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What are the choices of additives in PVC pipe production line?

Time:2019-04-15

In the production process of PVC pipe production line, we need to use additives. What are the additives?

1. It is necessary to add a proper amount of stabilizer to the thermosensitive resin during the forming process.

When choosing several stabilizers at the same time, we should pay attention to the synergistic effect between them.

In addition, attention should also be paid to the amount of stabilizer, excessive stabilizer will make the rheological properties of plastic melt worse.

2. Adding appropriate lubricant to the formulation can not only improve the moulding properties of the resin, but also reduce the thermal decomposition of the resin, and improve the gloss and other physical and mechanical properties of the product surface due to the improvement of fluidity.

In selecting lubricants, special attention should be paid to the compatibility with resins and the balance of lubrication between internal and external lubricants [2].

3. Plasticizer, which can reduce the melting viscosity and melting temperature of polymers, increase plasticity and fluidity, and make products flexible. After plasticizing, although the brittleness of the product is improved obviously, and the flexibility and elongation are also improved, the hardness, tensile strength and elastic modulus of the product will decrease.

4. Colorant Firstly, the addition of colorant should be based on the specific conditions of plastics in the preparation and moulding process. For example, when forming PVC bellows, because PVC will release HCl in the process of forming, it is not appropriate to select acid-sensitive cadmium red, group green, etc.

Secondly, the selected colorant should also have good compatibility with the resin and be evenly dispersed in the resin. Thirdly, the influence on the forming machinery and mould should be considered.

In the process of melting and moulding of plastics, the deposits of plastics or colorants containing colorants on the die or die surface will cause defects on the surface of products, change the cross section of extrudates, and even produce waste products.

In addition, colorants also have a certain impact on product forming, especially for crystalline resins.

5. The increase of filler-filler can improve the impact strength and elongation at break of products, but it can reduce the tensile strength and flexural modulus of products. When a large number of fillers are added, it will also reduce the formability, abrasion equipment and affect the surface gloss of products.

The particle size of filler also has a great influence on the mechanical properties of products. Plastic corrugated pipe has thin wall, small gap between pipe and die, and large resistance of machine head.

Generally, it is not suitable to add fillers that affect material flow performance in the formulation. However, in order to improve the rigidity and strength of corrugated pipe and reduce the production cost, the treated active calcium carbonate or calcium carbonate treated with phthalate coupling agent are often used as fillers.

6. In the production of bellows, other additives, especially double-walled bellows, require high impact strength. Therefore, most of them adopt the method of adding impact modifier in the formulation.

The impact modifier can improve the impact strength, elongation at break and other toughness indicators, but the tensile strength, flexural modulus of elasticity and other rigidity indicators decrease.