2.2.11. Stability Test

NDPT stability was tested under three conditions. The first treatment was drying in a controllable incubator Eyela (Tokyo, Japan), which was set at 30 ± 0.5% RH/40 ± 0.5 ◦C to observe water release. Sample was taken from the incubator after 0, 2, 4, 6, 12, and 24 h of drying. The second treatment consisted of the NDPT sample at room humidity and temperature (72 ± 2% RH/25 ± 2 ◦C), which was sampled periodically until 72 h. The third stability test was performed by storing the dried sample at high relative humidity (~94% RH), which was prepared by filling a chamber with a saturated solution of potassium nitrate [16]. Sampling was carried out periodically to investigate the changes of water molecules and hydrate stability for 15 days by DTA/TG, DSC, and PXRD.
