HDPE Susceptibility to UV Radiation in the Presence of Two‐Dimensional Hexagonal Boron Nitride ( hBN ) and Stabilizer Additives

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ABSTRACT This study examines the photodegradation behavior of nanocomposites composed of high‐density polyethylene (HDPE) and hexagonal boron nitride (hBN) nanosheets, with and without stabilizing additives, under artificial ultraviolet (UV) radiation. The h‐BN bulk was exfoliated via liquid‐phase exfoliation, yielding multilayer nanosheets (6–15 layers) with lateral dimensions primarily between 75 and 200 nm. Ten formulations were prepared in a twin‐screw extruder, which was produced with 5 wt% of h‐BN and 5 wt% of additives: antioxidants (AOX: Irgafos 168 and Irganox 1076), a UV absorber (Tinuvin 326), and a hindered amine light stabilizer (HALS: Tinuvin 622 SF). Next, the planar films were produced in a single screw extruder and exposed to UV radiation in an accelerated aging chamber for up to 4 weeks. Nanocomposites containing HALS exhibited superior UV stability, as evidenced by reduced secondary crystallinity, lower carbonyl group formation, and minimal morphological changes after aging, indicating effective photostabilization and reduced chain scission. Conversely, formulations containing only AOX and a UV absorber exhibited degradation similar to that of pure HDPE, attributed to the consumption of Tinuvin 326. Notably, h‐BN accelerated photodegradation in the absence of HALS, as evidenced by increased carbonyl indices and formation of carboxylic groups, suggesting β‐scission and Norrish type I/II reactions. This catalytic effect may arise from metal impurities in h‐BN or boron oxide formation during aging. HALS effectively suppressed this behavior. The results of this study advance the state of the art in polymer photostabilization by demonstrating that, although there is synergism among photostabilizing additives in HDPE matrices, metallic impurities in hBN play a decisive role in accelerating photodegradation, highlighting the need for rigorous control of nanomaterial purity to develop more efficient and reliable stabilizing systems.

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