Description
Poly 75-65 liquid rubber is a two-part polyurethane system from Polytek that cures at room temperature to a firm, Shore A65 rubber suited to production mold making. This 80 lb kit supplies enough Part A and Part B, mixed 1A to 1B by weight, to run multiple molds from a single batch without breaking into smaller containers mid-project.
Where Poly 75-65 Liquid Rubber Is Used
Precast concrete shops, architectural reproduction work, and sculpture and foundry studios use this rubber to build molds that hold up under repeated pours of concrete, plaster, or wax. The finished mold reproduces fine surface detail and texture, which matters for stone veneer, decorative panels, and countertop forms where the mold itself becomes part of the finished look of every casting pulled from it.
How Poly 75-65 Liquid Rubber Performs
Mixed viscosity runs about 3,000 cP with a 35 minute pour time, giving a crew enough working time to fill a detailed mold before the material starts to set. Demold time is 16 hours at standard room temperature, and the cured rubber reaches Shore A65 with 550 percent elongation and 520 psi tensile strength, properties that let a mold flex enough to release an undercut casting without tearing. Cured color is yellow, and Part B may vary in shade from batch to batch without affecting how the mold performs. Shops needing a softer, lower viscosity mix can add Poly 74/75 Part C Softener, though that extends cure time and adds some shrinkage risk across repeated castings.
Specifications
| Property | Value |
|---|---|
| Brand | Polytek |
| Product | Poly 75-65 |
| Kit Size | 80 lb kit |
| Mix Ratio by Weight | 1A to 1B |
| Shore Hardness | A65 |
| Pour Time | 35 minutes |
| Demold Time | 16 hours |
| Cured Color | Yellow |
Seal porous models such as wood, plaster, or masonry and apply a release agent before pouring, since the cured rubber bonds tightly to unsealed and unprepared surfaces. Part B contains an ingredient known to the State of California to cause cancer and genetic defects under Proposition 65, so handle it with the gloves, eye protection, and ventilation appropriate for a two-part mold rubber system. Browse mold rubber and casting materials in the molding materials category. Full technical and safety data is available direct from polytek.com.
Need Help?
Need help sizing a Poly 75-65 kit to your mold volume or picking a release agent? Call (800) 220-1966 or email [email protected].
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