Causes and solutions of PET bottle embryo with water marks

PET bottle preforms are widely used in the packaging industry due to their excellent transparency, toughness, and resistance to high temperatures. However, sometimes the preforms may contain watermarks, which may affect the appearance and quality of the final packaging products. In this article, we will explore the causes of watermarks on PET bottle preforms and propose some effective solutions.

Cause 1: Moisture Content in the PET Resin

The presence of moisture in PET resin can lead to watermarks on the preforms. Moisture can affect the molecular structure of the resin and cause irregularities in the surface of the preforms.

Solution 1: Ensure Proper Storage of PET Resin

Proper storage of PET resin can help prevent moisture from affecting the quality of the preforms. It is important to store the resin in a cool and dry place, away from direct sunlight. Also, the bags or containers that hold the resin should be tightly sealed to prevent moisture from entering.

Cause 2: Poor Drying of PET Resin

If the PET resin is not properly dried before being processed into preforms, it can result in watermarks on the preforms. The moisture in the resin can evaporate during the injection process and cause the watermarks.

Solution 2: Ensure Proper Drying of PET Resin

Proper drying of the PET resin is essential to avoid watermarks on the preforms. The drying temperature and time should be carefully controlled to ensure the resin is completely dry before processing. Generally, the drying temperature should be between 160-180°C, and the drying time should be at least 4 hours.

Cause 3: Poor Mold Temperature Control

Inadequate cooling of the mold during the injection process can cause watermarks on the preforms. Uneven cooling can result in variations in the molecular structure of the PET resin, which leads to surface irregularities.

Solution 3: Ensure Proper Mold Temperature Control

Optimizing the cooling system of the mold and controlling the mold temperature can help prevent watermarks on the preforms. The cooling water should be clean and free from impurities, and the water flow rate should be consistent. Also, the mold temperature should be carefully regulated to ensure even cooling.

In conclusion, watermarks on PET bottle preforms can adversely affect the quality of the final packaging products. Therefore, it is essential to understand the causes of watermarks and take steps to prevent them. By ensuring proper storage and drying of PET resin, and controlling the mold temperature during the injection process, watermarks on preforms can be effectively reduced or eliminated, resulting in high-quality packaging products.