A new system for fast, noncontact, nondestructive measuring thickness of individual layers in barrier bottles and preforms is just now being introduced commercially by TeTechS, Waterloo, Ont. Its PlasThick Multi-Layer Thickness Measurement System reportedly can measure up to 10 layers ranging in thickness from 0.01 to 5 mm in a matter of seconds. It can measure both opaque and translucent containers at speeds of up to five measurement points per second. Thickness measurement accuracy is said to be to 0.01 mm.
The system uses infrared light in the terahertz (1012 Hz) frequency range (1 to 100 micron wavelength), which is located on the electromagnetic spectrum between infrared and millimeter microwave radiation. One of the special properties of this energy band is that it can “see through” opaque and colored materials. The instrument emits a pulse of radiation and measures the “time of flight” for reflections from the interfaces between polymer layers, as well as the inner and outer surfaces of the container. The user interface is a touchscreen-panel with Windows PC software.