Keywords
Abstract
High-density polyethylene (HDPE) is among the largest-volume commodity thermo-plastics and one of the most successfully recycled polymers at industrial scale, yet it remains a marginal material in fused filament fabrication (FFF), where crystalliza-tion-induced shrinkage, warpage, weak bed adhesion, and poor interlayer bonding have kept it far behind polylactic acid (PLA) and acrylonitrile–butadiene–styrene (ABS). This review consolidates the experimental literature of roughly the past decade covering the entire chain from resin, or washed post-consumer HDPE waste, to printed part: melt rheology and melt flow index (MFI) requirements, crystallization kinetics, filament ex-trusion practice and quality control, FFF processing windows, bed-adhesion and warpage-mitigation strategies, and the structure–property relationships of printed parts. Reported results demonstrate that, under optimized conditions—nozzle temperatures of approximately 200–240 °C, bed temperatures of 80–110 °C, adhesion aids, and controlled cooling—printed HDPE can approach the tensile performance of injection-molded base-lines, while nucleating agents, natural resins, fibers, mineral and carbon fillers, and polyolefin blending suppress shrinkage and improve stiffness. Recycled HDPE retains a large fraction of its mechanical performance over multiple reprocessing cycles when adequately stabilized, supporting distributed recycling into filament. Remaining bar-riers—recyclate variability, absence of standardized material grades, and limited long-term durability data—are identified together with research priorities for closing HDPE material loops in additive manufacturing.