Meaning
Non-destructive material analysis techniques measure the light scattered back from a sample surface after illumination with near-infrared radiation. Quality control laboratories utilize near infrared diffuse reflectance to identify the chemical composition and moisture content of incoming polymer pellets. This spectroscopic measurement is confined to the surface layers of the sample and does not probe the deep internal structure of opaque materials.
Spectroscopic Analysis
Light penetrating a short distance into the sample is partially absorbed and scattered back to the instrument detector. The resulting near infrared diffuse reflectance spectrum contains overlapping absorption bands that represent the chemical bonds of the sample. This raw spectral data is processed using chemometric models to extract specific quantitative information about the polymer formulation.
Sampling Advantage
Measurements can be taken directly through transparent plastic packaging without opening the container or preparing the sample. This capability allows for the rapid screening of incoming raw materials at the receiving dock, reducing inspection time from hours to seconds. It also eliminates the need for hazardous chemical solvents that are typically required for traditional wet chemistry analysis methods.
Model Calibration
Mathematical regression models must be calibrated using a set of reference samples with known properties before the instrument can be used for routine testing. The near infrared diffuse reflectance readings must be updated periodically to account for instrument drift and changes in the physical characteristics of the resin pellets. This maintenance ensures that the spectroscopic screening remains accurate and reliable over long periods of industrial use, preventing false rejections that could disrupt the factory’s production schedule.
