Views: 4 Author: Site Editor Publish Time: 2022-02-02 Origin: Site
Washi tape adhesives can be tested for creep through tensile, elongation, shearing and cutting, but what factors generally affect the creep performance?
The creep of the washi tape is generally a fixed external force, that is, the relative deformation of the sample when the tensile force, shear force and compression force change at any time. This is different from stress relaxation, which is generally a combination of relaxation and viscous flow phenomena. The influencing factors are generally polymer structure temperature, stress, fillers and plasticizers.
1. The structure of the local polymer: any factor that can increase the interaction force and thus increase the length of the chain segment, such as the increase in molecular weight, the increase in side chains or groups, the increase in the polarity of the molecule, and the degree of cross-linking. Increase, crystallization, etc., will reduce the stress relaxation of creep.
2. External factors: The creep properties of washi tape are generally strongly dependent on temperature, especially in the glass transition region. Many polymers have a maximum value of creep rate near the glass transition point (Tg). At sufficiently below Tg, only minimal creep occurs, even for a long time, and at temperatures sufficiently high above Tg, the creep rate generally decreases.
Crystalline polymers behave more complexly. Not only are their creep properties highly temperature-dependent, crystalline polymers can sometimes creep more rapidly than amorphous hard and cross-linked polymers at a given temperature.
In conclusion, an increase in temperature will not only increase the creep rate of the paper tape, but also increase the amount of creep, so it may change the creep type from a stop type to a steady state type, or even an increase type.
For amorphous polymers, creep obeys the time-temperature equivalence (superposition) principle, and WLF can generally be applied to process stress/time data over a wide temperature range, which will make the regularity of the results clearer.
The stress effect is similar to the temperature effect. The increase of stress generally increases the creep, and the addition of fillers can reduce the creep value of the washi tape. Whether it is a polymer or a low molecular plasticizer, the force between the polymer molecules can be weakened, so this is beneficial to creep, because the dispersion of the creep test results is large, and only a sufficient number of samples are tested. , you can get the correct result.