Detecting PET Preform Defects Under Polarized Light with the PL-P
Updated: Oct 12
Many of the defects found in PET preforms can be seen under polarized light. The PL-P Polarization Light for Preform by AT2E reveals the colored birefringence pattern left by the polymer flow lines during injection molding, so that preform defects can be detected by interpreting these patterns.
How the inspection works
Birefringence pattern: preforms viewed in polarized light show a colored birefringence pattern. It results from the polymer flow lines (molecular orientational strain) produced during injection molding.
Preform at 45° to the polarizing axis: the colored pattern observed is the isochromatic fringe, which indicates the amount of birefringence.
Preform parallel to the polarizing axis: a black isoclinic appears, which indicates the direction of the molecular orientational strain.
Interpretation: by correctly interpreting these flow patterns, many preform defects can be detected.
Product description
The PL-P Polarization Light for Preform (PET preform stress viewer) is used to detect many of the defects found in PET container preforms. Its angle-adjusting design lets operators view the preform at the angle most convenient for them. The upgraded, wider viewing area and sample platform allow more preforms to be placed and viewed at the same time, and leave the operator's hands free.
Key features
Detection of preform defects through the birefringence pattern
45° view: isochromatic fringe, showing the amount of birefringence
Parallel view: black isoclinic, showing the direction of the molecular orientational strain
Angle-adjusting design
Wider viewing area and sample platform: several preforms viewed at the same time
Hands-free viewing
LED light source
Technical specifications
Viewing area: 330 x 150 mm
Overall size: 400 (L) x 302 (W) x 315 (H) mm
Light source: 45 W (LED lights)
Power supply: AC 220 V (AC 110 V optional)
Optional models
Model with a 350 x 350 mm viewing area
APL, with preform support and automatic or manual rotation: preforms rotate freely for 360° viewing, and the multi-position finish support allows several samples to be observed at the same time
APL-24P specifications (other numbers of positions on order): viewing area 380 x 164 mm x 3; overall size 525 (L) x 420 (W) x 850 (H) mm; light source 81 W (LED lights); power supply AC 220 V (AC 110 V optional)
Frequently asked questions
What is the primary function of the PL-P polariscope for preforms?
The PL-P detects defects in PET preforms by viewing them under polarized light, which reveals the colored birefringence pattern produced by the polymer flow lines during injection molding.
How does the PL-P reveal stress in preforms?
With the preform held at 45° to the polarizing axis, the colored pattern observed, the isochromatic fringe, indicates the amount of birefringence. With the preform held parallel to the polarizing axis, a black isoclinic indicates the direction of the molecular orientational strain.
What viewing area and ergonomics does the PL-P offer?
The PL-P offers a 330 x 150 mm viewing area (350 x 350 mm on the optional model). Its angle-adjusting design lets operators view preforms at the most convenient angle, and its wider sample platform holds several preforms at the same time.
What lighting and power specifications does the PL-P use?
The PL-P uses a 45 W LED light source and runs on AC 220 V (AC 110 V optional). Its overall size is 400 x 302 x 315 mm.
Request a quote
AT2E is an ISO 9001 certified company (AFNOR Certification).
Request a quote: info@at2e.com
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