Because of its low price, PVC pellets are inherently anti-inflammatory, strong and strong, chemically resistant, and shrinkage is 0.2-0.6%. The products are widely used in electrical appliances, machinery, construction, daily necessities, toys and packaging. For the characteristics of PVC materials, the injection molding process of the products is as follows:

Characteristics of a PVC material
The thermal stability of PVC is poor, the molding temperature is close to the decomposition temperature, the fluidity is not good, the appearance is easy to form poor defects, the heat resistance of PVC material is not good, the most easy to burn, acid gas is generated and the mold is corroded, and plasticization can be added during processing. The agent increases its fluidity and generally needs to be added with additives, and its strength, electrical insulation and chemical resistance are good.

Two mold and gate design
In order to shorten the injection molding cycle, the shorter the nozzle, the better, the cross-section should be round, the diameter of the nozzle mouth is at least 6 mm, the cone is rounded, and the inner angle is 5 degrees. It is best to add cold wells and cold materials. The well prevents the poorly melted semi-solid material from entering the mold cavity, and the materials affect the surface modification and the strength of the product.
The draft angle should be between 0.50 and 10 to ensure that there are enough exhaust equipment in the cavity. The commonly used vent size is 0.03-0.05mm deep, 6mm wide, or the gap between each thimble is 0.03-0.05. Mm. The mold is made of stainless steel or hard chrome plated.

Three PVC molding process
PVC is a heat-sensitive plastic. Excessive or excessive shearing will cause decomposition and spread quickly, because one of the decomposition products (such as acid or HCI) will cause catalysis, causing the process to further decompose, and the acidic substance will corrode the metal and make it change. Forming a depression will cause the protective layer of the metal to peel off, causing rust and being more harmful to the human body.
The common screw length to diameter ratio is 18 to 24:1, the three ratio is 3:5:2, and the compression ratio is 1.8 to 2. The recommended groove depth of the feed section is as follows:
Screw diameter (mm) 35506075100
Groove depth (mm) 23456
The tip of the screw should have an internal angle of 25 to 30 degrees. When the screw is in place, the distance between the tip and the nozzle should be 0.7 to 1.8 mm. The screw must be made of stainless steel or chrome plated.
1) Screw padding: The screw padding is between 2 and 3 mm, and the large-scale opportunity is larger.
2) Injection volume: The actual cylinder retention time cannot exceed 3 minutes.
3) Barrel temperature setting: The temperature provided can only be used as a reference. It can be adjusted according to the actual conditions of the machine and raw materials, and may exceed the recommended range.
The injection volume of the intermediate feed section temperature (0C) in the front section of the position of the mold nozzle is 20-85% of the theoretical injection volume of the machine. The smaller the actual injection volume, the longer the residence time of the material and the risk of degradation after heating. The greater the sex.
4) Retention time of the barrel: Under the temperature control of 200 degrees Celsius (the compound), the retention time of the barrel can be more than 5 minutes.
5) Injection speed: the injection speed should be slow, otherwise excessive shear will degrade the material. When UPVC is used to produce extremely smooth thick-walled products, multi-stage injection speed should be used. If light brown stripes are emitted from the gate, Indicates that the shot speed is too fast.
6) Back pressure: The commonly used surface value is 5 bar. Increasing the back pressure is good for color mixing and exhausting, but the lower the back pressure should be.
7) Shutdown: Due to the low thermal stability of PVC, it is very important to stop the machine. It is necessary to clean the barrel without leaving half of PVC particles. Other thermoplastics with high stability and resistance to PVC can be used (for example, PMMA). , PP, LDPE, or GPPS), should not mix POMTUPVC in the same barrel, otherwise it will lead to excessive chemical reaction, causing serious damage to the machine.
8) Mixing ratio: The maximum mixing ratio of the nozzle material is 20%, otherwise it will affect the quality of the product.
9) Typical products: The main purpose of UPVC is to manufacture drainage pipes, or the casing of computer and television, water filter groove, photocopying machine casing, electric meter and gas casing, transparent cover of printing machine, communication style and various electronic parts. Wait.

Wuxi Jiahong Plastics Technology Co., Ltd. has nearly 30 years of experience in research and development and granulation of modified PVC pellets. The professional technical service team can provide one-stop system solutions for customers. For more information about the product, please visit our official website: www.sdbzkt.cn, consult online customer service or call the hotline. Fixed line: 0510-68755207 Mobile: 15190220696, we will be happy to help you.

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