6 MeV pulsed electron beam induced surface and structural changes in polyimide

Abstract Thin films of polyimide (PMDA-ODA, Kapton) having 50 μm thickness were irradiated with 6 MeV pulsed electron beam. The bulk and surface properties of pristine and irradiated samples were characterized by several techniques such as stress–strain measurements, Fourier Transform Infrared (FTIR), UV–vis spectroscopy, contact angle, atomic force microscopy (AFM) and profilometry. The tensile strength, percentage elongation and strain energy show an enhancement from pristine value of 73–89 MPa, 10–22% and 4.75–14.2 MJ/m 3 respectively at the maximum fluence of 4 × 10 15  electrons/cm 2 . This signifies that polyimide being an excessively aromatic polymer is crosslinked due to high-energy electron irradiation. In surface properties, the contact angle shows a significant decrease from 59° to 32° indicating enhancement in hydrophilicity. This mainly attributes to surface roughening, which is due to the electron beam induced sputtering. The surface roughening is confirmed in AFM and profilometry measurements. The AFM images clearly show that surface roughness increases after electron irradiation. Moreover, the roughness average ( R a ) as measured from surface profilograms is found to increase from 0.06 to 0.1. The FTIR and UV–vis spectra do not show noticeable changes as regards to scissioning of bonds and the oxidation. This work leads to a definite conclusion that 6 MeV pulsed electron beam can be used to bring about desired changes in surface as well as bulk properties of polyimide, which is considered to be a high performance space quality polymer.

[1]  U. Lappan,et al.  Electron beam facility in polymer research: radiation induced functionalization of polytetrafluoroethylene , 1998 .

[2]  R. Clough.  High-energy radiation and polymers: A review of commercial processes and emerging applications , 2001 .

[3]  J. Hopewell,et al.  Effects of 3 MeV proton irradiation on the mechanical properties of polyimide films , 1996 .

[4]  S. Kucheyev,et al.  Deformation behavior of ion-irradiated polyimide , 2004 .

[5]  M. Cleland,et al.  Applications for radiation processing of materials , 2003 .

[6]  Jörg Müller,et al.  Wettability enhancement by rough surfaces generated by thin film technology , 2003 .

[7]  T. Sasuga,et al.  Degradation in tensile properties of aromatic polymers by electron beam irradiation , 1985 .

[8]  Jie Liu,et al.  The thermal-spike model description of the ion-irradiated polyimide , 2004 .

[9]  A. Chmielewski,et al.  Progress in radiation processing of polymers , 2005 .

[10]  K. K. Dwivedi,et al.  Spectroscopic and thermal studies of electron irradiated polyimide , 2003 .

[11]  C. Trautmann,et al.  Degradation of polyimide under irradiation with swift heavy ions , 2005 .

[12]  N. L. Mathakari,et al.  MeV energy electron beam induced damage in isotactic polypropylene , 2008 .

[13]  M. Kontominas,et al.  Changes in physicochemical and mechanical properties of γ-irradiated polypropylene syringes as a function of irradiation dose , 2006 .

[14]  S. Cho,et al.  Surface hardening of poly(methyl methacrylate) by electron irradiation , 2005 .

[15]  G. Wilkes,et al.  Electron beam effects on polymers. III. Mechanical and thermal properties of electron beam‐irradiated poly(phenylene sulfide) , 1989 .

[16]  J. R. Laghari,et al.  A brief survey of radiation effects on polymer dielectrics , 1990 .

[17]  V. Svorcik,et al.  Electron beam modification of polyethylene and polystyrene , 1997 .