The testing method for heat sealing strength of food packaging bags is similar to that of general packaging bags, but there are some special requirements and precautions for food packaging in terms of sample processing, mainly including the following:

1、 Tensile testing method

Principle: Apply vertical tensile force to the heat sealed part of the food packaging bag at a specified speed to separate the heat sealed part, and measure the maximum tensile force that the heat sealed part can withstand to measure the heat sealing strength. It is recommended to use the Paratronix ETT-A Multipurpose Tester for testing.

Test steps

Sample preparation: Cut a sample with a width of 15mm ± 0.1mm and a length of not less than 100mm from the food packaging bag along the heat sealing direction. If the packaging bag has multiple layers of structure, it should be ensured that the sample contains all heat sealing layers. To avoid the influence of food residues on testing, the surface of the sample should be cleaned thoroughly, and at least 5 samples should be taken.

Clamping the specimen: Vertically clamp the specimen onto the fixture of the tensile testing machine, with the heat sealing part located at the center of the fixture, ensuring that the clamping is firm and does not damage the specimen.

Setting parameters: Based on the material and thickness of the packaging bag, the stretching speed is generally set to 300mm/min ± 50mm/min.

Record data: When the heat sealing part is completely separated, record the maximum tensile force value displayed by the tensile testing machine.

Result calculation: Heat sealing strength (N/15mm)=maximum tensile value (N)/specimen width (15mm), take the average as the test result.

2、 Peel off test method

Principle: Peel off the two layers of material that heat seal the food packaging bag at a certain speed, measure the force required during the peeling process, and reflect the heat sealing strength. It is recommended to use the Paratronix ETT-A Multipurpose Tester for testing.

Test steps

Sample preparation: Cut a sample with a width of 25mm ± 0.5mm and a length of 100mm~150mm from the food packaging bag. If the packaging bag has patterns or coatings, attention should be paid to avoiding interference with the test, and the number of samples should not be less than 5.

Clamp the sample: Peel off one end of the heat sealed part of the sample by 20mm to 30mm, and clamp it on the upper and lower fixtures of the peeling testing machine, so that the heat sealed part coincides with the centerline of the fixture.

Setting parameters: The peeling speed is usually set to 300mm/min ± 50mm/min, and the testing machine is started for testing.

Record data: Record the maximum peeling force value during the peeling process.

Result calculation: Heat sealing strength (N/25mm)=maximum peel force value (N)/specimen width (25mm), calculate the average value as the final result.

3、 Tear test method

Principle: Apply tearing force to the heat sealed area of food packaging bags, causing tearing at the heat sealed area. Measure the maximum force required to tear the heat sealed area to evaluate the heat sealing strength. It is recommended to use the Paratronix ETT-A Multipurpose Tester for testing.

Test steps

Sample production: Cut a sample with a width of 50mm ± 1mm and a length of 100mm~150mm from the food packaging bag, and make a 20mm ± 1mm long cut in the middle of one end of the heat sealed area, paying attention to the neatness of the cut.

Clamp the specimen: Clamp the uncut end of the specimen onto the fixture of the tear testing machine, with the cutting direction perpendicular to the tensile direction, and clamp the other end with the lower fixture.

Setting parameters and testing: Set the stretching speed to 100mm/min ± 10mm/min, start the testing machine and record the maximum tear force value.

Result calculation: Heat sealing strength (N/50mm)=maximum tear force value (N)/specimen width (50mm), take the average to determine the heat sealing strength.

4、 Voltage withstand test method

Principle: Fill a food packaging bag containing a certain analog substance (such as air, water, or food analogues) with a certain pressure of gas or liquid to expand the packaging bag. Observe the condition of the heat sealing part under pressure to determine the heat sealing strength. Paratronix LT-03A Leak and seal strength tester is used for testing.

Test steps

Sample selection and processing: Select a complete food packaging bag, fill it with an appropriate amount of simulant, and seal the opening. If the simulated object is a liquid, leakage and corrosion of the test equipment should be prevented.

Inflation or liquid filling: Use pressure testing equipment to slowly fill the packaging bag with gas or liquid and observe the pressure gauge.

Observation and recording: After reaching the specified pressure, maintain it for 1-5 minutes, observe whether there is any leakage, rupture, or other conditions at the heat sealed area, and record it.

Result judgment: According to the pressure values specified in relevant standards, if there is no leakage or rupture, the heat sealing strength is qualified, otherwise it is unqualified.

In addition to following the operating norms and standards of general testing methods, the heat sealing strength test of food packaging bags also needs to consider the special characteristics of food packaging, such as compatibility with food and hygiene requirements. When necessary, other testing methods or indicators should be combined to comprehensively evaluate the quality and performance of food packaging bags.