Analysis of injection Molding process of PET Plastics

PET plastic injection molding process is one of the very important technical processes in plastic processing. For PET plastic bottles, plastic packaging factories will use blow molding in most cases, but injection molding process has special processing advantages. For PET injection molding, technicians need to consider many factors, as follows. 

Introduction to PET Plastics: 

PET chemistry is called poly (ethylene terephthalate), also known as polyester. 

At present, the most commonly used in customers is GF-PET, mainly bottle embryo. 

The rheological property of PET is better in the melting state, and the effect of pressure on viscosity is greater than that of temperature. Therefore, the fluidity of melt is mainly changed by pressure. 

Chemical and physical properties of PET: 

The glass transition temperature of PET is about 165C, and the crystallization temperature range of the material is 120 ~ 220C. 

PET has strong hygroscopicity at high temperature. 

For glass fiber reinforced PET materials, bending deformation is very easy to occur at high temperature. 

The crystallization degree of the material can be improved by adding crystallization enhancer. 

Transparent products processed with PET have glossiness and thermal distortion temperature. 

Special additives such as mica can be added to PET to minimize bending deformation. 

If a lower mold temperature is used, transparent products can also be obtained using unfilled PET materials. 

Injection molding process: 

Injection molding is mainly used to enhance the molding of PET. 

Screw injection machines are usually used. 

The screw generally needs to be hardened to avoid wear after long-term use. 

The length of the nozzle hole of the injection machine should be as short as possible, and its diameter should be controlled around 3mm. 

The melting point of the reinforced PET is as high as 260C. In order to prevent the nozzle from clogging, a heater with higher power should be installed. 

In addition, the tip of the nozzle hole is preferably processed into the reverse cone shown in figure-1, so that the molten material in the flow channel and the nozzle can be easily cut off.

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