Materials of PET bottle

The PET bottle is mainly a pharmaceutical packaging produced by PET as the main raw material, and the PET chemical name polyethylene terephthalate is a thermoplastic material. Generally, the PET monomer is formed by esterification of the present dicarboxylic acid glycol, and then polymerized to form a polymer. These low-viscosity PETs are granulated to form amorphous PET particles, which are then tackified by solids to form bottle-grade PET having an IV of about 0.7-0.86 from low-viscosity PET.

oral liquid bottle 60ml PET

IV is the intrinsic viscosity. The longer the PET chain, the higher the viscosity. The higher the IV value, the better the mechanical properties of PET, the lower the crystallization rate, the better the thermal stability, the better the environmental stress cracking resistance, and the easier the processing. Acetaldehyde is produced, and the so-called AA is the acetaldehyde content.

Intrusion of moisture leads to hydrolysis of PET molecules, molecular chain cleavage, molecular weight reduction, and IV reduction. Affected by the residual catalyst, diethylene glycol content, drying time, drying temperature and extrusion conditions, PET is easily oxidized after being heated, and oxidation causes the PET particles to turn yellow.

During the production of PET bottles, when the temperature is relatively high, PET will degrade to produce acetaldehyde, which will increase the AA value. The amount of acetaldehyde produced is exponentially related to the increase of temperature, which is linear with the heating time. At the same time, the production of acetaldehyde is also related to the amount of catalyst remaining, IV and copolymer.