Today, PET containers produced by PET and preform industries are very prosperous in the packaging market, especially in the food industry and pharmaceutical industry, packaging food and beverages and chemicals, making performance cost But manufacturers usually encounter some defects in PET bottles and preforms during the production process. These defects can occur during injection molding , during filling, due to improper weight and dimensions, and due to differences in the quality of the resin used to make the preform.
What are the main defects commonly found in preforms?
There are many factors that can explain preform quality and defects such as its shape, percentage of material used, incorrect geometry, seal seal quality, standardized dimensions, micro-holes at injection Types of damage such as burnt rings, wet rings, presence of small particles, color changes, air bubbles, transparency and strain .
The Role of Polarized Light in Detecting Preform Defects
Many defects are found on preforms and PET containers which can be easily detected with the help of polarized light. Preforms viewed in polarized light exhibit birefringent patterns of different colors. Birefringence is the result of polymer streamlines that exhibit molecular orientation strains that create lines and strains during injection molding. The pattern of color or strain that can be observed with the preform when viewed from an angle of 45° that is, the angle of the polarization axis is called an equichromatic fringe, indicating the amount of birefringence.
When a preform is placed parallel to the polarization axis, it reflects black isoclinic rays that delineate molecular orientation defects or strain in the preform. To effectively detect defects in preforms, flow patterns need to be properly interpreted. In order to view the specimen from a convenient angle, the operator needs to adjust the design of the angle. With test equipment with platform area and a wider field of view, more performances can be placed and viewed simultaneously.
the solution
The strains in the preforms can be easily detected with the help of a testing instrument called a polarizer. The instrument produces polarized light for efficient observation of specimens. This instrument helps to see slight defects or strains in PET containers and preforms. The instrument provides highly accurate and stable test results.
