In-Process Cure Monitoring of Specialty Material Coatings

We propose to develop and test a prototype TD-THz system and method for the non-contact, rapid, in-process cure monitoring of specialty material coatings. The instrumentation will determine the thickness and cure state both “dry” and “wet” coatings and predict final thickness from “wet” measurements. The system will consist of a rack mounted TD-THz control unit which is connected to a miniature TD-THz reflection sensor via a flexible umbilical mounted onto a robot arm within a paint booth. The fiber optic coupled TD-THz technology is highly suitable, as the sensors are small, light weight, and freely positionable. In-process monitoring is desirable when tight thickness tolerances are required, but difficult, because the coating is uncured. By measuring in-process, the application can be adjusted, and waiting to cure and sanding can be avoided. The TD-THz thickness and cure state measurement offers several advantages: stand-off distances of >30 cm possible; coating thickness from 1000 mils; 100 Hz or greater measurement rate; measurement from conducting and non-conductive surfaces; non-ionizing radiation; no requirement for a reference surface; measurement on wet or dry coating; measurement of thickness of multiple layers; measurement of cure through spectroscopy; and high precision and accuracy.