Meaning
Analytical ratios derived from Fourier-transform infrared spectroscopy absorbance peaks measure the relative intensity of amide I and amide II absorption bands in nylon resin samples to evaluate polymer degradation and composition. The polyamide amide band ratio quantifies thermal oxidation and hydrolysis contamination in molded nylon components. Analytical validity applies to aliphatic polyamides including nylon 6 and nylon 66, stopping where heavy mineral filling or black pigment additives obscure infrared absorption spectra.
Spectroscopic Method
Laboratory technicians scan resin samples using attenuated total reflectance infrared spectroscopy to capture peak height values near 1630 cm-1 and 1535 cm-1. Calculating the polyamide amide band ratio reveals shifts in chemical structure caused by excessive processing heat or moisture exposure. Baseline spectra of virgin resin serve as reference standards.
Degradation Metrics
Thermal exposure during extrusion alters carbon-nitrogen bonds and increases carbonyl absorption peaks relative to amide bands. A lower polyamide amide band ratio correlates with reduced molecular weight and degraded mechanical performance. Material failure analysis relies on this metric to identify regrind overload in injection molded parts.
Pass Threshold
Quality control specifications require batch ratios to remain within five percent of baseline virgin resin metrics. When the polyamide amide band ratio drops below acceptable limits, incoming resin lots face immediate rejection at factory receiving docks.
