On the Creep Behavior of Adhesive in High Temperature Tape!
High temperature adhesive tape can be tested for creep by pulling, stretching, cutting, and shearing, but what factors affect creep performance?
Creep of high temperature adhesive tape is the relative deformation of the specimen over time when a constant external force (tensile force, shear force, compression force) is applied. Unlike stress relaxation, creep is generally a combination of relaxation and viscous flow phenomena. Its influencing factors are mainly polymer structure and temperature, stress, filler, plasticizer, etc.
1. Structure of high temperature adhesive tape polymer
Factors that can increase the interaction force between large molecules or increase the length of chain segments (motion units), such as increasing molecular weight, increasing side chains or groups, increasing polarity, increasing crosslinking degree, crystallization, etc., all reduce creep and stress relaxation.
2. External factors of high temperature adhesive tape adhesive
The creep properties of high temperature adhesive tape strongly depend on temperature, especially in the glass transition region. Many polymers have a maximum creep rate near the glass transition temperature (Tg). At temperatures low enough below Tg, even for a very long time, only a very small creep occurs. At temperatures high enough above Tg, significant elongation occurs, but the creep rate generally decreases.
The behavior of crystalline polymers is even more complex. The temperature dependence of their creep properties is not only strong, but also in some cases, crystalline polymers show more creep over time than amorphous hard polymers and crosslinked polymers at a given temperature.
In summary, increasing temperature not only increases the creep rate of high temperature adhesive tape, but also the creep amount. It may also change the creep type from stop type to stable type, or even growth type.
For amorphous polymers, their creep follows the time-temperature equivalence (superposition) principle. WLF can be used to process stress/time data over a wide temperature range to make the regularity of the results clearer.
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