It sounds like it is not PPV as that won't cure with PMMA monomer. Sounds more like St. George Powder PMMA, it can be used with several different liquids and is still FDA but not CE when you mix. The truth is most of the materials come from DuPont and are private labeled, and maybe specialty ground. The powder, which is in many cases liquid that is UV& heat cured with the dies & fillers each mfg wants in their brand. Look at Fricke HI-I under a 30x scope and U will see a specific shape, & size mix, look at their pour and the bigger pieces have been rolled after ribbon cutting to make them flow. In Densply 199 there are 5 or more sizes which is one way to form color, but the particles with more color tend to be heavier and as they use a round particle they easily shift and settle requiring regular mixing to maintain a consistent color. Diamond D noticed the settling problem and has their color made in liquid prior to grinding & cutting to eliminate the color change from the top of the container to the bottom, but I shake it out of habit anyway. But anyway they should offer a MSDS and U can compare the CAS number if it is not on the MSDS then request it. The Vynacron in NJ is 18009327612, Bob used to send out a sample if you request.