PET Melting Temperature and Processing Guide
Date:2024-6-03 Author:hcscrew
PET Melting Temperature and Features
PET, short for polyethylene terephthalate, is the most common type of thermoplastic polyester. Known for its versatility, PET is used in various applications due to its lightweight, semi-rigid to rigid properties, and natural transparency. Depending on its thickness, PET can range from amorphous to highly crystalline.
Key Characteristics of PET:
- – Density: 1.3-1.4 g/cm³
- – Glass Transition Temperature: 73-78°C
- – Service Temperature Range: -40°C to 140°C
- – Melting Temperature: 250°C
PET Processing Methods:
PET is hygroscopic, meaning it absorbs moisture. Therefore, pre-drying before processing is crucial to prevent defects in the final product.
Recommended Processing Techniques:
- – Injection Moulding: Ideal melt temperature is between 280-310°C. For crystalline PET, maintain mold temperatures at 140-160°C; for transparent applications, 10-50°C is best.
- – Extrusion: Melt temperatures of 270-290°C are used to produce films and sheets, which can be thermoformed later.
- – Blow Moulding: Commonly used for making transparent bottles, with mold temperatures between 10-50°C.
Key Factors in PET Plastic Extruder Screw Design:
Choosing the right PET plastic extruder screw is important for ensuring efficient processing and high-quality products.
- 1. Screw Parameter Selection: When designing screws for PET plastic extruders, the L/D (length-to-diameter) ratio is typically selected between 20:1 and 22:1. The screw is divided into three sections:
- – Feeding Section (L1): Accounts for 50-60% of the screw length.
- – Melting Section (L2): Makes up 20-30% of the screw length.
- The screw compression ratio is generally between 1.8 and 2.2 to prevent overheating, which can cause discoloration or opacity. For recycled materials (flakes), increasing the conveying capacity of the feeding section and adopting a forced-feed plasticizing system may be necessary.
- 2. Screw Construction: The PET plastic extruder screw typically consists of five sections:
- – Feed Section: Ensures steady material intake.
- – Melting Section: Compresses and pre-melts the material.- Extruding Section: Ensures uniform material flow.
- – Barrier Section: Enhances melting efficiency.
- – Mixing Section: Improves material homogeneity.
- Each section plays a vital role in the mixing, melting, and plasticizing process of PET material.
- 3. Screw-to-Barrel Clearance: Due to PET’s low viscosity, maintaining minimal clearance between the screw and barrel is essential to reduce material leakage and degradation during processing.
- 4. Screw L/D Ratio: For PET plastic extruder screws, an L/D ratio between 23:1 and 25:1 is recommended. The screw diameter typically ranges from 50mm to 120mm. This design helps improve the plasticizing rate and overall product quality.
Optimizing Screw Design for PET Processing:
- – Compression Ratio: Selecting an appropriate compression ratio (1.8-2.2) ensures efficient material processing without causing any material degradation.
- – Feed System: For recycled PET materials, an enhanced feed system, such as forced-feed plasticizing, may be required to accommodate the increased conveying capacity.
- – Precision Engineering: Ensuring precise engineering and minimal clearance between the screw and barrel reduces PET degradation risk and promotes high-quality extrusion.
Key Strengths:
- – Excellent wear resistance and electrical properties
- – Low coefficient of friction and high flexural modulus
- – Superior dimensional stability and transparency to microwave radiation
- – FDA compliant with high strength and stiffness compared to PBT
- – High HDT and long-term use temperature among engineering thermoplastics
Limitations:
- – Slow crystallization rate, making it unsuitable for outdoor use or hot water applications
- – Burns poorly and does not mold as well as PBT
Applications
PET is widely used in various industries due to its durability and versatility. Here are some common applications:
- – Bottles for mineral water and soft drinks
- – Cosmetic jars and microwaveable containers
- – Transparent films and electrical plugs
- – Housings for appliances and flexible food packaging
- – Thermal insulation and magnetic tape
- – Packaging trays and blisters
- – Thermoformed food containers and disposable coffee cups
Conclusion
Understanding the melting point of PET plastic is critical for designing and optimizing the PET plastic extruder screw barrel structures. This knowledge helps customers choose a high-quality PET plastic extruder screw barrels, ensuring efficient and consistent production.
For detailed information on screw parameters and custom screw designs, please contact us or visit our website. Our team of experts is ready to assist you in selecting the perfect screw for your PET extrusion needs.
About HUACHEN Screw
Since 1993, HUACHEN Screw has been a leading manufacturer of PET extrusion screw barrels in Zhoushan Jintang. As one of the best screw barrel manufacturers in China, HUACHEN Screw offers a wide range of services, including drawing rebuilding, design, modification, and customized screw barrels. Our products are trusted globally, known for their quality and performance.
Explore our services and find the perfect screw barrel for your needs:
- – Drawing rebuilding
- – Design and modification
- – Customized screw barrels
Contact the Best Screw Barrel Manufacturer in China
Ready to optimize your PET extrusion process? Contact HUACHEN Screw today for high-quality screw barrels designed for efficiency and durability.
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