The dispersants effect on physical properties of long-lasting luminescent polypropylene

Two series of blends, O-PP ₁₅ and O-PP ₃₅, were prepared by mixing polypropylene (PP), luminescent powders (SrAl ₂O ₄: Eu ²⁺, Dy ³⁺) of 15 and 35 μm average particle diameter, and hydrophobic dispersant at about 190°C in the Brabender mixer. The effect of amounts and diameter of luminescent powders on the physical properties of PP material were discussed herein. The luminescence and afterglow time tests indicated that the initial luminescence of all blends increased with the luminescent powders amounts. O-PP ₃₅ blends showed lower afterglow luminance than O-PP ₁₅ blends at low luminescent powder amounts. The melting and crystallization temperatures of the blends appeared at 152-168°C and 87-103°C, respectively. The blends displayed peaks attributable to a α crystal structure at 2θ = 18°-19°. The β crystal structure was only evident from its characteristic 2θ peak at 15°-16° in the WAXD pattern of the O-PP ₃₅ blends with high luminescent powder amounts. All of the blends had lower tensile strengths. However, the improvement in the luminescent powder distribution was evident from the SEM images after adding hydrophobic dispersant.