Density/Specific Gravity ASTM D792

Understanding Density and Specific Gravity ASTM D792, ISO 1183

Density and specific gravity are important physical properties of materials that can be measured using ASTM D792 and ISO 1183 standards. Density is the mass of a material per unit volume, while specific gravity is the ratio of the mass of a given volume of a material at 23°C to the mass of the same volume of deionized water. These values are particularly relevant for plastics, as lower density or specific gravity can mean more material per pound or varied part weight, which can affect the cost of production.

There are two basic test procedures for measuring density and specific gravity: Method A and Method B. Method A is more commonly used and can be used with sheet, rod, tube, and molded articles. For this method, the specimen is weighed in air and then weighed when completely submerged in distilled water at 23°C using a sinker and wire if required. Density and specific gravity are then calculated using the obtained data.

The specimen size used in the test can be any convenient size. The data obtained from the test can be used to calculate specific gravity and density. The specific gravity is calculated using the formula: specific gravity = a/[(a + w)-b], where a is the mass of the specimen in air, b is the mass of the specimen and sinker (if used) in water, and w is the mass of the totally immersed sinker and partially immersed wire, if used. The density, in kg/m3, is then calculated by multiplying the specific gravity by 997.6.

In summary, ASTM D792 and ISO 1183 standards are used to measure the density and specific gravity of materials. The test procedures involve weighing the specimen in air and when completely submerged in distilled water at 23°C using a sinker and wire if required. The obtained data is then used to calculate specific gravity and density, which can provide valuable information for manufacturers, especially for plastics, where lower density or specific gravity can affect cost and part weight.