PET, also known as polyethylene terephthalate, is a high-performance polyester material that is highly favored in many industries, especially in the field of GF-PET (enhanced PET) preform production where customer demand is strong. Given the excellent rheological properties exhibited by PET in the molten state and its sensitivity to pressure being higher than temperature, the joint research mold, as a leader in mold manufacturing, deeply understands and optimizes the relevant production processes, with pressure regulation as the core, accurately improves melt flowability, and ensures excellent preform quality.
1. Fine processing of plastics
Considering the hydrophilic properties of PET materials and their sensitivity to moisture at high temperatures, Heyan Mold pays special attention to the drying treatment of raw materials during the production process. The recommended drying temperature is at least 4 hours at 150 ℃, or preferably 3-4 hours at 170 ℃, to ensure that the moisture content is minimized and avoid discoloration and brittleness of the product caused by a decrease in molecular weight. In addition, Heyan Mold recommends that the proportion of recycled materials used should not exceed 25%, and the recycled materials must be thoroughly dried to ensure the quality of the finished product.
2. Professional selection of injection molding machines
Considering the high melting point and short melt stability time of PET material, Heyan Mold recommends using an advanced injection molding system with rich temperature control sections and less self friction heat generation during plasticization process. Ensuring that the actual weight of the product (including the nozzle material) is not less than 2/3 of the machine injection volume is an important principle summarized in the long-term practice of Heyuan Mold. In order to better serve PET production, Heyan Mold has also developed a specialized plasticizing system for small and medium-sized PET series, and recommends that the clamping force should be greater than 6300t/m ² to meet the efficient and stable production needs.
3. Accurate design of molds and gates
In terms of mold design, Heyan Mold recommends using hot runner molds to form PET preforms, in order to reduce heat loss and improve production efficiency. A heat insulation board with a thickness of about 12mm is installed between the mold and the injection molding machine template, which provides both insulation and pressure resistance. The exhaust system is carefully arranged to ensure sufficient and not excessive exhaust, prevent local overheating or fragmentation, and avoid flash problems caused by deep exhaust ports.
4. Accurate control of melt adhesive temperature
By using the air injection method for measurement, it is recommended to set the melt adhesive temperature between 270-295 ℃ for the joint research mold, and for the enhanced GF-PET, it can be increased to 290-315 ℃. The precise temperature control system ensures uniform melting of materials, laying the foundation for high-quality preforms.
5. Optimization of injection speed and back pressure
Heyan Mold emphasizes that a faster injection speed should be used during PET injection molding to prevent premature solidification of the melt, but also to avoid high shear rates and material breakage caused by excessive speed. At the same time, the back pressure setting should be as low as possible, preferably not exceeding 100 bar, to reduce wear, and usually no back pressure is needed.
6. Strict control of retention time
To prevent a decrease in molecular weight, Heyan Mold reminds operators to control the residence time of the melt in the barrel and avoid prolonged exposure to high temperatures, especially in environments exceeding 300 ℃. If the downtime does not exceed 15 minutes, air injection treatment can be carried out; If it exceeds 15 minutes, use viscosity PE for cleaning and lower the barrel temperature to the PE suitable temperature until it is turned on again.
7. Comprehensive consideration of precautions
In the production process of PET preforms, the use of recycled materials should be strictly controlled to prevent the phenomenon of "bridging" at the cutting point from affecting the plasticizing effect. At the same time, precise control of mold temperature and material temperature is the key to avoiding the occurrence of "white mist" in products and ensuring transparency.
With its profound expertise in mold design and production, Heyan Mold provides solid technical support and solutions for the high-quality production of PET preforms.
Foshan Heyan Precision Mould Technology Co., Ltd.'s main business is preform moulds, bottle blowing moulds, bottle cap moulds and other products. It has a strong engineering, R&D, technology and sales team, advanced processing equipment and rich project experience. If you want to know more or have special needs, please call 13318345050, or add our WhatsApp.
