The hot-tack tensile tester is suitable for flexible thermoplastics and their composite materials, and the hot-tack performance test under different heat-sealing conditions within a specific time interval from the end of heat-sealing to the heat-sealed part before cooling to ambient temperature.
It can simulate the heat sealing conditions of different packaging production lines in the existing market, and provide direct and effective data support for customers to choose packaging materials and improve packaging filling efficiency.
The test method is based on “GB/T 34445-2017 Determination of Thermal Adhesive Properties of Hot Covers of Thermoplastics and Their Composite Materials”
Heat sealing time
The duration during which the heat-sealing knife contacts the sample and applies heat-sealing pressure during the heat-sealing process.
Delay
The time interval between the time point when the heat-sealing knife is separated and the time point when the sample is ready to withdraw after the heat-sealing process is completed.
Retracement Time
The time interval from the time point when the sample is just withdrawn to the time point when the sample is just stretched until the slack completely disappears after entering the hot tack test state.
Hot Tack Strength
The hot tack measured on the unit width of the sample during the specified time interval from the end of heat sealing to the time when the heat-sealed part has not cooled to ambient temperature.
Test Principle
Under certain heat-sealing time and heat-sealing pressure, set different heat-sealing temperatures. At a fixed heat-sealing temperature, use a heat-sealing knife to heat-seal two samples to be heat-sealed. The samples to be heat-sealed can be films of the same material or different materials. Some hot tack testers can heat seal a strip and cut the strip during the sealing process to form two specimens. The two heat-sealing knives can be heated at the same time or separately. The heat-sealing knives should be kept smooth to ensure that the heat-sealed part of the sample is evenly stressed, and can be wrapped with some material to facilitate its separation from the heat-sealing material.
Method A (the delay time is fixed and not adjustable), after the heat sealing knife is separated, and the fixed delay time and the retraction phase are over, start to draw the curve of the thermal viscosity value and time in real time, which is the cooling curve of the cooling sample. The hot tack tester determines the average hot tack force at different time points according to the drawn cooling curve, and records the corresponding hot tack force at the selected cooling time point.
Method B (the delay time is adjustable), when the set delay time is reached, the curve of the thermal viscosity value and time is drawn in real time, and the maximum force value in the process of fixture separation determined according to the drawn curve is the delay time The thermal viscosity below.
The test apparatus shall be divided into the following parts
Heat-sealing knives: 2 heat-sealing knives should be configured for heat-sealing samples.
Control device:
heat-sealing time, heat-sealing temperature, heat-sealing pressure and delay time should be selectively set and precisely controlled. The temperature control accuracy should not exceed ±0.5°C, and the pressure sensor accuracy should not exceed ±5% of the indication value accuracy .
Fixture separation speed selection device:
it should have multiple fixture separation speeds, at least 25mm/s (1500mm/min), 200mm/s (12000mm/min) The two fixture separation speeds should ensure that the speed is stable during operation, as used The hot tack tester can meet both method A and method B, and at least meet the three fixtures of 25.0mm/s (1500mm/min), 33.3mm/s (1998mm/min), and 200mm/s (12000mm/min) Separation speed.
Sample withdrawal device:
After the heat-sealing process is over, the device can automatically remove the sample from the heat-sealing knife within 0.1s and adjust it to the initial test state of the heat-adhesive test peeling process.
Force measuring device:
Measure the force value that causes the specimen to break.
Experimental procedure
Set the heat sealing temperature
The heat sealing temperature of the two heat sealing knives should be the same, and the temperature value should be selected according to the nature of the material. When drawing the hot-tack curve, you can choose a lower heat-sealing temperature, and then the heat-sealing temperature increases at intervals of 5°C to 10°C. If you want to obtain the maximum hot-tack strength or other parameters, you can appropriately reduce the temperature interval. The first temperature point on the curve is usually the onset hot tack temperature.
Set the heat sealing time
The heat sealing time should be set long enough to allow the temperature of the heat cover to reach the known temperature of the heat sealing knife, and the time depends on the thickness and structure of the specimen.
Set heat sealing pressure
The heat sealing pressure range is 0.15MPa~0.30MPa.
Clamping the sample
According to the instructions for use of the hot tack tester, the hot surface of the sample is facing and clamped on the fixture of the instrument, and the sample should be placed in alignment.
Set test parameters
The test parameters should be entered in the hot tack tester to measure the hot tack.
Start the test
Start the hot tack tester, complete the heat sealing, delay, retraction, hot tack test process in turn, and automatically record the experimental data.
Test results
The test results are expressed as the arithmetic mean value of 5 or more samples. The deviation between the test value of each sample and the arithmetic mean shall not exceed ±10%. When the test result is greater than or equal to 1N, keep 3 significant figures, and when the test result is less than 1N, keep 2 significant figures.