Core & Mold Binders

OPTES supplies two main binder-related product families: sodium silicate binders manufactured at its production facility in Egypt, and green sand additives supplied through its partnership with James Durrans, UK. The sodium silicate range includes CORE BOND PRO, an aqueous sodium silicate binder, and CORE SET PRO, a liquid ester setting agent. Together, these products cover sodium silicate mold/core systems and green sand molding systems for ferrous and non-ferrous foundries.

CORE BOND PRO is an aqueous sodium silicate binder designed for foundry mold and core making. It bonds sand grains through an inorganic silicate network, producing high green strength and good thermal stability during casting. The binder is suitable for ester curing, CO₂ gassing, and thermal setting systems, allowing foundries to select the curing route according to process design and production requirements.

Sodium silicate binders are inorganic binder systems known for low odor, low gas generation, and good dimensional stability compared with many organic binder systems. They provide strong sand bonding and thermal resistance during metal pouring, making them suitable for a wide range of ferrous and non-ferrous casting applications. Their performance depends on binder dosage, sand quality, curing method, mixing efficiency, and storage conditions.

CORE BOND PRO is compatible with the three main sodium silicate hardening methods: ester curing, CO₂ gassing, and thermal setting. Ester curing provides chemical hardening through reaction with an ester setting agent, while CO₂ gassing accelerates silicate gel formation by carbonation. Thermal setting uses heat to strengthen the silicate bond and is selected where the process requires temperature-assisted curing.

CORE SET PRO is a liquid ester setting agent used for CO₂-free curing of sodium silicate-bonded sand. It reacts with sodium silicate binder to form a hardened silicate gel structure without the need for CO₂ gas equipment. This makes it suitable for foundries seeking a controlled chemical setting process, especially for mold and core applications where gassing equipment is not preferred or not available.

In ester curing, the sodium silicate binder hardens through a controlled chemical reaction between the binder and an ester setting agent. In CO₂ gassing, carbon dioxide reacts with sodium silicate to form a silica gel network that binds the sand grains together. Ester curing is often preferred for controlled setting through the full sand mass, while CO₂ gassing is commonly used for faster hardening where gas penetration and core geometry allow effective curing.

Controlled collapsibility is important because sodium silicate systems can produce strong inorganic bonds that may become difficult to break after casting if the formulation is not optimized. Good collapsibility supports easier shakeout, reduced casting cleaning effort, and lower risk of casting damage during core removal. The final collapsibility depends on binder chemistry, dosage, sand type, curing method, pouring temperature, and casting geometry.

OPTES supplies customized coal dust/bentonite blends as the main green sand additive family through its partnership with James Durrans, UK. Additional tailor-made additives may include highly volatile hydrocarbons, graphite, soda, and starch according to the foundry's sand system requirements. These products are selected to support mold strength, thermal stability, casting surface finish, and stable sand system behavior.

Coal dust/bentonite blends are green sand additives used to improve mold strength, thermal behavior, and casting surface quality. Bentonite provides clay bonding through montmorillonite, while coal dust contributes to the formation of a reducing atmosphere and lustrous carbon layer at the mold-metal interface. This helps reduce metal penetration, improve surface finish, and support more stable green sand molding performance.

Montmorillonite is the active clay mineral in bentonite responsible for swelling, water absorption, and bonding performance in green sand systems. Higher active montmorillonite content generally supports better green strength, improved mold stability, and more efficient clay usage. However, final sand performance also depends on moisture control, mixing efficiency, return sand temperature, dead clay level, and overall sand system balance.

Green sand additives improve casting surface finish by controlling the mold-metal interface during pouring. Coal dust and carbonaceous additives can generate reducing conditions and lustrous carbon, helping reduce metal penetration, burn-on, and surface roughness. Bentonite quality, sand grain distribution, moisture level, and compactability also strongly influence the final casting surface.

The selection depends on the molding process, casting geometry, alloy type, production volume, required dimensional accuracy, and shakeout requirements. Sodium silicate binders are typically used for chemically bonded cores and molds requiring controlled strength and thermal stability. Green sand additives are used in clay-bonded molding systems where sand system stability, compactability, moisture control, and surface finish are the main performance drivers.

Yes. OPTES can support customers by reviewing the sand system, alloy type, curing method, mold/core design, production cycle, and casting defects observed in operation. Binder and additive selection should be based on the actual process conditions, including sand quality, moisture level, temperature, mixing efficiency, and required shakeout behavior. This technical review helps match the correct product to the foundry's process rather than selecting only by product name.