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Polyurethane liquid casting rubber Shore A 30 (Poly 74-30)

The Poly 74-30 is a two-component liquid polyurethane casting rubber. This RTV rubber has an amber color during hardening and a hardness Shore A 30. By adding an additive CAB-O-SIL or PolyFiber, the liquid rubber can also be used as brushable rubbers. The rubber can then be used layer by layer as a layer-up technique for molds such as walls or ceiling. The Poly 74 series is often used for making molds and rubber products such as molds for objects with undercuts, restoration, concrete casting, various art products, architectural reproduction, various crafts, displays and industrial applications. The Poly 74-30 is a soft Shore A 30 rubber with a 30 min. Processing time and a 24 hour curing time.

The Poly 74-30 polyurethane rubber is an RTV (Room Temperature Vulcanization) pour rubber. The Poly 74 and 75 series products are very strong and durable so perfect for making durable molds. The Poly 74 and 75 series have been specially developed for making molds for the production and casting of concrete molds. The Poly 74-Series is a soft rubber for producing molds and products for the Prefab. The Poly 74 and Poly 75 Series are known for reproducing fine details and texture.

The Poly 74-30 is available in sets of 2 kg, 10 kg, 36 kg and 408 kg.

Packaging: Set 408 kg (204A+204B), Set 2 kg, Set 10 kg, Set 36 kg
Hardness (Shore A): 30
Mix Ratio: 1A:1B (by weight)
Working Time (min): 25-30
Total Cure (hr): 16 hr (demold) / 7 days (100%)
Color: Amber
Viscosity (cP): 2.000
Tear Strength (N/mm2): 10.86
Tensile Strength (N/mm2): 1.94
Type product: Polyurethane rubber


Description of the Poly 74-Series polyurethane rubbers

Poly 74-Series Polyurethane Rubbers consist of two components (A and B), which after mixing both parts at room temperature (RTV) harden into flexible, very strong, polyurethane molded rubbers. Poly 74-Series Rubbers are durable, easy-to-release rubbers for making molds for casting plaster products, wax and resin materials such as various polyurethane and epoxy materials. Some wax and plaster products can even dissolve without a release agent. The Poly 74 series is also very well suited for making concrete moulds. The Poly 74 series are soft polyurethane rubber for making rubber parts from Shore A 20 – Shore A 50. For a better lifespan and better release, we recommend using a release agent.


Good preparation helps to achieve the desired quality and often ensures trouble-free casting. Preparation includes preparing both components, mixing tools, scales or measuring cups, controlling the temperature, and ensuring that pouring can be done immediately. But also use the right method, release agents and sealers,

Porous models, such as wood, plaster, stone, pottery or masonry must be sealed with a sealer, because these pores suck the rubber full. We have a special pore sealer that can close these pores with a very thin film layer. Otherwise, you can also use several layers of dried wax paste that must be polished afterwards. This will seal most surfaces. Pottery soap can be used as a sealer for plaster. Lacquer, paint, PVA and Pol-Ease® 2350 Release Agent also work well as sealers for many surfaces. The properly sealed model should then be coated with a release agent (eg Pol-Ease® 2300 Release or release agent VL). Alternatively, PolyCoat, a sealer and semi-permanent release agent, can be used on most porous or non-porous models. Porous models must be ventilated from below to prevent air from forming bubbles in the rubber. To do this, make a hole in the bottom plate so that these models can breathe in it. Models made of sulfur-containing modeling clay (eg Roma Plastilina) must be sealed with shellac. (NOTE: When using shellac as: the sealer, it must be coated thoroughly with a release agent because: polyurethane rubbers adhere strongly to shellac.) Non-porous models (e.g. metals, plasticine, wax, glazed ceramic, fiberglass and polyurethane ) should be coated with a release agent such as Pol-Ease® 2300 release agent, Release Agent VL or PolyCoat. Also take into account wet products such as natural clay, which can react with the rubber. Polyurethane rubber cannot withstand moisture and water. We always recommend doing a test before you start your project! This way you know more about possible adhesion and release and compatibility between the materials.

Mixing and Curing:

Ensure parts A and B are at room temperature before use, the casting chamber is at room temperature and all tools are ready. Surface and air temperatures must be above 15c/ 60°F during application and throughout the curing period;
period of time. We advise to keep room temperature of 25°C and this is what our processing times and curing times are based on. The lower the temperature, the thicker the material and the longer the processing and curing takes, the higher the temperature, the faster the curing and processing and the lower the viscosity.

Check the mixing ratio before you start. Several Poly 74-Series Part Bs must be stirred before use (i.e. 74-20, 74-29, 74-30, and 74-40). Weigh Part B into a clean metal or plastic mixing cup, then weigh the appropriate amount of Part A into the same container. Mix thoroughly. Mixing manually with a Poly Paddle is best to avoid mixing air into the rubber. Scrape the sides and bottom several times while mixing to ensure thorough mixing. Pour the rubber as soon as possible after mixing for best flow and air bubble release from the rubber. Vacuum degassing helps to obtain bubble-free molds, but is
usually not necessary. Allow the rubber to cure at room temperature, 25°C / 77°F). Carefully remove the mold or cast product from the mould/mould after approximately 16 hours.

Final curing properties are obtained in: approximately seven days, but molds can be used with care after 24-48 hours curing. Heat accelerates curing — low temperatures slow curing. Avoid curing in areas where the temperature is below 15°C. Both parts A and B react with humidity and therefore must be resealed as soon as possible after opening with e.g. Poly purge or used up. Poly Purge is a drying gas and heavier than air. This poly purge displaces moist air in the flex or bucket and can extend the shelf life. comp. A hardens through air in opened packs. For 204 kg / 55-gallon drums of parts A and B, we apply the Drierite® cartridges during dispensing to protect the product from the drums from moist air entering the drum. This dry air extends the life of the PU.

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