PPG-6, PPG-8, PPG-12, PPG-40, PPG-150, etc.
Polypropylene glycol is a family of long chain polymers attached
to a glycerine backbone.
Like the closely related compound
PPG is used as a thickener in many products. It is used in toothpaste
to prevent bacteria from breaking down the pyrophosphates used to
control tartar buildup.