COBALT-FREE HUMIDITY INDICATOR CARD BASED ON ORGANIC DYES
Journal: i TECH MAG (Technical Note)
Author: Kohei Matsumura, Yoshiaki Uryu, Takahiro Uno, Masataka Kubo
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
Since International Agency for Research on Cancer (IARC) determined that cobalt (II) chloride is carcinogenic to human, cobalt-free humidity indicators have attracted considerable attention. The composites of polystyrene sulfonic acid (PSS) with various organic dyes based on organic dyes were coated on a polyethylene terephthalate (PET) film. The coated film exhibited color change depending on humidity. The change of color was evaluated by using L*a*b* coordinates. Further, addition of hygroscopic inorganic salt such as magnesium chloride was found to be effective in tuning humidity range.