Because of its low price, PVC material has inherent anti-inflammatory properties, is strong and strong, has good chemical resistance, and has a shrinkage rate of 0.2-0.6%. Products are increasingly used in electrical appliances, machinery, construction, daily necessities, toys, and packaging. According to characteristics of PVC material, injection molding process of product is analyzed as follows:

 

Thermal stability of PVC is poor, molding temperature is close to decomposition temperature, fluidity is not good, and appearance is easy to form defects. Additives are generally required to increase its fluidity, and its strength, electrical insulation, and chemical resistance are good.

In order to shorten injection molding cycle, the shorter injection port, the better, cross-section should be circular, minimum diameter of nozzle opening is 6 mm, cone is circular, and internal angle is 5 degrees. It is best to add a cold well and cold material. Well can prevent poorly melted semi-solid materials from entering mold cavity, these materials will affect surface modification and strength of product.
Draft angle should be between 0.50 and 10 to ensure that there is enough venting equipment in \cavity. Commonly used vent size is 0.03-0.05mm deep and 6mm wide, or perimeter clearance of each thimble is 0.03-0.05 mm. Mold should be made of stainless steel or plated with hard chrome.

PVC is a heat-sensitive plastic. Overheating or excessive shearing will cause decomposition and spread rapidly, because one of decomposition products (such as acid or HCI) will have a catalytic effect, causing process to further decompose, acid will attack metal and make it change. If it becomes dents, it will peel off protective layer of metal, causing rust, which is even more harmful to human body.
Common screw length to diameter ratio is 18-24:1, three-stage ratio is 3:5:2, and compression ratio is 1.8-2. When screw is in place, distance between tip and nozzle should be 0.7-1.8mm. Screw must be made of stainless steel or chrome-plated.
Screw gasket: Screw gasket is between 2mm and 3mm, larger machines will be larger.
Injection volume: Actual retention time of cylinder should not exceed 3 minutes.
Barrel temperature setting: Temperature provided can only be used as a reference. Make appropriate adjustments according to actual conditions of machine and raw materials, or it may exceed recommended range.
Barrel residence time: under temperature control of 2000C (compound), barrel residence time can exceed 5 minutes at most.
Injection speed: Injection speed should be slow, otherwise excessive shearing will degrade material. When using UPVC to produce extremely smooth thick-walled products, multi-level injection speeds should be used. If light brown stripes radiate from gate, it means injection speed is too fast.
Back pressure: Commonly used surface value is 5bar. Increasing back pressure is conducive to color mixing and exhaust, but back pressure should be as low as possible.
Shutdown: Due to low overheating stability of PVC, shutdown part is very important. Clean barrel without leaving any PVC. Other thermoplastics with high overheating stability but not resistant to PVC can be used (such as PMMA, PP, LDPE, or GPPS), do not mix POMTUPVC in same barrel, otherwise it will cause excessive chemical reaction and cause serious damage to machine.
Mixing ratio: Maximum mixing ratio of nozzle material is 20%, otherwise it will affect product quality.