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Do You Know How Pvc Is Injection Molded?

May. 09, 2020

 Do you know how PVC is Injection Molded? Precision plastic extrusion part supplier to share with you.

Due to its low price, PVC materials are inherently anti-inflammatory, strong and strong, and have good chemical resistance. The contraction rate was 0.2-0.6%. Products are increasingly used in electrical appliances, machinery, construction, daily necessities, toys, and packaging. According to the properties of the PVC material, analysis for the process of injection molding products are as follows: the characteristics of PVC material PVC thermal stability is poor, the molding temperature is close to the decomposition temperature, liquidity is poor, prone to defects, PVC material heat resistance is poor, the easiest to coking, acid gases and corrosion of the mold, can be in the process of processing plasticizing additive increase its liquidity is strong, generally need to add additives to use, its strength, electrical insulation, chemical resistance is very good.

Mold and gate design

In order to shorten the injection molding cycle, the shorter the nozzle, the better. The cross-section should be circular. The diameter of the nozzle orifice shall be at least 6 mm. It should be tapered, with an internal Angle of 5 degrees. It is best to add a cold well. The holes prevent semi-solid materials with different melting points from entering the cavity, which will affect surface modification and product strength. The drawing Angle should be between 0.50 and 10 to ensure adequate exhaust in the cavity. The commonly used vent sizes are 0.03-0.05mm deep and 6mm wide, or the clearance around each thimble is 0.03-0.05mm. The mold shall be made of stainless steel or hard chromium plated.

Pvc Plastic Extrusion Profile

Pvc Plastic Extrusion Profile

The molding process of PVC plastic extrusion profile

PVC is a heat-sensitive plastic.

Overheating or excessive shearing can lead to decomposition and rapid diffusion, as one of the decomposition products (such as an acid or HCl) will catalyze the process, which will lead to further decomposition, while the acid will erode the metal and alter the formation of pits. It can cause the metal protective layer to peel off, causes the rust, is more harmful to the human body.1. Screw pad: the screw pad is between 2 and 3mm, and the greater the chance is.2. Sample quantity: the actual cylinder stay time should not exceed 3 minutes.3. Barrel temperature setting: the temperature provided is only for reference, which can be adjusted according to the actual conditions of the machine and raw materials. It may also go beyond the recommendations.4. Barrel holding time: under the temperature control of 2000℃ (rubber), the barrel holding time can exceed 5 minutes at most.5. Injection speed: the injection speed should be slow, otherwise excessive shear force will degrade the material. When using UPVC to produce extremely smooth thick wall products, the multi-stage injection rate should be used. Light brown streaks on the door indicate fast shooting.6. Backpressure: the commonly used surface value is 5 bar. Increasing back pressure is good for color mixing and exhaust, but the lower the backpressure, the better.


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