Plastic Container Quality Control

Birefringence can be used to understand and track the quality characteristics of plastic containers, such as cracking in P.E.T. The plastics used in most containers (e.g. consumer beverages, cleaning and cooking liquids, medical vials) are inherently isotropic. This means that the unstressed plastic material does not show birefringence. When these materials are subjected to stresses from extrusion, stretching and injection, blow molding processes, or even post manufacturing damage, the resultant residual stress in the container material shows up as a birefringence.

Using basic techniques such as a crossed polarizer Polariscope, customers can “see” and subjectively evaluate the condition of a container’s stress profile. Of course when trying to develop controls for a process or production line, or even manage the range of a specific material characteristic, subjective evaluations can lead to disagreement, confusion and improper conclusions. Quantitative measurement of birefringence in a container allows R&D, Design Engineers, and Process Engineers to remove the subjective opinion and apply verifiable quality standards to a material or process.

Hinds Instruments developed the Exicor® birefringence measurement product line to quantify the magnitude and orientation of the stress birefringence in materials. The Exicor® technology is very flexible and can be adapted to evaluate complexes for 3D shapes typical of consumer containers.

These same principles can be applied to glass containers as well.

SYSTEMS AVAILABLE:

Exicor® 150AT for the quality control or research laboratory setting

Contact us to see how Hinds Instruments works with our customers to solve complex metrology problems in manufacturing and research settings.