Available online at www.sciencedirect.com Radiation Measurements 36 (2003) 621 – 624 www.elsevier.com/locate/radmeas Spectroscopic and thermal studies of electron irradiated polyimide R. Mishra a; c ; ∗ , S.P. Tripathy a; c , K.K. Dwivedi b; d , D.T. Khathing c , S. Ghosh d ,M.M uller d , D. Fink d a Italian National Agency for Environmental Protection, ANPA, Via. V. Brancati 48, 00144 Rome, Italy b Arunachal University, Rono Hills, Itanagar 791 111, India c Department of Physics, North-Eastern Hill University, Shillong 793 022, India d Hahn Meitner Institute, Glienicker Strasse, 100, D-14109 Berlin, Germany Received 21 October 2002; received in revised form 20 February 2003; accepted 7 May 2003 Abstract The present work looks into the modication in spectroscopic and thermal behaviour of polyimide (PI), induced by 23 kGy dose of 2 MeV electron. The pristine and the irradiated polymers were characterised by Fourier transform IR spectroscopy (FT-IR), thermogravimetric analysis (TGA) and dierential scanning calorimetry (DSC). Though emergence of any new structures after irradiation was not observed, yet a decrease in thermal stability of the polymer accompanied by decrease in the melting temperature was observed after irradiation. c  2003 Elsevier Ltd. All rights reserved. Keywords: Polyimide; Electron irradiation; Thermal stability; Absorbance; Melting temperature 1. Introduction Thermally stable organic polymers have been the sub- ject of numerous studies in order to extend the application of organic materials in harsh conditions. Of thermally stable organic polymers, the outstanding properties of aro- matic polyimides (called later on PI) such as excellent thermo-oxidative stability and superior chemical resistance led to the use of polyimides in many applications, such as insulating materials for electronics, semi-permeable membranes for gas separation, and high temperature adhe- sives and coatings (Chung and Kim, 1998). PI contains a charge transfer complex consisting of two dierent types of monomers, a donor and an acceptor. The donor has a plenty of electrons to go around because of its nitro- gen groups. The acceptor has carbonyl groups that sucks ∗ Corresponding author. Italian National Agency for Environ- mental Protection, ANPA, Via. V. Brancati 48, 00144 Rome, Italy Tel./fax: +39-6-5007-2941. E-mail address: mishra@anpa.it (R. Mishra). away the electron density. So, this results in a strong inter- molecular forces in the polymer structure. Moreover, pres- ence of imide and aromatic rings in the structure of polymer is at the origin of improved heat resistance and stability to ionising radiation. Ion beam irradiation studies in PI showed a dramatic modication of the diusion, which result from creation of static free volume (Davenas et al., 1997). Main chain scission leading to degradation of the polymer has been evidenced in PI by krypton and molybdenum ion ir- radiation, along with the formation of triple bond species such as alkynes and cyanates (Steckenreiter et al., 1999). Random co-polymerisation reduces the chain regularity, re- sulting in improved solubility of rigid polyimides (Chung et al., 2001). 2 MeV electrons were found to improve the track registration properties of PI (Mishra et al., 2001). Degrada- tion and oxidation of aromatic polyurethane was observed as a function of depth and dose of 200 keV electron beam (Ravat et al., 2000). In the present case, the eect of 23 kGy dose of 2 MeV electron on the polymer PI was studied by dierent characterisation techniques viz. FT-IR, TGA and DSC. 1350-4487/03/$ - see front matter c  2003 Elsevier Ltd. All rights reserved. doi:10.1016/S1350-4487(03)00212-9