Which materials have an impact on PVC hose?

Which materials have an impact on PVC hose?

1PVC resin: Generally speaking, the use of PVC resin with relatively high molecular weight and relatively narrow molecular weight distribution can obtain good physical and mechanical properties, thermal stability and good surface uniformity. But this will increase the calendering temperature and equipment load, which will be more unfavorable to the production of thinner film. Therefore, in the formulation design of calendering products, the advantages and disadvantages should be weighed and proper resin should be used. The content of ash, moisture and volatiles in the PVC resin can not be too high. The high ash content will reduce the transparency of the film, while the high moisture and volatile matter will make the products with bubbles.

2 other components: plasticizers and stabilizers are other components that affect the calendering in the formulation. The more the plasticizer, the lower the viscosity of the material. Therefore, the roller speed can be increased or the calender temperature can be increased without changing the load of the calender.

The use of improper stabilizers often makes a layer of wax like material on the surface of the roller roller, making the surface of the film not light, producing sticky rolls in production or changing the product. The higher the calendering temperature, the more serious this phenomenon. The reason for the appearance of wax like substance is that the compatibility of the stabilizer and PVC resin is poor and the positive electricity of its molecular polar group is high, so that the pressure delay is squeezed out to form the waxy layer on the surface of the roller. Pigments, lubricants, chelating agents and other raw materials may also form wax layers, but they are less important.

The ways to avoid wax formation are as follows: (1) choose suitable stabilizer. Generally speaking, the higher the positive polarity of polar groups in stabilizer molecules is, the easier they are to form wax layers. For example, barium soap is more serious than cadmium soap and zinc soap, because the positive electricity of barium is high, cadmium is smaller and zinc is smaller, so the calender formula should control the amount of barium soap. In addition, liquid stabilizers such as ethyl hexanoate and naphthenic salts should be used less or without laurate. (2) adding stronger filler such as hydrous alumina to absorb metal soap. 3. Add acid lubricants, such as stearic acid, etc. The acid lubricant has a stronger affinity to the metal. It can first occupy the surface of the roller and lubricate the stabilizer, so it can prevent the stabilizer from sticking to the roller surface. However, the amount of stearic acid can not be too much, otherwise it will easily precipitate from the film.

3 pre mixing and plasticizing of materials: mixing and plasticizing are aimed at dispersing and plasticizing the components of plastics evenly. Uneven dispersion often results in fish eyes, poor flexibility and other quality defects. Uneven plasticization will result in spots on the films. The plasticizing temperature should not be too high and the time should not be too long. Otherwise, too much plasticizer will be lost and the resin will decompose. The temperature should not be too low, otherwise there will be no roll or plasticizing. The suitable plasticizing temperature depends on the specific formula, generally 150-180 degrees.

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