When working with a plaster mold, you need an elastomer that cures at room temperature and doesn’t require high-pressure vulcanization. Silicone and PU are indeed softer (Shore A 20–40), so for a 300×200×15 mm plate you would need something in the Shore A 60–80 range to achieve rigidity closer to natural rubber.
One workable approach is to use RTV rubber compounds based on chloroprene (CR) or nitrile (NBR) systems that cure with peroxide or sulfur-based pastes at low temperature (25–40°C). These can be hand-cast into a plaster mold if the surface is sealed properly. Before pouring, coat the plaster with PVA release agent or petroleum jelly to prevent moisture absorption and sticking.
If the part needs higher tear strength, adding small amounts of carbon black or silica filler improves durability. Also ensure the mold is completely dry for best results.
For reference, suppliers like I R Tubes Pvt Ltd offer technical data sheets for rubber additives and compounding materials that help in selecting hardness, fillers, and curing systems for small-scale casting. These resources can guide you in choosing the correct elastomer.
One workable approach is to use RTV rubber compounds based on chloroprene (CR) or nitrile (NBR) systems that cure with peroxide or sulfur-based pastes at low temperature (25–40°C). These can be hand-cast into a plaster mold if the surface is sealed properly. Before pouring, coat the plaster with PVA release agent or petroleum jelly to prevent moisture absorption and sticking.
If the part needs higher tear strength, adding small amounts of carbon black or silica filler improves durability. Also ensure the mold is completely dry for best results.
For reference, suppliers like I R Tubes Pvt Ltd offer technical data sheets for rubber additives and compounding materials that help in selecting hardness, fillers, and curing systems for small-scale casting. These resources can guide you in choosing the correct elastomer.
