Spectroscopic characterization of the stabilising activity of migrating HALS in a pigmented PP/EPR blend

In previous work, the FT-IR maximum of absorption of a low molecular weight HALS containing a sebacate structure was reported to shift from 1738 to 1732 cm⁻¹ during the photo-aging of polypropylene. Previous studies have shown that the reduced mobility of the molecule caused the absorption to shift towards lower frequencies while decreasing its stabilizing activity. This paper presents further results evidencing the loss of activity of the low molecular weight HALS and proposes a novel mechanistic interpretation for the observed spectral shift.