Long Persistent Luminescent HDPE Composites with Strontium Aluminate and Their Phosphorescence, Thermal, Mechanical, and Rheological Characteristics.

In this work, HDPE/strontium aluminate-based auto glowing composites (SrAl ₂ O ₄ : Eu, Dy (AG ₁ ) and Sr ₄ Al ₁₄ O ₂₅ : Eu, Dy (AG ₂ )) were prepared, and their phosphorescence studies were conducted. In HDPE/AG ₁ composites, the green emission was observed at ~500 nm after the UV excitation at 320 nm. The HDPE/AG ₂ has a blue emission at ~490 nm and, in both cases, the intensity of emission is proportional to the AG ₁ and AG ₂ content. The DSC data show that the total crystallinity of both the composites was decreased but with a more decreasing effect with the bulky AG ₂ filler. The melting and crystallization temperatures were intact, which shows the absence of any chemical modification during high shear and temperature processing. This observation is further supported by the ATR-FTIR studies where no new peaks appeared or disappeared from the HDPE peaks. The tensile strength and modulus of HDPE, HDPE/AG ₁ , and HDPE/AG ₂ composites were improved with the AG ₁ and AG ₂ fillers. The rheological studies show the improvement in the complex viscosity and accordingly the storage modulus of the studied phosphorescent HDPE composites. The SEM images indicate better filler dispersion and filler-matrix adhesion, which improves the mechanical characteristics of the studied HDPE composites. The ageing studies in the glowing composites show that there is a decrease in the intensity of phosphorescence emission on exposure to drastic atmospheric conditions for a longer period and the composites become more brittle.