1 PET structure
PET is an organic polymer compound, is composed of carbon, hydrogen, oxygen three elements. The molecular structure is as follows: H- [OCH2CH2-OOC-CO! -OHPET is generally carried out by direct esterification or esterification of terephthalic acid (PTA) or dimethyl terephthalate (DMT) with ethylene glycol (EG) Exchange reaction to produce PET monomer, and then through the solid phase polymerization and the formation of polyethylene terephthalate. The chemical reaction equation is as follows: HOOC - COOH + 2HOCH2CH2OH "Catalyst base HO - CH2CH2 - OOC - COO - CH2CH2OH + 2H2O
2 PET physical properties
PET according to the polymerization method is divided into homopolymerized and copolymerized PET, according to the use of textile PET, bottle grade PET and sheet grade PET. The physical properties of PET grade are shown in Table 1.
Table 1 Physical properties of PET grade
No. Item Characteristic Value Unit
1 Density 1.4 kg / cm3
2 average molecular weight 25000 ~ 30000
3 IV values 0.70 to 0.85
4 Melting point 250 ~ 260 ℃
5 AA content ≤ 3 mg / kg
6 Moisture ≤0.4%
7-grain-shaped cylindrical or parallelepiped
PET is easy to absorb moisture, need a specific warehouse storage, before processing to be effective drying. In the production of raw materials and injection molding process difficult to deal with the residual amount of PET bottles to release acetaldehyde.
3 biaxially stretched PET bottle performance
(1) has a good light transmittance and gloss, light transmittance greater than 85%;
(2) has good mechanical properties and impact resistance;
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