Preparation and Performance of UV-Resistant Intumescent Flame Retardants for Low Density Polyethylene

Two intumescent flame retardants with UV resistance were specifically designed for low-density polyethylene (LDPE) composites. The mechanical properties, UV resistance, and flame retardancy of these composites were thoroughly evaluated. To delay the premature decomposition of ammonium polyphosphate (APP) under UV radiation, this work employed a coating process using silica gel, melamine formaldehyde resin (MF), and β-cyclodextrin (β-CD) on APP, also known as MCAPP. Furthermore, tris(2-hydroxyethyl) isocyanate (THEIC), which possesses an isocyanate ring, was selected with the purpose of enhancing the absorption of UV radiation and enhancing the fire resistance of LDPE. Finally, the compounds 4-hydroxy-2,2,6,6-tetramethylpiperidine (TMP) and 4-amino-2,2,6,6-tetramethylpiperidine (TEMP), which are hindered amine light stabilizers, were combined with calcium lanceolate (CLS) to create flame-retardant hindered amine light stabilizers (CLS-TMP and CLS-TEMP). CLS-TMP and CLS-TEMP were combined with MCAPP and THEIC to create intumescent flame retardants, which were then incorporated into LDPE to evaluate their flame-retardant properties and UV resistance. The results indicate that the addition of 29.5 wt % (MCAPP/THEIC)/0.5 wt % CLS-TEMP to LDPE increased the limiting oxygen index (LOI) of the composites to 33.2% and achieved a UL-94 vertical flammability rating of V-0. The aging process of the composite samples exhibited a slower progression than that of the control LDPE samples. The sample LDPE/29.5 wt % (MCAPP/THEIC)/0.5 wt % CLS-TEMP showed significant decreases in the rate of shift of both tensile strength and elongation at break. The differences in the LOI before and after the LDPE composites were relatively insignificant after 100 h of UV irradiation.