A Novel Type II Photoinitiator with Self-Supplied Hydrogen for Anti-Creep Crosslinking Polyethylene Film

Two macromolecular photoinitiators, bis(4-benzoylphenyl) malonate (BPMD) and bis(4-benzoylphenyl) 3,3'-(piperazine-1,4-diyl)bis(3-oxopropanoate) (DBPMD), were successfully synthesized from 4-hydroxybenzophenone (4-BP), malonyl chloride, and anhydrous piperazine. Structural characterization using Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance spectroscopy (¹H NMR) confirmed the expected molecular framework. Ultraviolet (UV) absorption spectroscopy revealed that BPMD and DBPMD exhibited enhanced molar extinction coefficients and red-shifted absorption maxima compared to 4-BP. Migration studies in high-density polyethylene (HDPE) demonstrated significantly lower diffusion rates for BPMD and DBPMD than for 4-BP, with DBPMD exhibiting superior photoinitiation efficiency even in the absence of amine-based activators. Photoinitiation performance, photocrosslinking kinetics, and mechanical evaluations indicated that both BPMD and DBPMD enabled efficient UV-initiated crosslinking, leading to improved tensile strength and creep resistance in polyethylene films. These findings highlight the potential of BPMD and DBPMD as advanced photoinitiators for high-performance UV-crosslinked polyethylene systems.