Fabrication of Eco-friendly Time Indicator Using Cellulose-Based Materials

An eco-friendly time indicator (TI) was developed using cellulose-based materials. The TI comprises a dye, copy paper, nanofibrillated cellulose (NFC) film, and filter papers coated with NFC slurry and/or paraffin-free biowax. A suitable dye and its conditions were determined by observing the dye solutions and the migration pattern at the different concentrations. Commercial filter papers were prepared, and the dye migration rate, depending on physical properties, was evaluated. NFC was coated to control the dye migration rate of filter paper. In addition, biowax was used to impart hydrophobicity to filter papers used for supporting NFC films, storing the dye, and allowing the migration of dye. Finally, a TI was fabricated using those components. Methylene blue was selected as a dye for the TI due to its deep color and high solubility. The results showed that the key property of filter paper affecting the dye migration rate was the pore size. The migration rate could be reduced when NFC was coated on both sides of the filter paper. Since biowax modified the hydrophobicity of filter paper surface, it was used to make the NFC film-supporting paper, location for dye storage, and bottom-layer. In conclusion, a multilayered TI could be assembled using cellulose-based materials.