Moisture content estimation of polyethylene resin with terahertz time-domain spectroscopy

The moisture content of polyethylene (PE) resin is an important factor to affect the quality of PE pipes used in water, gas and oil transportation. To take advantage of the high sensitivity for water with terahertz radiation, we employed terahertz time-domain spectroscopy (THz-TDS) technology to study the water content in PE master batches. The refractive indexes of samples with varying water contents were determined for frequencies between 0.5 and 1.0 THz. We found the refractive indexes were different among four samples and the trends remained during the repeating measurements in nine days. Those differences in the refractive index might be caused by the water content in PE samples. This method provides a potential nondestructive, fast and contactless process in the analysis of PE moisture content.