Abstract
The effects of UV fluence on strength properties of PEEK films were investigated based on tensile tests. Elongation at break clearly decreased with increasing UV fluence although yield strength and elastic modulus were almost same before and after irradiation. Surface observations during tensile tests and fracture surface observations clarified that small cracks with a depth of a few ttm initiated at irradiated surface, and that true stress at which crack initiated decreased with increasing UV fluence. The analyses of chemical structure at UV irradiated surface by using FT-IR method confirmed the increase of carbonyl bonding at the depth corresponding to the small cracks, which caused the embrittlement of the surface layer. Small cracks initiated at the thin embrittled layer propagated and coalesced each other during tensile tests. This phenomenon can be the main reason for the decrease of elongation at break of UV irradiated PEEK films.
