(1) PET sheet produces crystalline impurities. The reasons are raw materials and corner materials, PET sheet itself will not produce crystalline point impurities, but in the process of processing due to drying problems and a certain degree of added corner materials caused by poor environment and impurities or inferior raw materials, in the PET sheet molding process can not be removed.

(2) Horizontal lines and water lines (orange patterns). Water streak is because when the material generated by the extruder mold flows into the calender roller, there is no residue between the calender rollers, the material is not full, and the surface of the plate is not as smooth as orange peel. The solution is to have visible residues between the embossing rollers, and the residues rotate evenly. The horizontal line is a process defect of the extrusion method, just like the water wave gate of the rolling method, it is the indentation caused by the difference in speed between the two rollers of the calender roller, and the solution is to ensure that the three-roll calender of the three-roll calender improves the accuracy of the speed control, and the synchronization accuracy is also improved, so as to reduce the horizontal line.

(3) Sheets turn yellow, black spots or impurities, streamline, uneven calendering, etc. The main reason for blistering of the plate is that the particles are not dried well and the water content is zero. More than 005%, indicating that the moisture is not dry enough, it will go deep into the section, form molecular bonds, or remain deep inside the slice. Too low a drying temperature or too short a time will affect the drying effect. If the pieces blister, the drying temperature and time should be adjusted immediately. The main reason for the yellowing of sheets is that the drying temperature is too high or the time is too long, so reduce the drying temperature and reduce the drying time. Another reason why the sheets turn yellow is that the melt temperature is too high and the melt temperature needs to be lowered quickly. The main cause of black spot impurities in the debris is the rupture of the filter or the residual PET decomposition material inside the protruder.

Key points of PET sheet production (1) The primary condition for the production of PET transparent plate is the drying time and hot air dew point control, and the drying effect directly determines the physical and mechanical properties and production of the plate. When drying, pay attention to adjust the drying temperature and time, and the drying temperature and time should not be too high or too low. If the dew point cannot fall, check the condition of the molecular sieve. The aging molecular sieve can not absorb the moisture in the air, can not achieve the purpose of drying and slicing, it is necessary to replace the molecular sieve.

(2) When the melt temperature exceeds 280C, the PET sheet will change color or decompose, so the melt temperature should be adjusted below 280C.

(3) The head mold crack gap determines the flatness and thickness uniformity of the plate. The three-roll temperature plays an important role in the transparency and surface finish of the plate. The PET melt should quickly avoid the fastest crystallization temperature region. The melt temperature drops below the crystallization temperature instantaneously, so the distance of the mold from the embossing roller is particularly important.

The main advantages of PET sheet are exquisite appearance, good gas barrier, good protective properties, good toughness and good scalability. PET sheet does not contain stabilizers or plasticizers, does not contain harmful elements, the price is also very good, so it is deeply loved by consumers, PET sheet can be recycled during production, transportation and use, so PET sheet has a high use value. In the PET sheet production process, according to the requirements of the production process, correctly grasp the drying process and the dew point of the hot air, adjust the gap of the calender roller and the traction speed ratio of the subsequent unit, in order to improve the production quality.