The packaging bag quality is not good, recommend a reliable supplier

Many manufacturers often receive customer complaints about product quality. However, when looking for reasons from raw materials and product technology, the problem is often with the packaging. If the packaging bags are of poor quality, how do you choose a reliable supplier?

Shunxingyuan Packaging, a professional flexible packaging manufacturer, believes that regardless of the packaging issue, strengthening packaging quality control is an effective method to prevent quality accidents from happening again.

Shunxingyuan High-Quality Garment Bags Series

Shunxingyuan High-Quality Hardware Bags Series

Shunxingyuan High-Quality Cosmetic Bags Series

Shunxingyuan High-Quality Hook Bags Series

Shunxingyuan High-Quality Concealed Zipper Bags Series

Shunxingyuan High-Quality Food Bags Series

To stay ahead of quality issues, ensuring product packaging quality requires eliminating product packaging accidents from the source. Shunxingyuan Packaging explains how we control packaging quality from the source, from raw material selection, printing, lamination, slitting, and bag making. After reading this, you'll understand what to do.

I. Raw Material Quality Control Points

1. Film Appearance

First, check the film's flatness, thickness, and whether there are any sawtooth shapes at both ends. A film thickness within ±5μm is generally considered a qualified product. If the thickness difference is large, it will cause fluctuations in the printing pattern registration and unevenness in the lamination. Visually inspecting the sawtooth shape at both ends of the film will cause printing and lamination breaks, resulting in a large number of rejects. Common methods for detecting film thickness are thickness gauges and visual inspection.

The static and dynamic friction coefficients of the original film should be tested using a film friction coefficient instrument.

2. Film Corona Value

The corona value directly affects the ink adhesion and peel strength after lamination. (Corona pen, self-prepared corona solution can be used)

Corona values required for various film substrates

Self-prepared corona solution formula

3. Selection and Application of Film Materials

When making retort pouches, PA film should choose A-grade products. In the production of PA film, there are step-by-step stretching and simultaneous stretching methods. The step-by-step stretching method is to stretch the longitudinal or transverse direction first, and then stretch the other direction, while the simultaneous stretching method stretches the transverse and longitudinal directions simultaneously, so the shrinkage rate is basically the same when encountering temperature. During the retorting process, the different shrinkage ratios of PA often cause the retort pouch to curl, resulting in a warped corner phenomenon.

AL film: Density is 2.67g/cm3, excellent barrier properties, poor tensile strength, and easy to break. AL has the characteristic that one side has an extremely high corona value, while the other side only has about 38 dynes.

The most important factor determining the quality of AL is that the oil used for cooling during aluminum foil production must be cleaned, otherwise it will greatly affect the lamination strength. A cotton swab can be dipped in distilled water or tap water and wiped on the aluminum foil surface at a 45° angle. If the water spreads evenly, it proves that the oil is well treated. Conversely, if the water is in a water droplet shape on the aluminum foil, it can be determined that there is oil on the aluminum foil, which is a defective product.

Aluminum foil not cleaned

Metallized film: The density is basically the same as the metallized base material, with little change. Mainly check: adhesion strength of metallization, pinholes, and uniformity of the aluminum layer.

4. Other Raw Material Quality Control Methods

Film Additives:

Place the film in a curing room at 50-60℃ for about 8-20 hours, and test the film's friction coefficient. If the friction coefficient increases significantly compared to before curing, it indicates that the additive content is high. This method can only detect the presence or absence of additives, not the amount of additives. (Film friction coefficient instrument can be used here)

Solvent Purity Test:

Purity and water content of solvents such as ethyl acetate, toluene, n-propyl acetate, isopropyl alcohol, and butyl acetate (using gas chromatography).

Simple Viscosity Test of Ink and Glue:

Dilute to a certain ratio, fill a No. 3 Zahn cup with ink or glue, and judge the viscosity by the time it takes to flow out. The longer the flow time, the greater the viscosity, and vice versa (the flow hole of the No. 3 cup must be cleaned).

