Effect of UV aging on the tensile and fracture mechanical response of syndiotactic polypropylenes of various crystallinity

Syndiotactic polypropylene (sPP) sheets of various crystallinities were subjected to accelerated ultraviolet (UV) aging. The chemical modification of the polymer was followed by FTIR spectroscopy measuring the carbonyl index in transmittance (film) and diffuse reflectance (powder) modes. Both the tensile stress and strain, suitable indicators of the UV aging, changed linearly with the carbonyl index in semilogarithmic representation. The essential work of fracture (EWF) method proved to be less suitable for characterization, as the UV irradiation resulted in surface embrittlement of the polymer. This caused brittle fracture of the notched specimens instead of the required ductile one. On the other hand, the term of the specific work of fracture related to yielding may adequately reflect the structural and morphological changes of sPP caused by UV irradiation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3462–3469, 2004