Novel composite materials with high near-infrared reflectance properties to retard the thermal aging of polyethylene: Pr3+ and Er3+ doped La2Zr2O7 compounds

Abstract

In this paper, Er3+ and Pr3+ successfully replaced La3+ in the lattice without changing the structure of La2Zr2O7 pyrochlore, and finally formed the substituted solid solution La2-xMxZr2O7+δ (M = Er, Pr; x = 0–0.25). SEM analysis shows that the pigments were in the shape of nearly spherical particles with a particle size between 10 and 60 nm. La2-xPrxZr2O7+δ and La2-xErxZr2O7 materials have high NIR reflectance properties, with the NIR reflectance of 68.46%–92.51% and 82.79%–90.89%, which are related to the variation of free carrier concentration due to doping content. Compared with pure polyethylene material, the polyethylene plastic samples containing La2-xPrxZr2O7+δ and La2-xErxZr2O7+δ not only had lower internal surface temperatures, 5.9–11.4 °C and 6.9–13.2 °C lower but also had significantly lower thermal aging. In conclusion, the use of synthetic pigments with high NIR reflectivity as additives can delay the thermal aging of plastics and increase the aging resilience of plastic.