Morphological changes induced in PPS by ion bombardment: amorphisation and recrystallization ability

Abstract

Thin poly(paraphenylene sulfide) (PPS) films (Torelina, from Toray Co., Japan, 2 μm thick) were bombarded with energetic 1H+ (300 keV), 4He+ (380 keV), 10B+ (350 keV) and 40Ar2+ (700 keV) ions at fluences ranging from 1012 to 8 × 1014 ions/cm2. The beam current density was kept at 20 nA/cm2 in order to avoid excessive heating and outgassing damage. The modified samples were analysed by differential scanning calorimetry (DSC). Both the melting onset temperature and the enthalpy of fusion, that are related to the crystalline structure, decrease with increasing ion fluence. This systematic study, made with successive heating and cooling cycles in the DSC measurements, shows that the ion bombarded polymer gradually lost its crystallinity and its ability for recrystallization, as the ion fluence increases. Over a critical fluence, which depends on the bombarding ion and energy, the amorphisation process accelerates and above a certain fluence the polymer becomes completely amorphous. The above discussed modification in the PPS morphology occurs in a fluence range where the chemical degradation was not significantly noticed by Fourier transform infrared spectroscopy (FTIR) measurements. The modification radii for the amorphisation process were extracted and the results discussed considering the energy deposition density.