Theoretical and experimental assessment of UV resistance of high‐density polyethylene: Screening and optimization of hindered amine light stabilizers

Abstract

Hindered amine light stabilizers (HALS) are widely used chemical stabilizers for preventing polymer degradation. In this study, the effects of type of HALS and its content in high‐density polyethylene (HDPE) over the stabilization process are investigated employing density functional theory (DFT) and experimental approach. The electrophilicity index of four types of commercial HALS are compared by DFT to select the most effective one. Besides, the HDPE sample containing a phenolic antioxidant and different contents of the selected HALS are experimentally exposed to UV irradiation. The effect of HALS content on the changes in chain microstructure and molecular weight of HDPE are evaluated using gel permeation chromatography and frequency sweep rheometry. In the absence of HALS, HDPE suffers degradation and the phenolic antioxidant causes chain scission. However, by adding HALS, the chain branching and crosslinking mechanisms are predominant. The results of FTIR, DSC, and tensile analyses follow similar trends, revealing that the best stabilization performance corresponds to adding 600 ppm HALS to HDPE.

The UV stability of polyethylene pipes with different comonomer content: Effect of carbon black masterbatch

“…[ 16 ] These functional groups are the oxidative products of Norrish II reaction, which occurs during UV degradation. [ 10 ] As shown, the peak intensity of these functional groups is higher for T100‐N. It can be concluded that the higher comonomer content in polyethylene is associated with the presence of more tertiary carbons and short chains in its chemical structure.…”

“…[7,8] One of the most critical factors affecting PE pipes' mechanical properties and color is the degradation caused by ultraviolet (UV) emitted from the sun. [9,10] The amorphous regions of semi-crystalline polymers are very prone to this degradation. If this happens in PE pipes, efforts to improve the amorphous region through molecular engineering will practically fail, and the product will lose its high performance in sunlight.…”

Oil-Soluble Ultraviolet-Absorbing Carbon Dots Dispersed in Polyethylene Films as Antiaging Materials

“…For S 2p, the peaks at 168.43 and 169.5 eV belonged to the sulfonic group of AOT. 59 1 H and 13 C NMR were also used to characterize the AOT-CDs dissolved in D 2 O. The maximum peak at 4.6 ppm was derived from residual methanol in D 2 O.…”

“…In addition, adding additives is another effective way of making polymers resistant to UV rays, such as UV absorbers, inorganic oxides, and hindered amine light stabilizers (HALSs). Rahimpour et al compared four kinds of HALSs and found that 600 ppm of HALSs could effectively suppress chain scission caused by phenolic antioxidants by scavenging polymer free radicals . Dong et al showed that the poly­(vinyl alcohol) (PVA)/SE film had excellent photostability because the bio-UV absorber SE reacted with radical oxygen as well as reduced oxygen and generated active oxygen species .…”

“…Rahimpour et al compared four kinds of HALSs and found that 600 ppm of HALSs could effectively suppress chain scission caused by phenolic antioxidants by scavenging polymer free radicals. 13 Dong et al showed that the poly(vinyl alcohol) (PVA)/SE film had excellent photostability because the bio-UV absorber SE reacted with radical oxygen as well as reduced oxygen and generated active oxygen species. 14 In addition, many organic UV absorbents are also used to prevent the photooxidation of polymers, including benzophenones, 15,16 Schiff bases, 17 benzotriazoles, 18 and organotin complexes.…”