle, resulting in damage during the drop test.

Shunxingyuan Packaging Solution: During the bag making process, adjust the appropriate heat sealing temperature and pressure to produce products with excellent comprehensive performance.

What to do about brittle and broken seals?

Reasons:

(1) The heat sealing temperature is too high.

(2) Excessive pressure.

(3) The 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 placing, the heat sealing strength of the plastic composite packaging bag increases, and there is also a tendency to become brittle.

Shunxingyuan Packaging Solution:

(1) Select appropriate processing temperature, pressure, and heat sealing time according to the heat sealing characteristics of the inner sealing layer material.

(2) Improve the surface condition of the upper heat sealing knife to make the surface of the sealing device flat.

(3) The polytetrafluoroethylene cloth is well covered.

(4) Select silicone rubber pads with appropriate hardness.

What to do about static electricity at the seal?

Reasons:

External factors such as friction or the action of various forms of energy such as kinetic energy, potential energy, thermal energy, and chemical energy can cause an imbalance between positive and negative charges in atoms.

Shunxingyuan Packaging Solution: During secondary processing, add 3% of food-grade anti-static agent to the inner PE film to avoid this problem. When receiving customer orders, Shunxingyuan Packaging will fully understand the characteristics of the customer's products and the characteristics of the automatic filling production line to achieve targeted results and better meet customer requirements.

What to do about warped bags after heat sealing?

Reasons:

(1) Inconsistent thickness of the composite film.

(2) The heat sealing temperature is too high or the 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 tension matching control of the composite substrate during lamination results in residual stress after curing and shaping, especially when the composite film is thin.

Shunxingyuan Packaging Solution:

(1) Adjust the tension of the floating roller.

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

(3) Adjust the heat sealing temperature to a suitable temperature.

(4) Cool thoroughly.

(5) Fully cure.

(6) Re-select the surface substrate film.

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

Mottling and bubbles on the edges?

(1) Material factors. For example, hygroscopic materials such as PT and NY easily absorb moisture during storage, and easily produce bubbles and 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, which can also easily cause delamination and spots.

(2) When the heat-sealed edge is wider, spots are easily generated. The pressure should be adjusted, the gap should be increased, and the trapped air should be squeezed out. Fluctuations in film movement will trap air, which should be removed before cutting. 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 spots.

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