PET sheet
DATE：2021/9/9 8:34:56 / READ： / SOURCE：This station
PET sheet
1. Selection of raw materials and their performance
The raw material of PET sheet is mainly random polyethylene terephthalate (APET).
(1) Intrinsic viscosity The performance of APET is related to the relative molecular mass, and the relative molecular mass is determined by the intrinsic viscosity. The intrinsic viscosity is low, the physical properties of the sheet are poor, and the impact strength is low; the intrinsic viscosity is high, the physical properties of the sheet are improved, the impact strength is large, but the fluidity is poor, the extrusion load is large, and the molding is difficult. Therefore, it is better to produce APET sheet with a polyester resin with an intrinsic viscosity of 0.76-05.
(2) Melting point The melting point of the homopolymer of PET is 263 to 265°C, and the melting point of the PET copolymer varies greatly due to the different content of the auxiliary materials and auxiliary materials copolymerized by the raw material manufacturers. Commonly used copolymerization materials include isophthalic acid (A), cyclohexanedimethanol (CHDM), diethylene glycol (DEG), etc. Generally, copolycondensation polyester resin with a melting point of 242～250℃ is used, which has a low melting point and is convenient for extrusion. Out processing, high crystallization temperature, slow crystallization speed, convenient for secondary molding of APET sheet.
(3) Acetaldehyde content Polyester thermal decomposition will produce acetaldehyde, and acetaldehyde is odorous and toxic, so its content is required to be less than one part per million
(4) Moisture content The moisture content of APET resin directly affects its drying effect, and its moisture content is required to be less than 0.3%.
(5) APET sheet with yellow index is often used as a visual packaging material, and the L value of its yellow index is required to be ≥85 and b value ≤0.5
(6) The content of terminal carboxyl group-COOH content can be used as an index to measure the thermal stability of PET. Generally, the content of terminal carboxyl group is required to be less than 0.03mol/kg. In addition, the thermal stability and crystallization performance should also be considered. PET is easy to heat. Aging reduces the intrinsic viscosity and turns yellow in color. The slower the crystallization speed of the polyresin used for extruding APET sheet, the better.
In summary, the PE991 of Eastman I in the United States is selected for the shaft material of APET extruded sheet. A masterbatch with PET or PEC as the base material is better, and it cannot affect the transparency of the sheet. The dosage is generally 2% ~5%. The selected additives are: anti-adhesive agent PETG67630047; weather release set agent PET9921009 color masterbatch PET921C0; antistatic agent SARMSTAT' G3360.
Author：admin