PlatSil® 73-40 Silicone Rubber

platsil-73-40PlatSil® 73-40 is a mid-range hardness (A40) platinum silicone rubber designed for making long-lasting, flexible molds to cast liquid plastics or rubbers (polyurethanes, polyesters and epoxies) as well as polyurethane foams.

PlatSil 73-40 can also be used to cast waxes (foundry applications or candles), plasters (gypsum or fiber-reinforced gypsums), soaps, and all varieties of concrete (wet-casts, glass-fiber reinforced concrete-GFRC). Since PlatSil 73-40 has no shrinkage upon curing and resists mold distortion due to casting, it is an ideal product where dimensional stability is required.

PlatSil 73-40 is a 1A:10B mix and has a yellow-colored Part A for easily identifying when material is properly mixed. PlatSil 73-40 also has Polytek’s signature high, knotty tear strength and offers excellent chemical resistance and elongation as well. As with all Polytek silicone mold rubbers, PlatSil 73-40 allows casting to be done without release agents in most cases.

Pour as supplied or thicken for brush-on molds using PlatThix liquid thickener.


Mix Ratio Shore Hardness Pour Time Cured Color Mixed Viscosity Specific Volume Demold Time
1A:10B A40 45 min. Yellow 25,000 cP 22.0 in³/lb 16 hr.
Accessories: PlatThix Liquid ThickenerPlatSil® 71/73 Part R RetarderSilicone Fluid 50csPlatSil® 71/73 Part X Accelerator


Product Literature: Technical Bulletin | Safety Data Sheets | Physical Properties Bulletin | Sealer & Release Agent Selection Guide

Video Tutorials on YouTube: How to Make a Two-Piece PlatSil 73-40 Block Mold  |  How to Make a Mold of a Decorative Tabletop & Cast Concrete. For other video tutorials, visit the Polytek YouTube Channel.

Blog Tutorial: How to Make a One-Piece PlatSil 73-40 Block Mold


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