Synergistic Enhancement of Environmental Stress Crack Resistance and Mechanical Properties of HDPE via Reactive Blending‐Induced Disulfide‐Linked Covalent Networks

ABSTRACT Environmental stress cracking resistance (ESCR) remains a critical limitation for high‐density polyethylene (HDPE), as conventional strategies to enhance ESCR often compromise mechanical performance or melt processability. Herein, a dynamic covalent network is constructed in HDPE via reactive melt blending using a disulfide‐containing bismaleimide (DTBMI) crosslinker. Radical activation enables DTBMI to capture HDPE macroradicals, forming a dynamically crosslinked network without sacrificing thermoplastic processability. The introduction of 2 phr DTBMI significantly enhances ESCR, with the failure time (f 50 ) increasing by fourfold compared to neat HDPE, while tensile strength, fracture energy, and strain‐hardening behavior are simultaneously improved. Rheological analysis reveals a pronounced increase in low‐frequency modulus and effective network density, indicating strong constraints on long‐time chain relaxation, whereas high‐frequency viscosity remains comparable to that of neat HDPE, preserving melt flow. Fracture morphology after ESCR testing shows pronounced fibrillation, evidencing enhanced stress redistribution and suppressed chain disentanglement. These results demonstrate that time‐scale‐selective dynamic crosslinking offers an effective strategy to reconcile ESCR, mechanical robustness, and processability in HDPE, providing new insights for the design of durable polyolefin materials.