Depth profiles of high-density polyethylenes filled with different inorganic fillers during natural photo-oxidation by infrared microscopy

The natural photo-oxidation degradation of HDPE filled with different inorganic fillers was carried out, and the depth profiles of the standard samples were characterized by infrared microscopy (IM) and scanning electron spectroscopy (SEM). The results show that HDPE filled with different inorganic fillers show different depth profiles. For HDPE and CaCO3-filled HDPE, there are no cracks on the cross sections, and the carbonyl indexes remain nearly zero from the surface to the interior. For HDPE filled with black mica, mica, kaolin and diatomite, there are more or less parallel, comb-like cracks on the cross sections, and the carbonyl indexes show decreasing trends from the surface to the interior. Furthermore, the transition points in CI curves are basically consistent with the formation of cracks in these samples. The UV absorbances of these inorganic fillers demonstrate the relationship between the photo-oxidation of HDPE and the relative absorbances of inorganic fillers. This implies that the UV absorbance of the inorganic filler may be responsible for the occurrence of cracks and oxidation in the standard samples.