Determination of 180° Peel Strength and Persistence of Pressure Sensitive Adhesive Tapes 2

Therefore, after grinding the test board to remove the dust as much as possible, but also with acetone or ethanol and other solvents to wipe the test, wipe the test, we must use saturated cotton dipped in solvent, the test plate tilt, gently squeeze the absorbent cotton, squeeze the solution Make sure that it flows down on the inclined test board, flush the surface of the test board, and allow the solvent to volatilize naturally, instead of rubbing the cotton ball back and forth on the test board, so as to avoid scratches caused by foreign matter on the cotton ball.
2. Test environment The temperature and humidity of the test environment also have a certain influence on the test results. Since the expansion coefficient of the adhesive layer and the adherend is different, thermal stress occurs when the temperature changes, and the internal stress and adhesive force of the adhesive system cancel each other out. If the internal stress is greater than the adhesive force, the adhesive joint is automatically released.
In the case of insufficient peristalticity of the adhesive molecules, the adhesive joints will permanently retain the internal stress and be unevenly distributed within the joints, which will cause stress concentration and affect the bonding effect.
The following is the thermal stress calculation formula caused by temperature changes:
P=ΔtΔaE/(lr)2 (2)
In the formula: Δt—temperature change value Δa—the difference between the expansion coefficient of the adhesive and the adherend.
The Young's modulus of the E-gel layer.
r - the ratio of change in horizontal and vertical dimensions.
As can be seen from the above equation, Δt increases and the thermal stress also increases. Therefore, the temperature of the test environment should be relatively stable and cannot fluctuate greatly. The test environment specified by the national standard is generally 23°C, rh: 50%.
Humidity in the test environment is also an important factor affecting the test results. If the humidity in the test environment is too high, the surface energy of the metal test plate is higher than the surface tension of the water and it will have an adsorption force on the water.
The water molecules adsorbed on the test board have penetration and expansion effects on the adhesive layer, and water molecules or water vapors rapidly diffuse in the low polarity substances, resulting in accelerated expansion of the adhesive layer, which affects the adhesive and the adhesive. Adhesive glue effect, so that the test data are affected.
The test environment should also avoid dust contamination, because when the sample is attached, dust and other debris fall on the test board or adhesive tape, the test board surface contact angle will change, so that the adhesive does not easily infiltrate the surface, affecting the bonding strength.
3. Paste operation During sample preparation, several layers of outer layer of roll adhesive tape should be stripped and the internal adhesive tape should be tested. When sampling, a special cutter should be used to adjust the required size. The longitudinal direction of the specimen should be gently rotated on the tool holder. The size of the specimen should be accurate to 1 mm or less.
Because the size of the sample increases or decreases, the accuracy of the test data will be affected. In the process of manufacturing the adhesive tape, the adhesive coating cannot be very uniform, and the interior of the adhesive is inevitably contaminated. In the bonding process, there are also May bring air, impurities, and make the adhesive surface defects.
In general, the larger the size of the sample, the greater the chance of defects, these defects will produce local stress concentration and affect the paste effect, so that the test results are affected. Therefore, the accuracy and fairness of the test can only be ensured if the specimen is made strictly and accurately to a specified size.
During the preparation of the sample, avoid touching the test site by hand. When sampling, gently pull the tape so that the substrate does not affect the quality of the plastic surface due to tensile deformation. Do not paste immediately after unwinding. Make sure that the adhesive tape is restored and attached to the test board, but do not expose the adhesive surface for a long period of time to prevent dust from falling on it.
After pasting, use the specified quality of the pressure roller, according to the standard number of times to return pressure, when rolling, just gently push the pressure roller, so that the pressure roller rolling on the sample, and can not use external pressure.
After the sample is prepared, it should be placed in a standard environment for a certain period of time to allow the substrate and adhesive surface to stabilize before testing. The length of time spent on the test data has a great influence. According to our laboratory test experience, the test that placed more than 2 hours was nearly 1 times higher than the data immediately after the sample preparation. Therefore, the test time should be determined according to the purpose of the test.
If you want to get the initial viscosity of the data, you can prepare samples for immediate testing. To assess the adhesive effect of the adhesive tape during its life, it should be tested after 20 to 40 minutes after sample preparation.
If we stick to each of the 51 sections in the paste operation, and operate it with care, we can obtain reliable inspection data. (Finish)