InGaAs Sensor Selection for Foreign Matter Detection
Select standard InGaAs for cost-effective detection up to 1700 nm, or cooled extended InGaAs to capture 2200 nm polypropylene combination bands cleanly.
O-H Absorption Bands
Chemical Signal
Spectroscopic peaks in the infrared range identify the presence of hydroxyl groups within a textile sample. These o-h absorption bands are prominent in natural fibers like cotton, linen and viscose due to the cellulosic structure of the polymer. The primary signal occurs near 1450 nanometers in the near infrared spectrum and is highly sensitive to the presence of water.
Laboratories use these peaks to determine the moisture content of raw materials before processing.
Moisture Interference
Water molecules contain strong hydroxyl bonds that can mask other chemical signals. In high humidity environments, the o-h absorption bands become broader and more intense, potentially overlapping with signals used to identify finishes or dyes. Spectrometers must be calibrated to account for the ambient moisture absorbed by the fiber.
Accurate readings require the sample to be conditioned at a standard temperature and humidity.
Mercerization Check
Changes in the intensity and shape of the peaks indicate shifts in the crystalline structure of the cellulose. After caustic treatment, the o-h absorption bands shift as the hydrogen bonding within the fiber reorganizes. This provides a non destructive way to verify that the mercerization process has been completed successfully.
Technicians monitor these shifts to ensure consistency across different production lots.
Spectroscopic Accuracy
Precision in locating the center of the peak is necessary for identifying fiber blends. While cotton and wool both show hydroxyl signals, the specific environment of the o-h absorption bands differs based on the molecular surroundings. Modern analytical software uses these differences to calculate the ratio of natural to synthetic fibers in a yarn.