Poly 74-40 Liquid Rubber

arch-restPoly 74-40 is a 2A:1B mix, A40 hardness, liquid polyurethane rubber that can be demolded in ~16 hours. It is a firmer version of Poly 74-30, our most versatile rubber.

It is often used to make molds for dimensionally stable plaster castings, poured blanket molds used for casting Glass Fiber Reinforced Cement (GFRC), and for casting plaster molds and dyes for hobby ceramic applications. Poly 74-40 molds can also be used for casting wax and limited resins (polyurethane, epoxy, polyester resin – with proper release agents).

This rubber can be poured as supplied or brushed-on by mixing in Poly Fiber II thickener or Fumed Silica.


Mix Ratio Shore Hardness Pour Time Cured Color Mixed Viscosity Specific Volume Demold Time
2A:1B A40 20 min. Varies 3,400 cP 27.5 in³/lb ~16 hr.
Accessories: 74/75 Part C Softener, 74/75 Part X Accelerator, PolyFiber II Thickening Agent, UV Additive, Tietex® Fabric, Poly Purge Aerosol Dry Gas


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

Video Tutorials: For 74-Series video tutorials, visit the 74-Series page or the Polytek YouTube Channel.


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