Polyolefin Resin Grade Verification via Attenuated Total Reflectance Spectroscopy
ATR-FTIR verifies polyolefin grades by measuring specific infrared absorbance ratios to quantify comonomer content, branching density, and copolymer structure.
Fourier Transform Infrared
Meaning
Analytical technique identifies chemical bonds and molecular structures in polymers by measuring the absorption of infrared radiation. Fourier transform infrared provides a chemical fingerprint of a resin by recording how various functional groups vibrate at specific frequencies. It is the primary tool for verifying resin identity and assessing the degree of oxidation in aged or regrind materials.
The resulting spectrum allows a quality lab to confirm the presence of specific additives such as slip agents or UV stabilizers.
Structural Identification
Modern instruments use an interferometer to collect all frequencies simultaneously, which is the defining characteristic of fourier transform infrared. This approach offers high signal-to-noise ratios and fast data acquisition compared to older dispersive methods. It can detect trace amounts of foreign polymers in a blend by identifying the distinct methylene rocking peaks.
Degradation Analysis
Measurement of the carbonyl index via this method tracks the breakdown of polymer chains during processing or environmental exposure. As a polymer degrades, oxygen-containing groups like ketones and carboxylic acids appear in the spectrum. This data assists the moulder in determining if a batch of regrind has undergone too many heat cycles to maintain structural integrity.
Surface Inspection
Attenuated total reflectance allows for the direct testing of solid moulded parts without destructive sampling. The method provides a rapid check for surface contamination or bloom.