What are the precautions for injection molding of pet plastic preforms?
- Categories:News
- Time of issue:2021-05-21 11:47
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(Summary description)From the scientific name, everyone does not necessarily know what pet plastic preforms are. In fact, the chance of us seeing pet plastic preforms in life is still quite large, let's take a look at pet plastic preforms. PET plastic preform is a typical injection molding product, which is easy to transport. It is mostly made of plastic material with uniform texture and good insulation. It is an intermediate product for plastic bottles and oil drums. In general, the following issues should be paid attention to in the injection of pet plastic preforms: 1. Plastic processing: Because PET macromolecules contain fat base, which has certain hydrophilicity, pellets are more sensitive to water at high temperature. When the moisture content exceeds the limit, the molecular weight of PET will decrease during processing and the product will become colored. , Become brittle. Because of this, the materials must be dried before processing. The drying temperature is 150°C for more than 4 hours, generally 170°C for 3-4 hours. 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: Since PET has a short stable time after melting point and high melting point, it is necessary to select an injection system with more temperature control sections and less self-friction heat generation during plasticization, and the product (water-containing material) The actual weight cannot be less than 2/3 of the injection volume of the machine. 3. Mold and gate design: PET preforms are generally formed by hot runner molds. There must be a heat shield between the mold and the injection molding machine template, the thickness of which is about 12mm, and the heat shield 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: 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. Injection speed: 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: The lower the better, so as to avoid wear. Generally not more than 100bar. Usually don't need to be used. 7. Retention time: Do not use too long retention time to prevent molecular weight drop. 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. Although the injection molding process of pet plastic preforms is not complicated, the quality of pet plastic preforms is closely related to the injection molding process. Understanding the above precautions can help you inject better pet plastic preforms.
What are the precautions for injection molding of pet plastic preforms?
(Summary description)From the scientific name, everyone does not necessarily know what pet plastic preforms are. In fact, the chance of us seeing pet plastic preforms in life is still quite large, let's take a look at pet plastic preforms. PET plastic preform is a typical injection molding product, which is easy to transport. It is mostly made of plastic material with uniform texture and good insulation. It is an intermediate product for plastic bottles and oil drums. In general, the following issues should be paid attention to in the injection of pet plastic preforms:
1. Plastic processing: Because PET macromolecules contain fat base, which has certain hydrophilicity, pellets are more sensitive to water at high temperature. When the moisture content exceeds the limit, the molecular weight of PET will decrease during processing and the product will become colored. , Become brittle. Because of this, the materials must be dried before processing. The drying temperature is 150°C for more than 4 hours, generally 170°C for 3-4 hours. 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: Since PET has a short stable time after melting point and high melting point, it is necessary to select an injection system with more temperature control sections and less self-friction heat generation during plasticization, and the product (water-containing material) The actual weight cannot be less than 2/3 of the injection volume of the machine.
3. Mold and gate design: PET preforms are generally formed by hot runner molds. There must be a heat shield between the mold and the injection molding machine template, the thickness of which is about 12mm, and the heat shield 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: 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. Injection speed: 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: The lower the better, so as to avoid wear. Generally not more than 100bar. Usually don't need to be used.
7. Retention time: Do not use too long retention time to prevent molecular weight drop. 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.
Although the injection molding process of pet plastic preforms is not complicated, the quality of pet plastic preforms is closely related to the injection molding process. Understanding the above precautions can help you inject better pet plastic preforms.
- Categories:News
- Author:
- Origin:
- Time of issue:2021-05-21 11:47
- Views:
From the scientific name, everyone does not necessarily know what pet plastic preforms are. In fact, the chance of us seeing pet plastic preforms in life is still quite large, let's take a look at pet plastic preforms. PET plastic preform is a typical injection molding product, which is easy to transport. It is mostly made of plastic material with uniform texture and good insulation. It is an intermediate product for plastic bottles and oil drums. In general, the following issues should be paid attention to in the injection of pet plastic preforms:
1. Plastic processing: Because PET macromolecules contain fat base, which has certain hydrophilicity, pellets are more sensitive to water at high temperature. When the moisture content exceeds the limit, the molecular weight of PET will decrease during processing and the product will become colored. , Become brittle. Because of this, the materials must be dried before processing. The drying temperature is 150°C for more than 4 hours, generally 170°C for 3-4 hours. 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: Since PET has a short stable time after melting point and high melting point, it is necessary to select an injection system with more temperature control sections and less self-friction heat generation during plasticization, and the product (water-containing material) The actual weight cannot be less than 2/3 of the injection volume of the machine.
3. Mold and gate design: PET preforms are generally formed by hot runner molds. There must be a heat shield between the mold and the injection molding machine template, the thickness of which is about 12mm, and the heat shield 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: 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. Injection speed: 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: The lower the better, so as to avoid wear. Generally not more than 100bar. Usually don't need to be used.
7. Retention time: Do not use too long retention time to prevent molecular weight drop. 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.
Although the injection molding process of pet plastic preforms is not complicated, the quality of pet plastic preforms is closely related to the injection molding process. Understanding the above precautions can help you inject better pet plastic preforms.
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