Practical experience in the application of calcium carbonate, talc, quartz powder and other fillers in PVC

Fillers are commonly used additives for PVC, especially in PVC hard products such as plates, tubes and profiles. In PVC soft products such as cable materials, fillers are often added. In addition to the purpose of initially reducing the cost, the purpose of adding fillers is to develop more functional trends, such as increasing the hardness, electrical insulation, heat resistance, and reduction of molding shrinkage of the product.

PVC has good compatibility with most fillers, and the filler can be selected in a wide range and added in a large amount. Commonly used powder fillers include: calcium carbonate, kaolin, talc and wollastonite; industrial waste such as fly ash, red mud, mica and wood flour.

Among them, calcium carbonate is most commonly used. In PVC hard products, heavy and light calcium carbonate are used, and some high-grade products also use nano-calcium. In soft PVC products, heavy calcium or light calcium must be selected according to product requirements.

Here are some practical experiences of downstream applications for reference:

1, PVC floor fillers are used in a large amount, generally ordinary floor, calcium carbonate can be added in amounts of 150 to 200, the fineness is generally 400 mesh; some special requirements of the floor will also use wollastonite and talcum powder, the amount of 10 To 20, there are also companies that have joined quartz sand.

2. For PVC products with high electrical performance requirements for cable materials, kaolin (calcined clay) is generally used as filler. Kaolin can improve the electrical insulation of PVC. Even if calcium carbonate is added, the amount of addition should be less than 10 parts, otherwise the electrical properties will not be worth the loss. The fineness is generally selected from calcium powder with a content of more than 2000 mesh and a high content of 2 um.

3. In the PVC calendered products, the addition of ultrafine talc powder can improve the processing lubricity. At present, calcium carbonate powder is also often used for calendered products, and the fineness is selected to be about 1,250 mesh.

4. The amount of PVC paste resin added to the filler should not exceed 10 parts, otherwise the viscosity increase of the paste will cause molding difficulties. Calcium carbonate or quartz powder is used depending on the application.

In general, in addition to the variety and dosage according to the downstream demand, the PVC filling formula should also pay attention to the oil absorption of the filler, and add suitable and quantitative plasticizers and additives.

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