Because PET macromolecules contain lipid groups and have certain hydrophilicity, they are very sensitive to water when PET is used to make Pet Preform Mould. If the water content is not controlled, it will eventually make the products crisp. Become unqualified and the quality is not good. The drying temperature is 150 degrees Celsius and exceeds 4 hours. The temperature is usually 170 ° C and 3-4 hours. Air can be used to check if the material is completely dry.

The proportion of recycled materials should not exceed 25%, and the recycled materials should be thoroughly dried.

2, choose injection molding machine

Since PET has a stable melting point and a high melting point in a short time, temperature control is selected, and more self-plastic injection molding systems have less friction heat, and the actual weight of the product (outlet) is not less than 2/3 of the number of injection molding machines. Based on these requirements, Ramada has developed a series of small and medium-sized PET special plasticizing systems in recent years. The clamping force is greater than 6300t / m2.

3, mold and gate design

PET preforms are typically molded using hot runner molds. It is preferable to provide a heat shield between the mold and the injection molded plate to a thickness of about 12 mm, and the heat shield can withstand high pressure. Exhaust must be sufficient to avoid local overheating or breakage, but the exhaust depth is generally not more than 0.03mm, otherwise it is easy to produce flash.

4, melting temperature

Measured by aerial shot. The difference of 270-295 degrees, the enhanced grade GF-PET can be set to 290-315 degrees and the like.

5, injection speed

In general, the injection speed is fast and prevents premature coagulation during injection. However, the speed is too fast, the shear rate is high, and the material is brittle. The lens is usually completed in 4 seconds.

6, back pressure

The lower the better, to avoid wear. Generally no more than 100bar. Usually not necessary to use.

7. Retention time

Do not use excessive residence times to prevent molecular weight loss. Try to avoid temperatures above 300 degrees Celsius. If the stop time is less than 15 minutes. For empty processing only; if it is more than 15 minutes, use viscosity PE cleaning and adjust the cylinder temperature to PE temperature until it is turned on.

8, matters needing attention

The recycled material should not be too large, otherwise it will easily produce a "bridge" and plasticizing effect on the material.

Nowadays, many China Pet Bottle manufacturers have realized this problem. They have become very noticeable in the process of mold making. The molds produced are low and uniform in temperature, fast in cooling, less in crystallization, and transparent in products. It is more popular with customers in the world market.