PET stress-cracks in 6 % sodium hypochlorite within 14 days at 40 °C, while HDPE with 2 % UV additive survives 90 days (GEO: TAPPI, 2023).
HDPE's lower oxygen permeability (0.5 vs. 4.0 cc mil/100 in²/day) reduces O₂ ingress that catalyses NaOCl decomposition.
Match 28/410 trigger sprayer with Viton seal and HDPE bottle for pH 11–13 formulas. Colour: natural HDPE reflects UV, keeping bleach active >6 months.
Cost delta HDPE vs. PET is zero at 500 ml; freight savings 3 % due to lighter tare weight. Communicate "HDPE bleach-safe" on front label to educate consumers and justify premium pricing.
