Method for determining frequency dependent thermomechanical behavior of polymer films at cryogenic temperatures
| Autor: | Bo Bonning, Wayne R. Johnson, Holly A. Stretz, Christopher D. Wilson |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
010302 applied physics
chemistry.chemical_classification Arrhenius equation Materials science Vespel General Physics and Astronomy Modulus Activation energy Polymer 01 natural sciences Amorphous solid symbols.namesake chemistry 0103 physical sciences Dynamic modulus symbols General Materials Science Composite material 010306 general physics Polyimide |
| Zdroj: | Cryogenics. 114:103236 |
| ISSN: | 0011-2275 |
| Popis: | The purpose of this study was to investigate a parameterized mathematical approach for estimating the complex modulus of a polyimide film at extreme cryogenic temperatures (e.g. 4 K). Such films are used in extreme cryogenic applications such as superconducting magnets and electronic devices. A polymer core of the electronic laminate, Pyralux AP8525R (polyimide), was tested on a TA Instruments Q800 dynamic mechanical analyzer from 140 K to 293 K to obtain complex tensile moduli, and these data were then extrapolated using multiple types of fits. For one predictive method, activation energy of flows, Ea, were calculated using an Arrhenius model and frequency-temperature superposition. All fits were projected to 4 K. A second type of fit was a T3 model. A validation study using Vespel, a material where dynamic modulus had been previously reported at 4 K, was also performed. The validation study indicated that for similar materials (e.g. amorphous aromatic polyimides) a cubic parametrized fit might be the most useful predictive tool. Other polymers reported as tested to 4 K in the literature exhibited a plateau in modulus at low temperatures (sigmoidal fit). From the literature, an amorphous aromatic polyimide and polystyrene showed an increase in modulus at low temperature which is inconsistent with a plateau or sigmoidal fit. The T3, or cubic model, was chosen as the best predictive method for the modulus of the Pyralux core polymer. The theoretical rationale for a cubic fit is discussed, though why (of the three proposed methods) only two polymers to date are reported to exhibit this behavior near 4 K remains unclear. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect