Why do PET bottle preforms have scratches? What should we pay attention to during injection molding?

PET materials have many advantages and are usually used in packaging. Medical bottles, cosmetic bottles, beverage bottles, etc. that we see in our lives are all made of it. The production process of pet bottle preforms is relatively complicated. If there is an error in any part of the process, various problems may occur, such as cracks, scratches, etc. Today, we will mainly analyze why scratches appear on PET bottles, and then understand what aspects need to be paid attention to during the injection molding process of bottle preforms. If you are interested, you can come in and discuss it together. Maybe the problems you are facing will be solved here.

Reasons for scratches on pet bottles

1. After the PET bottle preform is opened for injection molding, it may be damaged due to a little residual temperature, resulting in scratches.

2. The ready-made PET bottle preforms may also be collided during transportation, which is also one of the reasons for scratches.

3. PET bottle preforms may cause scratches due to the extrusion process during blow molding.

4. When packaging products in PET bottles, if you are not careful, it may cause damage. Like the Coke we often drink, there is a high probability of scratches during packaging.

Precautions for injection molding of PET bottle preforms

1. Before injection molding of PET bottle preforms, the material needs to be dried for three to four hours to prevent the moisture in the PET from exceeding the limit and affecting the quality of the product.

2. The template and mold of the injection molding machine will need to be separated by a heat insulation board. There should be sufficient exhaust during injection molding to prevent the PET bottle preform from cracking.

3. The melt temperature is controlled at 270-295°C. When injecting PET bottle preforms, the air shot method can be used for measurement.

4. When injecting PET bottle preforms, you need to be quick and control the time within four seconds.

5. The back pressure should be lower than 100bar to prevent wear problems during injection molding of PET bottle preforms.

6. The residence time should not be too long. Usually, if the downtime does not exceed 15 minutes, it only needs to be air-blasted. If it exceeds, you can use viscosity PE for cleaning.

That’s it for sharing the analysis of the causes of scratches on PET bottle preforms and the precautions for injection molding. I hope it can help all my friends.

FAQs

1. Why do PET bottle preforms develop scratches?

Scratches on PET bottle preforms can occur due to various reasons, including damage during injection molding, collisions during transportation, and extrusion process during blow molding. Careful handling and preventive measures are essential to minimize the occurrence of scratches.

2. How can scratches be prevented during the injection molding of PET bottle preforms?

To prevent scratches, it's crucial to ensure the PET material is adequately dried before injection molding to avoid moisture-related issues. The template and mold of the injection molding machine should be separated by a heat insulation board, with sufficient exhaust during injection molding. Controlling melt temperature, injection time, and back pressure are key factors in preventing scratches.

3. What is the recommended drying time for PET materials before injection molding?

Before injection molding PET bottle preforms, the material should be dried for three to four hours. This drying process helps eliminate excess moisture, ensuring the quality of the final product and preventing issues like scratches.

4. How is the melt temperature controlled during the injection molding of PET bottle preforms?

The melt temperature during the injection molding of PET bottle preforms should be controlled within the range of 270-295°C. Air shot methods can be employed for measurement, providing a reliable way to ensure the proper temperature for the injection molding process.

5. What are the recommended measures for controlling residence time during injection molding?

To control residence time, it's advised to keep downtime within 15 minutes. If downtime exceeds this limit, viscosity PE can be used for cleaning. Proper management of residence time prevents issues and helps maintain the integrity of the PET bottle preforms, reducing the likelihood of scratches.