PET plastic injection blown-plastic cosmetic tube process characteristics and process parameter setting skills

2021-11-08

The application range of plastic cosmetic tubes is very wide. At present, how much do you know about PET plastics. Today, cosmetic tube manufacturers take you to reveal the characteristics of PET plastic injection blown plastic cosmetic tubes and the production process of PET raw materials.

Injection molding process of polyethylene terephthalate (PET)

The chemical name of PET is polyethylene terephthalate, also known as polyester. GF-PET is currently the most used in wholesale plastic cosmetic tubes.

The rheology of PET in the molten state is better, and the pressure has a greater influence on the viscosity than the temperature. Therefore, the pressure is mainly used to change the fluidity of the melt.

1. Treatment of plastics

Because PET macromolecules contain fat bases and have a certain degree of hydrophilicity, pellets are more 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. Therefore, the manufacturer must dry the material before processing the cosmetic tube. The drying temperature is 150°C for more than 4 hours, generally 170°C for 3-4 hours. The air shot method can be used to check whether the material is completely dry. Generally, the proportion of recycled materials should not exceed 25%, and the recycled materials must be thoroughly dried.

2. Selection of injection molding machine

Because PET has a short stabilization time after melting point and 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 cut material) cannot be less than the machine injection 2/3 of the amount. Based on these requirements, cosmetic tube manufacturers have developed small and medium-sized PET plasticization systems in recent years. The clamping force is selected as greater than 6300t/m2.

3. Mold and gate design

PET plastic cosmetic tube embryos are generally formed by hot runner molds. It is better to have a heat insulation board between the mold and the injection molding machine template, the thickness of which is about 12mm, and the heat insulation board must be able to withstand high pressure. Exhaust must be sufficient to avoid local overheating or chipping, but the depth of the exhaust port should generally not exceed 0.03mm, otherwise it is easy to produce flash.

4. Melting temperature of plastic cosmetic tube

It can be measured by air shot method. The temperature ranges from 270-295°C, and the enhanced GF-PET can be set at 290-315°C.

5. Production injection speed of plastic cosmetic tube

Generally, the injection speed should be fast to prevent premature coagulation during injection. But too fast and high shear rate make the material fragile. Injection is usually completed within 4 seconds.

6. Back pressure of plastic cosmetic tube

The lower the better, so as to avoid wear. Generally not more than 100bar. Usually don't need to be used.

7. Retention time of plastic cosmetic tube

Do not use an excessively long residence time to prevent the molecular weight from decreasing. Try to avoid temperatures above 300°C. If the downtime is less than 15 minutes. Only need to do air injection treatment; if it exceeds 15 minutes, clean with viscosity PE, and reduce the barrel temperature to PE temperature until the machine is turned on again.

8. Precautions for the production of plastic cosmetic tubes

⑴Recycled material should not be too large, otherwise it is easy to cause "bridging" at the feeding place and affect plasticization. ⑵If the mold temperature is not well controlled or the material temperature is not properly controlled, it is easy to produce "white fog" and opacity. The mold temperature is low and uniform, the cooling rate is fast, and the product is transparent with less crystallization.

Today, cosmetic tube manufacturers mainly introduce the main characteristics of PET plastic cosmetic tubes.

The appearance of the plastic cosmetic tube mouth of the PET plastic cosmetic tube is relatively neat. The end surface of the plastic cosmetic tube mouth is very flat, the thread is relatively complete, there is no damage gap, and its crystallinity is very good. In the case of beneficial materials, there will be no snagging phenomenon.

The entire plastic cosmetic tube will not be deformed, and there will be no oil stains inside. The plastic cosmetic tube has a very good molding degree and high transparency. There are no black spots, scratches, fogging, whitening, or hardening. The colored plastic cosmetic tube should be relatively uniform in color. Any obvious color difference will work. The bottom of the plastic cosmetic tube is not dented, and there is no bulge. The bottom of the plastic cosmetic tube has no cracks or delamination.

Both PET plastic cosmetic tube and PP plastic cosmetic tube are plastic products, but there are also big differences between them. PP plastic cosmetic tube is a kind of non-toxic food container, its high temperature resistance performance is very good, can be used as cosmetic packaging shell, plastic cosmetic tube and other skin care container can use it. However, the high temperature resistance of PET plastic cosmetic tube is not as good as that of PP plastic cosmetic tube, and the carbonated cosmetics that cosmetic tube manufacturers usually drink, such as the packaging plastic cosmetic tubes of skin care products, are made of it.

Any kind of plastic product has a temperature limit when it is used. If the temperature is too high, it will decompose a harmful substance, or the plastic made by the cosmetic tube will be easily softened. Most of all plastic products are toxic substances. There are many cosmetic plastic cosmetic tubes and liquid packaging plastic cosmetic tubes used by cosmetic tube manufacturers that are not resistant to high temperatures. Therefore, cosmetic tube manufacturers need to pay attention when using it. There are also some special numbers on the bottom of the plastic cosmetic tube. Plastic cosmetic tubes with the number six or three inside must not use these cosmetics because they are poisonous.