Just looked this up.... and it mentions BFGoodrich carbopol.
Also looked up carbopol and came across this...
"Carbopol® rheology modifiers are proven exceptional thickeners, suspending agents and stabilizers" Carbopol® Polymers - Personal Care - The Lubrizol Corporation
Not sure if carbopol and carbopol rheology modifiers are the same but if it is, I am assuming this could act as a filler?
Perhaps someone with a more chemical back ground can chime in.