Hand sanitizer: which bottle stands up to alcohol
Hand sanitizer is mostly alcohol: often more than 70%. Such a content forgives no approximation. It passes through some walls, attacks some materials, and ignites at room temperature.
By Tecmom editorial team · 2 min read
What a sanitizer contains
The World Health Organization publishes two reference formulations for hand rubbing. The first contains 80% ethanol, the second 75% isopropyl alcohol, both with a little glycerol, to limit skin drying, and a small dose of hydrogen peroxide. Commercial gels add a thickener, and sometimes a fragrance.
Depending on the country, these products are medicines, biocides or cosmetics. Their bottle faces the same content everywhere.
A material that holds alcohol
High-density polyethylene, polypropylene and PET resist ethanol and isopropanol well at the concentrations used: they neither swell nor dissolve. That is why these three materials dominate the market. Some more fragile clear plastics, on the other hand, can crack in contact with alcohol when they are under stress.
The gel's additives matter too: a fragrance, an oil or a surfactant can behave differently from alcohol alone. See our article on environmental stress cracking.
Alcohol that escapes
A poorly closed bottle lets the alcohol evaporate. The strength drops, and below a certain threshold the product loses its efficacy. The first defence is the closure: flip-top cap, screw cap or pump, each with its own seal.
The wall itself lets a little vapour through over the months, more so when it is thin and storage is warm. Weight monitoring during stability studies measures it; see our article on permeability.
A flammable liquid
The WHO guide gives a flash point of 17.5 °C for the ethanol formulation and 19 °C for the isopropanol one: at room temperature, their vapours can ignite. Storage, transport and labelling therefore follow the rules for flammable liquids.
For the bottle, this means a closure that does not leak lying down, and cases that withstand stacking. The material is chosen with our advice page HDPE, PET, PP.
A hand sanitizer bottle has to do three things at once: resist alcohol, keep it inside, and never let it leak. The last two are the hardest.
Glossary
- Hand sanitizer
- An alcohol-based hand rub, thickened into a gel.
- Alcohol strength
- The proportion of alcohol in the product, by volume.
- Flash point
- The lowest temperature at which a liquid's vapours can ignite.
- Flip-top cap
- A closure with a hinged lid, moulded in one piece with its hinge.