The seemingly half-filled adhesive containers are not a result of cutting corners. For one type of adhesive known as anaerobic adhesive, this packaging design is professional and determined by its unique curing mechanism.
Core Working Principle of Anaerobic Adhesive
Curing conditions for anaerobic adhesives: In the absence of oxygen and upon contact with active metal ions, free radical polymerization occurs to turn the liquid adhesive into a solid. Oxygen acts as a natural polymerization inhibitor for anaerobic adhesives. As long as oxygen remains in continuous contact, the adhesive stays liquid and will not cure.
Three Key Reasons for Half-Filled Packaging
- Reserve air space to prevent premature curing inside the bottle An air layer is intentionally reserved inside the bottle to keep oxygen in constant contact with the adhesive and suppress polymerization. If the bottle is filled to the top with no air left, oxygen inside will be gradually depleted. The adhesive will thicken, clump and fail within its packaging.
- Matching design with breathable LDPE bottles Low-density polyethylene (LDPE) is used for packaging. The bottle walls allow slow air permeation to continuously replenish oxygen, ensuring stable shelf life of the full bottle. Metal bottles and glass bottles cannot be used to hold anaerobic adhesives.
- Reserve expansion space to avoid risks during storage and transportation Temperature fluctuations cause thermal expansion and contraction of the adhesive. The reserved cavity prevents pressure buildup inside the bottle, avoiding bottle bulging and adhesive leakage.
Important Reminder
The volume stated on the label (50 ml / 500 ml) refers to the net content of adhesive liquid, while the bottle itself has a larger internal volume, creating the visual impression of being half-full.
Special note: Do not transfer the adhesive into sealed glass bottles or metal cans. Premature curing is highly likely to occur.
