Ultra-Pflex PCC Precipitated calcium carbonate Specialty Minerals Rheology Modifiers / Thickeners >> Mineral >> Precipitated calcium cabonate Epoxy (EP) Polysulfides PU - Prepolymers Polyvinyl Chloride (PVC) SEALANT The only domestically produced ultrafine coated 0.07 micron PCC product. ULTRA-PFLEX® PCC is used extensively in automotive and construction sealant systems including PVC, plastisols, polysulfides, urethanes and epoxies as a rheological additive to provide excellent sag and slump resistance. Ultrafine coated precipitated calcium carbonate. Used as rheology modifier in sealants. Provides very good sag and slump resistance.