HDPE Container - Fermentation 1

[sewerratt]

I have HDPE containers (app 12-gal) that used to contain granular calcium hypochlorite (65%). I would like to use it to mix and hold wine ingredients during primary fermentation (app 2 weeks) prior to transfering to a glass secondary fermenter. (I know, technically not a plastics question, but I'm a civil engineer and this forum is the best I could find). Would the HDPE have absorbed any hypochlorite? Any concerns about the hypochlorite leaching out into the mix? I've had them airing out or full of water for several months and no chlorine odor remains.

 

[nbucska]

should be OK.

<nbucska@pcperipherals DOT com> subj: eng-tips

 

[alexit]

From Poly-Flex HDPE liner specs:

Generally polyethylene will be effected by chemicals in one of three ways:

1. No effect—This means that the chemical in question and the polyethylene do not interact. The polyethylene does not gain (lose) weight, swell, and the physical properties are not significantly altered.

2. Oxidizes (cross linking)—Chemicals classed as oxidizing agents will cause the polyethylene molecules to cross link and cause irreversible changes to the physical properties of the liner. Basically it makes the liner brittle.

3. Plasticizes—Chemicals in this classification are soluble in the polyethylene structure. They do not change the structure of the polyethylene itself but will act as a plasticizer. In doing so, the liner will experience weight gain of 3-15%, may swell by up to 10%, and will have measurable changes in physical properties (i.e. the tensile strength at yield may decrease by up to 20%). Even under these conditions the liner will maintain its integrity and will not be breached by liquids, provided the liner has not been subjected to any stress. These effects are reversible once the chemicals are removed and the liner has time to dry out.

Aside from the effect that chemicals have on a liner is the issue of vapor permeation through the liner. Vapor permeation is molecular diffusion of chemicals through the liner. Vapor transmission for a given chemical is dependent primarily on liner type, contact time, chemical solubility, temperature, thickness, and concentration gradient, but not on hydraulic head or pressure. Transmission through the liner can occur in as little as 1-2 days. Normally, a small amount of chemical is transmitted. Generally HDPE has the lowest permeation rate of the liners that are commercially available.

Do this:

Take a freshly-emptied container, fill with distilled or RO water and take a sample of this to a chemical lab (sometimes a local university can do this too), they can meausre the parts per million of the calcium hypochlorite in the (presumably) clean water. Take a cleaned conatiner and do the same thing. If there is no measureable concentration in the cleaned container (or none in the "dirty" container) it is arguably safe to use the container for other purposes.

Of course this would not be acceptable per FDA standards...

 

[rnd2]

I think you can take heart from the fact that HDPE is the material of choice to store calcium hypochlorite. Clearly it would not have been chosen for a chemical corrosive to it or absorbed/dissolved by it.
I brew my own beer in a polyethylene 5 gallon container and sterilise between batches with a recommended sterilizing solution. As far as I can tell it is a powder mixture of alkaline salts and calcium hypochlorite. (Works a treat and the point I'm making is it releases warm dilute chlorine directly against the polyethylene surface.) Mix with warm water and scrub out fermenter. Rinse with clean water until there is no discernable chlorine odour. Start the next batch. This way there is no chance of hung-over yeasts messing with the next brew.