A Heat‐Resistant Polymer Based on the Reversible Change in Polymer Skeleton Structure for Self‐Anticounterfeiting

Luo, Hong; Li, Wa; Yuan, Rui; Huang, Ying; Chen, Junze; Yang, Li; Chang, Guanjun

doi:10.1002/marc.202300516

Cited by 1 publication

(1 citation statement)

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“…Heat-resistant polymers have been studied for a long time [ 1 ] and have been widely used as various industrial products in recent years [ 2 , 3 , 4 , 5 , 6 ], e.g., heat-resistant tableware, automotive lighting components, copier gears, organic light emitting diode (OLED) displays, etc. Polyamide is a typical heat-resistant polymer; for example, nylon six has a melting point of 215 °C [ 7 ], NomexTM has a melting point of over 520 °C [ 7 ], and aramid nanofiber separators have a 5 wt% decomposition temperature of 447 °C [ 8 ].…”

Section: Introductionmentioning

confidence: 99%

Effect of Water Absorption on Electric Properties of Temperature-Resistant Polymers

Watanabe,

Kaneko,

Zhong

et al. 2024

Polymers

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The effects of water absorption on the electric resistivity and dielectric constant of polyimide (PI) and poly(ethylene terephthalate) (PET) were investigated, and the mechanism of deterioration in electrical insulation properties was discussed. The polyimides are poly(oxydianiline pyromellitimide) (PMDA–ODA) and poly(para-phenylene diamine biphenyltetracarboxydiimide) (BPDA–PDA). These polymer films were immersed in pure water for various immersion times at room temperature, and the water absorption ratio was evaluated. The electric resistance for these films was measured at room temperature using a high-resistance meter, and the dielectric constant at room temperature was measured using an LCR meter in a frequency range of 200 kHz to 2 MHz. The absorption ratios at equilibrium absorption for PMDA–ODA, BPDA–PDA, and PET were 2.7, 2.5, and 0.5%, respectively. The critical volume fraction of the percolation threshold of electric conductivity due to water absorption was 0.034 for both PMDA–ODA and BPDA–PDA. On the other hand, PET did not show a significant decrease in the resistivity. For both PIs and PET, the dielectric constant observed could be explained by a series model of the respective capacitances of pure water and polymer. Actually, the resistivity of samples cut from the edges of the film after water absorption was almost the same value as that in the dry state. These results suggest that the absorbed water molecules are not uniformly dispersed in the film but are localized at the edges of the film even after the absorption equilibrium has been reached.

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