Q: Is there any method, equation, or software program to calculate powder density?
A: I am aware of two methods used to determine powder density. Both are covered in detail in ASTM D5965-02(2007) Standard Test Methods for Specific Gravity of Coating Powders.
One method uses the volume displacement of the powder into a fluid (kerosene or hexane) with a known density. The weight of the powder is known, so the relationship between weight and volume can then be calculated:
This method involves introducing the fluid into a graduated cylinder and recording the volume and weight of the fluid. Next, a given weight of powder is mixed into the fluid, and the displaced volume is determined. It is essential that you eliminate all air pockets in the mixture to obtain a reasonably accurate measurement.
Please be aware that this method doesn’t easily account for the surface porosity common with most powder coatings and typically results in a lower-than-true specific gravity. Nonetheless, it can be used as a decent tool to compare powders.
A much more accurate method is based on the ideal gas law and utilizes a gas pyncometer instrument, which measures volume of a known weight of powder by gas displacement. These are relatively expensive instruments and are available from a number of commercial instrument suppliers. Each instrument is slightly different; some measure volume, others can measure volume and density. You would have to consult the specific procedure provided by the instrument manufacturer to successfully measure specific gravity of powders.
I recommend you use the simpler fluid method but always run a control sample of known specific gravity along with your samples to be evaluated.