PET (polyethylene terephthalate) is a widely used thermoplastic polymer for various applications, such as packaging, textiles, and engineering. PET has excellent mechanical, thermal, and optical properties, and can be recycled and reused for new products. However, PET is also a hygroscopic material, which means it absorbs moisture from the environment, and this can affect its quality and performance. Moisture in PET can cause hydrolysis, which is a chemical reaction that breaks down the polymer chains and reduces the intrinsic viscosity (IV) of the material. IV is a measure of the molecular weight and the degree of polymerization of PET, and it is an important indicator of the strength, stiffness, and processability of the material. Therefore, it is essential to dry and crystallize PET before extrusion, to remove the moisture and prevent the loss of IV.
Infrared crystal dryer PET Granulation is a novel and innovative technology that uses infrared (IR) light to dry and crystallize PET flakes in one step, before feeding them to the extruder for further processing. IR light is a form of electromagnetic radiation that has a wavelength between 0.7 and 1000 microns, and can be absorbed by PET and water molecules, causing them to vibrate and generate heat. IR light can penetrate into the PET flakes and heat them from the inside, resulting in faster and more efficient drying and crystallization than conventional methods, such as hot-air or vacuum drying.
Infrared crystal dryer PET Granulation has several advantages over traditional drying and crystallization methods, such as:
• Reduced drying and crystallization time: The IR light can dry and crystallize PET flakes in 20 minutes, compared to several hours required by conventional methods.
• Reduced energy consumption: The IR light can dry and crystallize PET flakes with an energy consumption of 0.08 kWh/kg, compared to 0.2 to 0.4 kWh/kg required by conventional methods.
• Reduced moisture content: The IR light can dry and crystallize PET flakes to a final moisture content of less than 50 ppm, compared to 100 to 200 ppm achieved by conventional methods.
• Reduced IV loss: The IR light can dry and crystallize PET flakes with a minimal IV loss of 0.05, compared to 0.1 to 0.2 IV loss caused by conventional methods.
• Increased bulk density: The IR light can increase the bulk density of PET flakes by 10 to 20%, compared to the original density, which improves the feed performance and the output of the extruder.
• Improved product quality: The IR light can dry and crystallize PET flakes without causing yellowing, degradation, or contamination, which enhances the appearance and the properties of the final products.
With these advantages, Infrared crystal dryer PET Granulation can improve the efficiency and the quality of PET extrusion, and can meet the requirements of food-grade applications.
The process of Infrared crystal dryer PET Granulation can be divided into three main steps: feeding, drying and crystallizing, and extruding.
Feeding
The first step of Infrared crystal dryer PET Granulation is feeding. In this step, the PET flakes, which can be virgin or recycled, are fed into the IR dryer by a screw feeder or a hopper. The PET flakes can have an initial moisture content of up to 10,000 to 13,000 ppm, depending on the source and the storage conditions. The feeding rate and accuracy are important factors that affect the drying and crystallization performance and the product quality.
Drying and Crystallizing
The second step of Infrared crystal dryer PET Granulation is drying and crystallizing. In this step, the PET flakes are exposed to IR light inside a rotating drum, which has a spiral channel and paddles on its interior. The IR light is emitted by a stationary bank of IR emitters, which are located in the center of the drum. The IR light has a wavelength of 1 to 2 microns, which is tuned to the absorption spectrum of PET and water, and can penetrate up to 5 mm into the PET flakes. The IR light heats the PET flakes from the inside, causing the water molecules to evaporate and the PET molecules to vibrate and rearrange into a crystalline structure. The water vapor is removed by a stream of ambient air, which flows through the drum and carries the moisture away. The spiral channel and the paddles convey the PET flakes along the axis of the drum, ensuring a uniform and homogeneous exposure to the IR light. The drying and crystallizing process takes about 20 minutes, and results in a final moisture content of less than 50 ppm and a minimal IV loss of 0.05. The drying and crystallizing process also increases the bulk density of the PET flakes by 10 to 20%, and prevents yellowing and degradation of the material.
Extruding
The third and final step of Infrared crystal dryer PET Granulation is extruding. In this step, the dried and crystallized PET flakes are fed to the extruder, which melts, homogenizes, and shapes the material into the desired products, such as pellets, fibers, films, or bottles. The extruder can be a single-screw or a twin-screw type, depending on the product specifications and the additives used. The extruder can also be equipped with a vacuum vent, which can remove any residual moisture or volatiles from the melt. The extruding process is influenced by the screw speed, screw configuration, barrel temperature, die geometry, and melt rheology. The extruding process must be optimized to achieve a smooth and stable extrusion, without defects, such as melt fracture, die swell, or dimensional instability. The extruding process can also be followed by a post-treatment process, such as cooling, cutting, or collecting, depending on the product type and the downstream equipment.
Conclusion
Infrared crystal dryer PET Granulation is a novel and innovative technology that uses IR light to dry and crystallize PET flakes in one step, before feeding them to the extruder for further processing. This technology can improve the efficiency and the quality of PET extrusion, by reducing the drying and crystallization time, the energy consumption, the moisture content, and the IV loss, and by increasing the bulk density and the product quality. This technology can also meet the requirements of food-grade applications, by preserving the IV and preventing the yellowing and degradation of PET. This technology can contribute to the sustainability and the circular economy of PET, by enabling the recycling and reuse of PET for new products.
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Post time: Jan-25-2024