Simple Solid Content Test:

Open the ink or glue bucket, take a certain amount of ink or glue and pour it into a beaker, do not cover it, put it in a 50℃ curing room, cure for 24 hours, and then divide the weight of the ink or glue at this time by the original weight, which is the so-called solid content, because all the solvents are basically volatilized in the curing room. (Measuring cup, beaker)

II. Printing Process Quality Control Points

Surface Visual Inspection:

Accurate registration, no scratches, clear printing text and patterns. Neat winding, tension, and whether there are any broken threads, etc. (Visual inspection)

Ink Dilution Viscosity Before Machine Operation:

Adjust the appropriate ink viscosity according to the machine speed, drying effect, etc. (No. 3 cup, stopwatch)

Ink adhesion can be tested using 3M tape at a 45° angle. The best adhesion is when the ink does not transfer. (3M tape)

Detection of Residual Solvent in Ink:

A gas chromatograph should be used to detect the residual amount of each solvent.

III. Lamination Process Quality Control Points

Prediction Method of Adhesive Amount:

Adhesive amount = 1/5 × glue concentration × glue density × mesh depth.

Adhesive amount detection:

After applying the adhesive, take three samples each from the left, middle, and right of the unlaminated printing film (blank film) that has not entered the laminating roller. Weigh them and subtract the weight of the original uncoated film. Finally, take the average value. (Using a 0.0001g balance)

Visually inspect the laminated film for bubbles, white spots, etc. on the surface. (Visual inspection)

Testing the tension of the laminated film:

On the laminated film between the winding and laminating rollers, make a cross-shaped cut with a blade to observe the curling direction of the laminated film at the cut. If it curls towards the inner film, it indicates that the inner film tension is high, and the inner film tension should be reduced accordingly. Conversely, reduce the tension of the outer film. Mismatched tension in the laminated film can also cause tunneling and wrinkling. (Visual inspection)

Testing the heating and ventilation of the drying channel on the laminating machine. A thermometer can be used to check the temperature error, and an anemometer can be used to check the air speed of the inflow and outflow, or a thin film can be used at both ends of the drying channel of the laminating machine. Observe whether the film is blowing inward or outward. If it is outward, it indicates that the inflow is greater than the outflow. The outflow can be adjusted to increase, and the inside of the drying channel should be kept as close to a vacuum state as possible. (Anemometer)

The peel strength and heat sealing strength of the cured laminated film must be tested on a film tensile tester to obtain the corresponding peel data. (Film tensile tester)

Residual solvent in the laminated film:

A gas chromatograph is used to detect the amount of residual solvent.

Coefficient of friction of the laminated film:

After curing, a film friction coefficient tester must be used to obtain the required data.

Boiling and steaming of the laminated film:

After making the laminated film into bags and filling them with contents, after vacuuming, perform the corresponding boiling and steaming tests (for bubbles, delamination, peel strength, etc.) to determine whether the requirements or standards are met. (Vacuum machine, pressure cooker, film tensile tester)

IV. Quality requirements for slitting process

Ensure that the cross-section is flat, the tension is moderate, and there is no bursting. (Visual inspection)

V. Quality requirements for bag making process

Bag dimensions, heat sealing position (ruler), and bag flatness can be visually inspected, and heat sealing strength can be tested using a film tensile tester.

VI. Special testing process for special composite bags

Boiled packaging bags:

The bag should be filled with objects or water (the amount of water or other liquid should be controlled to 1/2 or 1/3 of the bag volume) and boiled at 100℃ for 40 minutes without bubbles or delamination.

For steamed bags, after filling and vacuuming, put them into a pressure cooker at 121℃ or 135℃ for 20-40 minutes of high-temperature sterilization without delamination or bubbles. (Pressure cooker)

The quality of packaging bags is affected by many external factors, so Many packaging bag manufacturers cannot provide high-quality packaging bag products. 。 Therefore, choosing a high-quality professional flexible packaging manufacturer, Shunxingyuan Packaging, is the most powerful guarantee and the most effective way to prevent product quality accidents.

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