ASTM D570 is a test method to calculate the relative Water Absorption of plastics in 24 Hours when immersed in water under equilibrium conditions. Results help to evaluate the material performance in water or humid conditions come across during application.
The Water Absorption test by ASTM D570 is used for the calculation of the relative water absorption rate by plastics during immersion in specified conditions. This test method is intended for testing the shape of a rod, a tube, or sheets of homogeneous and laminated plastics, including cast, heat molded, and cold-molded resin materials. Factors affecting water absorption include the plastic form, additives used, temperature, and exposure length. The data helps to clarify the material performance in water or humid conditions.
The samples are dried for a given time at specified temperature and placed in a desiccator to cool for the ASTM D570 test. The samples are measured immediately after cooling. Then the material is placed inside water under specified conditions, usually at 23°C for 24 hours or until it reaches an equilibrium. Finally, the samples are removed from the water, patted dry with a lint-free cloth, and weighed.
Two-inch diameter disks, 0.125 inches or 0.250 inches thick discs are used.
Water absorption is expressed as an increase in weight percent. Percent Water Absorption = [(Wet weight – Dry weight)/ Dry weight]100