Ion Track Etching Revisited: IV. Thermal annealing of fresh swift heavy ion-irradiated PET in different environments

ABSTRACT

Many studies have already been performed on the thermal annealing of fresh and aged swift heavy ion-irradiated polymers in a vacuum. In this paper we examine the influence of different environments on annealing behaviour. The basic tool for this study is current/voltage spectroscopy with the alternating voltage applied across the etched tracks. In previous work of this series it was shown for etching of previously annealed aged swift heavy ion-irradiated polyethylene terephthalate foils in dry air that at ∼ 50°C, a dip overlapped the expected Arrhenius correlation in the Arrhenius plot of the etchant breakthrough times. We had attributed that dip tentatively to the etching of the swift heavy ion track core material, as the latter had been subjected to extremely high radiation-damage and thus differs strongly in its composition from pristine bulk material. Repetition of this experiment under different annealing environments enables us to draw conclusions about the competition between the different polymeric disintegration and healing mechanisms in swift heavy ion tracks. These results should be useful for better estimation of the polymeric durability in different environments. First tests with polyimide reveals that a similar dip structure also shows up here, indicating that this finding may be a general effect for annealing of ion-irradiated polymers.

KEYWORDS:

• Polyethylene terephthalate
• ion irradiation
• etching
• annealing

Acknowledgements

The project was supported by the Ministry of Education, Youth and Sports of the Czech Republic (Project 3+3, No. 05-6-1118-2014/2023, and NPI CANAM infrastructure, No. LM2015056). D.F. is grateful to the Universidad Autónoma Metropolitana-Iztapalapa, Mexico City, for the guest professorship in the frame of the Cathedra ‘Alonso Fernandez’. We are further obliged to Dr. P. Apel from JINR Dubna, Russia, for providing us with many of the examined ion-irradiated polymer foils. Part of this work was presented at the 11th International Meeting on Recent Developments in the Study of Radiation Effects in Matter in Cozumel, Q. Roo, Mexico, 12th–15th January 2020. We thank the participating colleagues for their valuable suggestions during the discussion.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 Microdeformations favour amorphous polymers as they have a relatively open structure and hence lead to easy water penetration.

2 In fact, such an annealing process, known as ‘sensitization,’ has already been used for quite a time to accelerate the sequential etching process of ion tracks in PET (26, 27). In Ref. (28) this effect was ascribed to the desorption of air components from the tracks.

3 Marker desorption tests are less recommendable if they might be influenced by polymeric phase transitions induced by eventual marker/polymer interaction (33).

4 This was done as it has turned out that usually polymer foils differ in their etchability on both sides (5). Though this side asymmetry is observed for etching of both pristine and SHI-irradiated polymers, it is more pronounced in the latter case. It was essentially attributed to the asymmetric precipitation of additives on both foil sides. During the aging process the side asymmetry increases by up to about 50%. For convenience, the foil side where etchant breakthrough is recorded first is denoted as ‘side A’; the opposite side is called ‘side B.’ All values of Figure 2 refer to results of side A. Some of the given results are averages of 2 or 3 individual measurements.

Additional information

Funding

This work was supported by Ministry of Education, Youth and Sports of the Czech Republic [grant number Project 3+3, No. 05-6-1118-2014/2023].

Notes on contributors

J. Vacik

Dr. Jiri Vacik, expert in nuclear analytical methods and materials science, group leader, Nuclear Physics Institute of the Czech Academy of Sciences, Rez, CR, E-mail: [email protected]

V. Hnatowicz

Dr. Vladimir Hnatowicz, top specialist in materials science, polymer physics and nuclear analytical methods, Nuclear Physics Institute of the Czech Academy of Sciences, Rez, CR, E-mail: [email protected]

A. Kiv

Prof. Arik Kiv, specialist in materials science, Ben-Gurion University of the Negev, Department of Materials Engineering Israel, E-mail: [email protected]

D. Fink

Prof. Dietmar Fink, top expert in materials science, polymer science, nuclear analytical methods, informally in Nuclear Physics Institute of the Czech Academy of Sciences, Rez, CR, and Universidad Autónoma Metropolitana, Mexico City, Mexico, E-mail: [email protected]