Development of rare-earth modified PVC tubes with improved fluorescence and stability

Abstract

This study evaluated the effect of incorporating a rare-earth-based fluorescent powder (REFP) on the mechanical properties and thermal stability of polyvinyl chloride (PVC). A systematic investigation was conducted to determine the optimal loading concentration of fluorescent powder in polyvinyl chloride (PVC) materials, to evaluate its effect on the materials' mechanical properties and thermal stability. A rare-earth-based fluorescent powder (REFP) consisting of Eu³⁺-doped LaP₃O₉ was synthesised using a coprecipitation method. This REFP was then utilised as both a functional filler and a photothermal stabiliser. The REFP was then incorporated into the PVC matrix via thermal processing at various mass concentrations (1%, 2%, 3%, 4%, 5% and 6%). The resulting PVC composites were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectroscopy (FS). Key thermal stability parameters, including thermal stability time, decomposition temperature and volatile content, were also assessed. The findings demonstrated that the inclusion of REFP significantly enhanced the thermal stability of PVC. Specifically, at 3 wt% REFP, the thermal stability time increased by 16%, and the decomposition temperature reached a peak of 158.6 °C. Furthermore, the emission of HCl, a degradation by-product, was effectively suppressed. In addition to the improved thermal properties, the mechanical performance of the PVC fluorescent tubes was also markedly enhanced. At the optimal REFP content of 3 wt%, the elongation at break was 156%, the Vicat softening temperature was 83.6 °C, and the tensile strength was 52.1 MPa. Compared to pristine PVC, these values represent increases of 20%, 4.1 °C and 6.6 MPa, respectively. Overall, incorporating REFP into PVC imparts dual functionality, significantly enhancing the material's mechanical and thermal properties while enabling it to absorb ultraviolet radiation and re-emit it as visible light. This photofunctional PVC composite shows great potential for use in in-situ industrial early warning systems.