What are the elements of plastic preform molding?

The main elements of Plastic Preform molding include plastic processing, selection of injection molding machines, design of molds and gates, etc. Only by properly handling these elements can we produce high-quality products. However, sometimes there will be some quality defects, such as yellowing of the preform, excessive change rate of wall thickness, etc., which need to be discovered and solved in time to avoid affecting its normal use. The following is an introduction to the elements of Plastic preform molding and common quality defects. Let's take a look.

What are the elements of plastic preform molding?
1. Plastic processing
Since PET macromolecules contain lipid groups and have a certain degree of hydrophilicity, pellets are sensitive to water at high temperatures. When the moisture content exceeds the limit, the molecular weight of PET decreases during processing, and the product becomes colored and brittle. Generally, the proportion of preform recycled materials should not exceed 25%, and the recycled materials should be completely dried.

2. Selection of injection molding machine
Due to the short stable time of PET after the melting point and the high melting point, it is necessary to choose an injection system with more temperature control sections and less self-friction heat generation during plasticization, and the actual weight of the product (water-containing material) should not be less than machine injection. 2/3 of the amount.

3. Residence time
Do not use too long residence time to prevent the decrease of molecular weight, and try to avoid the temperature above 300°C. If the machine is shut down for less than 15 minutes, it only needs to be treated with air injection; if it is more than 15 minutes, it must be cleaned with viscosity PE, and the temperature of the machine barrel should be lowered to the PE temperature until it is turned on again.

4. Mold and gate design
Preforms are generally formed by hot runner molds. It is better to have a heat shield between the mold and the template of the injection molding machine. Its thickness is about 12mm, and the heat shield must be able to withstand high pressure. The exhaust must be sufficient to avoid local overheating or fragmentation, but the depth of the exhaust port should generally not exceed 0.03mm, otherwise flashing will easily occur.

Heshan Yecheng Plastic Products Co.,Ltd. was established in 2001, covers an area of 30,000 ㎡ with more than 300 staff. After 20+ years of unremitting efforts, we now become the leading manufacturer of PET preform in China. Products are mainly used for cosmetics, mineral Water preform & beverage, pesticide, oil bottles, Cream Jar. etc.

For more details about the product, please contact us:
Tel: +86-0750-8977221/8977215
Mobile: +860086-13822396030
Mail: admin@hsyecheng.com