On the nature of segmental mobility of dense-network epoxy polymers

Tarasov, V. P.; Smirnov, Yu. M.; Yerofeyev, L.N.; Иржак, В. И.; Розенберг, Б. А.

doi:10.1016/0032-3950(83)90457-4

Cited by 5 publications

(1 citation statement)

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“…30 °C for CL-3, 50 °C for CL-4, and 56 °C for CL-6. The result indicated that T g increased with increasing f, thereby revealing that the segmental mobilities of the samples with larger f were more restricted than those of the samples with lower f. 49,50 TGA results shown that the thermal decomposition temperature, i.e., 5% weight loss temperature, was much higher than 250 °C (Figure S7), and the difference between the samples was negligible.…”

Section: ■ Resultsmentioning

confidence: 99%

Critical Effects of Branch Numbers at the Cross-Link Point on the Relaxation Behaviors of Transesterification Vitrimers

Isogai

Hayashi

2022

Macromolecules

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Vitrimers are functional cross-linked materials, exhibiting reprocessability, recyclability, and healability, and thus these are expected for application as sustainable materials. The functionalities of vitrimers are attributable to their associative bond exchange mechanism that is activated at a certain high temperature. The construction of a tuning method for the bond exchange properties must be useful for coming practical application of the vitrimer concept. Here, we prepare transesterification-based vitrimers via the thiol−epoxy click reaction to elucidate the essential effects of the branch numbers (f) at the cross-link point on their bond exchange properties, where f can be readily tuned via the functionality of the starting materials. The temperature-ramp creep and stress−relaxation tests then demonstrate that the vitrimer properties, such as the softening and stress−relaxation behaviors, vary depending on f. The experimental results derive some empirical relationships between f and the relaxation time and between f and activation energy of the bond exchange. In addition, the relaxation behavior of the vitrimer network with mixed f is investigated in the final section, showing the relaxation rate can be determined by the harmonic mean of relaxation time weighted by the mole fraction of the network components having different f. Overall, this study demonstrates that the design of a proper f is crucial to obtain the desired properties of vitrimers.

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Section: ■ Resultsmentioning

confidence: 99%