Staining of water trees with methylene blue explained

摘要

Staining with a methylene blue solution, a popular technique for achieving the required high contrast images of water trees, was carried out at 70 degrees C. It is shown that methylene blue stains the complete tree, which justifies water tree length measurements after staining. The water tree is not stained exclusively, but rather faster and probably to a higher degree than the polyethylene. Comparing optical microscopy images of water trees before and after staining, it was found that the entire tree becomes visible. Comparison of FTIR (Fourier-transform infrared) spectra measured before and after staining did not indicate that a chemical reaction is required in the staining process. In general, the staining of water trees with methylene blue can be explained by mere diffusion. The enhanced temperature of 70 degrees C helps to increase the permeability of the polyethylene.