I. About PET sheet
PET sheet is a new type of plastic product recently developed in recent years, so what is the difference between it and our traditional plastic? The production process of this material is complex and is produced by a series of compression polymerization processes using highly accurate machinery.
The plastic we generally see is a translucent substance. Still, the transparency of this material can change in real-time according to its specific requirements. Because of its malleability and plasticity can also be placed in the home or office as a decorative object. Even if it reaches the end of its life, when it needs to be recycled, even combustion will not produce any polluting gas, and for the environment, The harm is minimal.
2. Production process of PET sheet
PET sheet, like other plastics, is closely related to molecular weight. The characteristic viscosity determines the molecular weight. The larger the typical thickness, the better the physical and chemical properties, but the fluidity is poor, making it difficult to mold. The lower the characteristic viscosity, its physical and chemical properties are poor, and the impact strength is lacking. Therefore, the typical thickness of the PET transparent sheet should be 0.8DL/g-0.9DL/g.
PET sheet extrusion line is crystallization tower, drying tower, extruder, machine head, three-roll calendar, and coiler. The production process is raw material crystallization – drying – extrusion plasticization – extrusion molding – calendering – and winding products.
1) Crystallization: PET sheet Extrusion Line heats and crystallizes PET slices in the crystallization column so that the molecules are arranged neatly. Then, the vitrification temperature of the slices is raised; the purpose is to prevent adhesion during drying and clogging the hopper.
2) Drying: Since water can hydrolyze and degrade PET under high-temperature conditions, resulting in a decrease in its characteristic adhesion, its physical properties, especially impact strength, will decrease with the reduction of molecular weight. Therefore, PET sheet extrusion lines must dry PET before melting and extrusion to reduce moisture content. The drying adopts a dehumidifying dryer, and the hot air passes through a closed-loop into the drying hopper for continuous drying.
3) For extrusion molding: PET is transformed into a polymer with an obvious melting point after crystallization and drying. The molding temperature of the polymer is high, and the temperature control range is narrow. Unmelted pellets and melts are separated by a barrier screw dedicated to polyester, which helps maintain longer shear cycles and increase extruder output.
4) Cooling shaping: melt from the hea1. d directly into the three-roll calender for calender and cooling, three-roll calendar component upper, middle and lower three rollers, the central roller axis is fixed, through the axis up and down movement to adjust the roller gap, the three rollers should ensure the speed synchronization, the speed should be above the extrusion amount speed, the purpose of which is to offset the expansion and weaken the internal stress of the sheet when the material leaves the mold, This makes wrinkles disappear.
5) Traction and winding: the sheet comes out through the calender roller, and the gu1. ide roller enters the traction device. The traction device consists of an active rubber roller and a passive rubber roller. The pneumatic pressure presses the two rolls mainly to prevent the sheet from flattening at the calender roller during the two-roller traction to the coiling device.
3. Innovation points of PET sheet Extrusion Line
1. Twin-screw combination technology
Jwell’s years of PET sheet extrusion line twin screw configuration development and design experience are optimized and combined with advanced software technology. The special double-head threaded components and unique screw combination realize various functions such as conveying plasticizing, mixing, shear dispersion, homogenization, exhaust release, extrusion, and extrusion. In particular, it has high efficiency in removing crystalline water inside PET materials. The specially designed exhaust port is free of material, free and smooth, realizes low-temperature extrusion, and avoids thermal degradation of PET.
2. Vacuum exhaust technology
Multi-stage forced exhaust is efficient and safe to ensure that PET materials are not hydrolyzed, and no crystal points are generated during melting and plasticizing. The special three-stage vacuum exhaust technology and oil and gas separation technology greatly reduce the viscosity reduction of PET with a large pumping capacity and ultra-high vacuum.
3. High-strength roller inner spiral flow technology
PET sheet extrusion line high-strength roller internal spiral flow channel structure design, supporting water temperature control system, make the roller have accurate temperature control and efficient heat transfer effect.
4. Craftsman spirit of the equipment manufacturing process
JWELL comprehensively examines the industrial design of PET sheet extrusion line parts selection, manufacturing technology, machining accuracy, heat treatment and surface treatment, appearance design, etc., to ensure the stability and reliability of the equipment and improve the gear.
4. The performance of PET sheet Extrusion Line equipment is as follows
- Multi-component feeding device technology is suitable for controlling the proportion of new material, recycled material, color masterbatch, etc.
- Crystallization-free drying technology of raw materials, the low overall energy consumption of the unit, saving cost.
- High torque extruder, with torque protector.
- Equipped with a large filtration area melt filter, saving a lot of time and labor consumption for screen-changing operation.
- The three-roll calender roller pressing adopts a hydraulic device, compact structure, convenient arrangement of auxiliary facilities, and simple operation; the water temperature system adopts heating and cooling temperature double PID control technology, etc.
- Online edging, crushing, conveying, and recycling system, special winding structure design, realize online non-stop winding change and unwinding device, saving a lot of working time and labor consumption.
- Online silicon coating system improves sheet adaptability and protection and enhances competitiveness.
- The high-precision twin-screw extrusion system adopts pressure closed-loop feedback control technology, heating and cooling temperature double PID control technology, etc.
- The PET sheet Extrusion Line adopts PLC control to realize automatic power of parameter setting, data calculation, feedback, alarm, and other functions.
- Advanced dual PID control algorithm technology, real-time statistical analysis of technical data, and real-time improvement measures to ensure that the production process is always in a statistical control state to improve the quality, accuracy, energy consumption, and other performance indicators of products.