Several key factors of nano-calcium carbonate determining rubber properties

The benefits of calcium carbonate in rubber can be summarized as cost reduction, efficiency enhancement, and performance improvement, which are specifically reflected in the following aspects:

Significantly reducing production costs: This is the primary benefit. The price of calcium carbonate is much lower than that of mainstream reinforcing agents such as carbon black and silica white. Adding it in large quantities as a filler can directly reduce the cost of rubber compounds.

Improve the processing technology:

Mixing: easier dispersion, shorter mixing time, and reduced energy consumption.

Extrusion/Calendering: The fluidity of the rubber compound improves, resulting in a smoother surface and more stable dimensions of the product.

Vulcanization: Some activated calcium carbonate can accelerate the vulcanization rate and improve production efficiency.

Enhance specific physical properties:

Ordinary calcium carbonate: It mainly serves as a filler and extender.

Nano-calcium carbonate: It exhibits semi-reinforcing or reinforcing effects, enhancing the tensile strength, tear strength, and wear resistance of rubber, while imparting higher dimensional stability to the products.

Endow with special functions or appearance:

Coloration: White calcium carbonate can be used to manufacture light-colored or colored rubber products, and can also partially replace expensive titanium dioxide.

Compatibility enhancement: It has a compatibilizing effect on certain synthetic rubbers, improving the uniformity of the rubber compound.

Adjusting hardness and stiffness:

Increasing the amount of calcium carbonate can enhance the hardness and stiffness of rubber products, making them less prone to deformation. This is suitable for products such as shoe soles and hoses.

The quality factors affecting the filling effect of nano-calcium carbonate in rubber mainly include the following aspects:

Polymorph

Among different crystal forms of nanometer calcium carbonate, chain-like nanometer calcium carbonate has the best reinforcing effect on rubber.

Particle Size

In the application of nano-calcium carbonate in rubber, the finer the particles, the larger the specific surface area for mutual infiltration with rubber, making it increasingly difficult for calcium carbonate particles to disperse. Especially when the particle size is below 80nm, due to the increase in surface energy, heat generation during rubber mixing can easily lead to sticky mixing.

Oil Absorption Value

The higher the oil absorption value of nano-calcium carbonate used in rubber, the better the wettability and reinforcing effect of calcium carbonate on rubber.

Moisture

As a filler for rubber, the reduction in moisture content of nano-calcium carbonate leads to a shorter scorch time during vulcanization, which is beneficial for increasing the vulcanization rate.

PH value

The pH value of nano-calcium carbonate primarily influences its vulcanization rate in rubber applications. Generally, the pH range for nano-calcium carbonate is recommended to be 9-10.5. A higher pH value promotes vulcanization, whereas a lower pH value results in a slower vulcanization rate and longer scorch time, thereby extending processing time and increasing energy consumption.

Nanometer calcium carbonate, as a novel inorganic filler, holds significant application prospects in rubber products. Nowadays, with the continuous advancement of technology, the application prospects of nanometer calcium carbonate in rubber products will become even broader.