Calcium Oxide (CaO) for Defoaming Masterbatch


Calcium oxide, molecular formula CaO, is a good material for absorbing moisture, defoaming, and drying for chemical materials like plastics, rubber, etc.

Calcium oxide is usually achieved by heating a material containing calcium carbonate such as limestone above 825°C to get quicklime and release carbon dioxide (CO2).

CaCO3(s) → CaO(s) + CO2(g)

Calcium oxide exposed to air absorbs carbon dioxide and gradually becomes calcium carbonate.

CaO is easily soluble in acid and difficult to dissolve in water but can become calcium hydroxide with water.

Technical Index

CaO Content %≥


Particle Size (Mesh)



Moisture absorption, defoaming, drying

Calcium Oxide

Physical & Chemical Features


Calcium Oxide




Quicklime, burnt lime, pebble lime

Chemical Formula


Molecular Weight (g/mol)



White to light grey powder




Soluble in water (generate heat), glycerol;

Insoluble in methanol, ethyl ether, octanol

Density ( g/cm3)


Boiling Point (°C)


Melting Point (°C)


CaO for Defoaming Masterbatch


There is a common problem in plastics manufacturing. In the twin-screw extruder, the moisture contained in the plastic itself rapidly vaporizes when the plastic is heated above 100°C. As the moisture is wrapped by the molten plastic, it cannot get into the air but remains inside or on the surface of the plastic, forming many bubbles.

Such bubbles will affect the appearance of plastic products, and can lead to a significant decline in its mechanical properties.

The traditional process of using electric drying machinery to eliminate moisture requires advanced drying of raw materials. This not only causes inconvenience to production, but also low productivity, power consumption, environmental deterioration and increase in cost due to longer processing time.

Plastic defoaming masterbatch, whose main components are carrier, calcium oxide, and dispersant, is a functional filler specially developed to solve the bubble problem in the processing of plastics.

Plastic defoaming masterbatch is non-toxic and non-polluting, and do not affect the properties of plastic products. Its good water absorption can improve product quality and yield, significantly improve productivity and reduce energy consumption.

Plastic Defoaming Masterbatch


Calcium oxide can also be added to rubber as a drying agent/defoamer.

Rubber products are continuously vulcanized at high temperatures and regular atmospheric pressure. Due to the moisture effect in the compounding agent, there are always bubbles in rubber products. In order to avoid bubbles during vulcanization, the compounding agent needs to be thoroughly dried before mixing.

It is also necessary to add drying agent in the rubber material, whose main component is calcium oxide of fine particle size (320 mesh or more). In the compounding and vulcanization process, calcium oxide is combined with moisture to generate calcium hydroxide. Therefore, it can avoid bubbles in rubber products.

Other Uses

In metallurgical co-solvent, chemical raw materials, architectural coatings, paper making, wastewater purification, filler tanning, waste incineration, acid and alkali neutralization in metal factory, bleaching, desulfurization and acid removal in thermal power plant, petroleum lubricating oil, feed, stone cutting aid, inlay coagulant for gypsum board, astringent, etc.

Package & Cautions

25kg/bag. Woven bag lined with double-layer inner film bag or paper-plastic composite bag.

This product is an inorganic alkaline corrosive powder. It is irritating to the respiratory and digestive tracts, eyes, and skin, and can cause burns. The operator should be well protected. If the powder come into the eyes or on skin, immediately rinse with flowing water.

The powder should be stored in sealed packages in a cool, dry, and ventilated warehouse from moisture, rain, or sunlight. Do not mix it with acids for storage or transportation. In case of fire, use dry powder, carbon dioxide or dry sand to extinguish the fire.

Why Hoyonn

Hoyonn Chemical has been in the polymer industry since 2001. We specialize in mineral development, powder processing, R&D innovation, and global sales of barium sulphate and various functional fillers and additives. We have our plants and know-how to supply worldwide customers from powder coatings, paints, plastics, rubber, ink, and more industries.

  • 20 years of expertise in the polymer industry.
  • Pursue high product quality and technology innovation.
  • Offer best formula solution from practical perspective.
  • Free sample examination for all products.
  • Mature export sales team and guaranteed services.

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