PET (Polyethylene terephthalate) preforms, which are the intermediate products used for manufacturing PET bottles, are generally considered to have low hygroscopicity. Hygroscopicity refers to the ability of a material to absorb moisture from its surroundings.
PET itself has relatively low water absorption properties compared to other polymers. However, it is not entirely immune to moisture absorption. Over time, PET can absorb small amounts of moisture from the surrounding environment, especially if exposed to high humidity conditions for extended periods.
The moisture absorption of PET preforms is influenced by various factors such as temperature, relative humidity, exposure duration, and the specific grade or formulation of PET used. Manufacturers typically take precautions to minimize moisture absorption during storage and handling of PET preforms to maintain their quality and properties.
To prevent moisture absorption, PET preforms are often stored in controlled environments with low humidity or in moisture-proof packaging. This helps to maintain the desired properties of the preforms and prevents issues such as dimensional changes, reduced transparency, and degraded performance during subsequent processing steps like injection molding or stretch blow molding.
It's important to note that proper storage and handling practices are crucial to minimize the potential impact of moisture absorption on the quality of PET preforms and the final PET bottles produced from them.