Scope:

In ASTM D570 method, the relative rate of absorption of water by plastics when immersed is determined. This test method is suitable for use with all sorts of plastics, including cast, hot-molded, and cold-molded resinous products, as well as homogeneous and laminated plastics. This rate of water absorption test method serves two purposes: first, as a guide to the proportion of water absorbed by a material, and second, as a control test on the uniformity of a product. The second function is particularly useful for sheet, rod, and tube arms when the test is performed on the finished product.

Procedure:

This method, ASTM D570, first involves the twenty-four-hour immersion in which the conditioned specimen are placed in a container filled with distilled water, and its temperature should be maintained at 23 6 1°C (73.4 6 1.8°F). After a 2-hour immersion, a specimen may be weighed to the nearest 0.001 g, then returned in the water and weighed again after 24 hours. Then specimens are placed in a container of boiling distilled water for different hours. In the end, data is compared with absorption values of other plastics.

Data:

In ASTM D570 test method, the percentage increase in weight can be calculated as follow:
Increase in weight, % = wet weight ­ conditioned weight/conditioned weight × 100
Percentage of matter lost during immersion can be calculated as follow:
Soluble matter lost= conditioned weight ­ reconditioned weight/conditioned weight × 100