The main properties and molding process of polyethylene (PE)

Polyethylene (PE), commonly known as "flower material", is a crystalline plastic. Its main properties and uses are as follows:

    1. Purpose: Lining of chemical equipment and storage tanks. Chemical corrosion-resistant pipelines. Valves. Bushings. Roller pivots to replace copper and stainless steel.

    2. Polyethylene is often used for blow-molded products.

    3. The mechanical strength is not high. The heat distortion temperature is low, and the surface is easy to scratch.

    4. Polyethylene is a semi-transparent particle, and the rubber parts are milky white in appearance.

    5. Polyethylene has softness, impact resistance, extensibility and abrasion resistance, and good low-temperature toughness.

    6. It is insoluble in any solvents at room temperature. The chemical properties are stable. On the other hand, PE is difficult to bond.

    7. Polyethylene is divided into high-density polyethylene (HDPE) (hard soft rubber) and low-density polyethylene (LDPE) (soft rubber). The transparency of the two types decreases as the density increases.

    8. Polyethylene has high molding shrinkage, high-density polyethylene (HDPE) 1.5%-4.0% (usually 2.0%). Low-density polyethylene (LDPE) 1.5%-5.0% (usually 2.0%). Commonly used inner mold material 718.

    The molding process of polyethylene (PE) is as follows:

    1. Low water absorption, no need to dry before processing.

    2. It is not suitable to use the direct feed port, which is prone to internal stress or uneven shrinkage.

    3. Due to its good quality, the overflow value is 0.02mm. The molding temperature range is wide, and it is easy to mold.

    4. Due to the softness, the forced demoulding method can be used instead of the sliding position (slider) when necessary.

    5. The injection pressure and holding pressure should not be too high to avoid deformation and cracking caused by large internal stress in the beer part. Injection pressure is 60-70Mpa.

    6. Increase the barrel temperature, the appearance quality is good, but the molding shrinkage rate is large (shrinkage rate 2.0-2.5%), the barrel temperature is too low, and the product is easy to deform (the molding with point gate is more serious, and the molding with multi-point gate can be improved Warpage). Temperature parameters: the temperature of the front barrel is 200-220¡ãC, the temperature of the middle barrel is 180-190¡ãC, and the temperature of the rear barrel is 160-170¡ãC.

    7. The temperature of the front and back molds should be the same (the mold temperature is generally 20-40¡ãC), and the cooling water channel should not be too close to the surface of the cavity, lest the local temperature difference is too large and the internal stress of the product will remain. Increase the mold temperature, the product gloss is good, but the molding cycle is long. Reduce the mold temperature, the product has good flexibility, high transparency, and high impact strength. If the mold temperature is too low, rapid cooling may cause product deformation or molecular orientation to cause delamination. In short, by adjusting the mold temperature, the hardness and flexibility of the product can be adjusted.