Stress in Plastics

The manufacture of plastic parts by its very nature creates stress in the structure. Long polymer molecules that make up the plastics become tangled and aligned along the direction of force during injection molding, extrusion, vacuum forming, or other manufacturing process. With rapid cooling, these long molecules never relax to a normal, random equilibrium position before the plastic part is finished and they become locked in a stressful pattern in the final plastic parts. The anisotropy from the manufacturing processes creates birefringence which can be measured.

Hinds Instruments’ Exicor® birefringence measurement systems are ideally suited to measure birefringence caused by stress in plastics. Our suite of Exicor products includes systems designed to measure a wide variety of sample shapes and sizes from very small millimeter-sized items to very large multiple meter-sized objects.

Plastics often have extremely high birefringence, which is difficult to measure with conventional instruments designed to measure birefringence quantities that are a fraction of the size of the light source. For example, a system using a 633 nm light source can quantitate birefringence up to about 316 nm. Hinds Instruments has recently introduced a unique phase unwrapping technique that allows our birefringence measurement systems to accurately quantitate birefringence up to thousands of nanometers with a 633 nm laser.

For more information about how Hinds Instruments can help you measure stress in plastic parts, please see Residual Stress Birefringence in Optical Materials.


Exicor® Birefringence Measurement Systems



Birefringence Measurement

Contact us for more information on measuring stress in plastics with Exicor systems.