Measuring the Moisture Content of Pulp Injection Molded Products with Terahertz Waves

We proposed to utilize terahertz (THz) waves for the measurement of moisture content of pulp injection molding (PIM) pellets. We developed an automatic and non-destructive THz measurement system with a 0.1 THz source, pyroelectric detector, load cell, and step motor stage. As a first step, the correlation between THz transmittance and moisture content of the PIM product was studied. The results strongly suggest that the proposed method should be applicable to moisture content analysis of PIM products with better than 1% resolution and accuracy, which is much better than the previous studies with more expensive THz sources. Since the contents of pellets and products are the same, it is possible to estimate the moisture content in the pellets by designing similar apparatus. It should be noted that this method is applicable not only to PIM but also has many other applications.