Test Principle and Equipment
The tensile testing machine records the change in force value during the peeling process by fixing the tape on a standard test plate and peeling it off at a constant rate in the 180-degree peel strength test of packaging tape. The core principle is to peel the tape sample from the stainless steel or plastic substrate at an angle of 180° according to ASTM D3330 and GB/T 2792 standards, and calculate the average force required per unit width (unit: N/10mm or N/25mm). The equipment is usually driven by a servo motor, equipped with a high-precision sensor, the loading rate can be set to 300 mm/min, and the force-displacement curve is automatically collected.
Test procedure specifications
Sample preparation was prepared at a constant temperature of 23±2°C and a relative humidity of 50±5% for 24 hours. The specific steps are as follows:
Step 1: Cut the tape sample with a width of 25 mm or 10 mm and a length of about 300 mm.
Step 2: Bubble-free bonding of the sample onto a cleaned standard test plate (e.g., 304 stainless steel plate with a surface roughness of Ra≤0.4 μm) and rolling back and forth twice at a speed of about 300 mm/min using a 2 kg roller.
Step 3: Fix the test plate on the lower fixture of the testing machine, and clamp the free end of the tape vertically upwards on the upper fixture, and adjust the peeling angle to maintain 180°.
Step 4: Start the tensile testing machine, peel at a rate of 300 mm/min, record the force value of at least 150 mm peeling section, and take the average value of the next 100 mm section.
Key parameters are compared
The following table summarizes common criteria and parameter settings:
| Parameters/indicators | Typical setting or requirement |
|---|---|
| Test Standards | GB/T 2792-2014、ASTM D3330/D3330M-04 |
| Experimental environment | 23±2°C，RH 50±5% |
| Stripping rate | 300 mm/min or 5 mm/s |
| Specimen width | 25 mm or 10 mm |
| Test plate material | Stainless steel, aluminum plate or glass plate |
| Roller quality | 2 kg, diameter approx. 50 mm |
| Peel angle | 180° |
| Data selection | At least the 150 mm middle and rear 100 mm segments are taken |
| Result unit | N/10mm or N/25mm |
Data processing and formulas
Peel strength is calculated based on the following formula:
σ = F / w
Among them, σ is the peel strength of 180° (N/mm), F is the average peel force (N), and w is the width of the specimen (mm). In practical applications, the commonly used unit is N/10mm, that is, σ10 = (F / w) × 10。 For example, if a tape with a width of 25 mm measures an average force of 12 N, then σ = 12 / 25 = 0.48 N/mm, which translates to 4.8 N/10mm.
During the test, the force-displacement curve fluctuates in a zigzag manner, and F should be calculated based on the arithmetic average of the last 100 mm peeling section. If there are obvious peaks or troughs in the curve, the maximum and minimum values should be indicated, but the standard requires that the average value shall prevail.
Influencing factor control
To ensure data repeatability, the following factors need to be controlled:
1. Test the surface cleanliness of the plate: Wipe it three times with isopropyl alcohol or acetone to dry naturally and avoid sweat contamination by hands.
2. Rolling speed and pressure: Roll twice at a constant speed to avoid bubbles or wrinkles.
3. Environmental conditions: temperature and humidity directly affect the viscoelastic properties of adhesives, and strict constant temperature and humidity are required.
4. Rigidity of the testing machine: It is recommended to choose a model with a measuring range of less than 500 N, and the deviation of the fixture is less than 0.5 mm.
FAQs & Calibrations
If the peeling curve is abnormal (such as sudden jumping of the force value), check whether the tape is in contact with the edge of the test plate, whether the test plate is deformed or the fixture is loose. The tensile testing machine is calibrated regularly using standard weights or force sensors, and it is recommended to use it once a quarter, and the offset exceeds ±1% and needs to be repaired and debugged.
Application example description
Taking BOPP packaging tape as an example (thickness 0.05 mm and width 25 mm), the average peeling force was 8.9 N and the calculated strength was 3.56 N/10mm under the condition of 23°C and RH 50%. If a higher viscosity PVC tape is used, it can reach 6.2 N/10 mm under the same conditions. Different substrates (such as carton board, polyethylene film) need to be replaced with a test plate material and recalculated.
Citation segments:
1. The 180° peel test part of GB/T 2792-2014 "Test method for peel strength of adhesive tape".
2. ASTM D3330/D3330M-04 Standard Test Method for Peel Adhesion of Pressure-Sensitive Tape。
3. A series of technical standards for "Test Methods for Adhesive Tapes for Packaging", involving the chapter on environmental regulation and data processing.