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CDS - Chlorine Dioxide Solution: Chlorine dioxide gas put in water
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CDS storage? CLO2 degrading PP caps of reagent glass bottles. 28 Sep 2021 15:26 #71409

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I got these really nice borosilicate reagent bottles with standardized GL45 PP caps on them from eBay. I thought I was set with the ultimate long(er)-term storage container, but after a few weeks I noticed the CDS eating away at the caps (see images). 

I don't want to consume this CDS, as it obviously has reacted with the plastic of the cap. Does anyone know of a better GL45 cap material suitable for CLO2, or what do most you store your CDS in?

The borosilicate bottles are really nice, but the caps kind of ruined the setup :(

 
 

 
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CDS storage? CLO2 degrading PP caps of reagent glass bottles. 28 Sep 2021 17:41 #71414

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Ah crap, I just spent a boat load of cash on Amber Schott Bottles with Blue Screw GL45 Caps....

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CDS storage? CLO2 degrading PP caps of reagent glass bottles. 28 Sep 2021 18:55 #71424

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@stu77000
Isn't it just bleaching the caps? I've seen that on many of my pet bottles but also on other caps. The gas is strong. :) But if it bleaches the cap, it's probably making it weaker too. :-/

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CDS storage? CLO2 degrading PP caps of reagent glass bottles. 28 Sep 2021 23:30 #71429

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I just found a chemical resistance guide. Confirms PP is no good.
There must be other cap materials available though. Hmm.


 
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CDS storage? CLO2 degrading PP caps of reagent glass bottles. 29 Sep 2021 01:01 #71431

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I only see CLO2 staining in the photos. It does that to many plastics. When the cap in not in the presence of CLO2 gas, the stain will disappear.

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CDS storage? CLO2 degrading PP caps of reagent glass bottles. 29 Sep 2021 16:28 #71440

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While it's true there was some yellowish staining, after 48 hours I can now clearly see there was also bleaching. See the image below compared to an untouched cap. Bleaching implies a chemical reaction, and this chemical reaction (as far as I know) implies there are new or different compounds formed. 

Maybe this is not a problem, I don't know. But I DO know that when I consume this CDS I get arthritis in my fingers. Doing the same with MMS I don't get this problem. So I am wondering if there is a compound here which is producing inflammation. Mind you, I suffer from MCS (multiple chemical sensitivity). I am extremely hypersensitive to a long list of various things.

So this ..thing...whatever it is, perhaps it produces a reaction in me which is not a problem for others.

Anyway, for me this PP cap is not good enough. Still trying to figure out if there exists better materials. I've emailed a couple of screw cap manufacturers..waiting for their replies.

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CDS storage? CLO2 degrading PP caps of reagent glass bottles. 29 Sep 2021 16:33 #71441

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@casper, perhaps what you can do is put a piece of plastic over the top of the bottle and screw the cap down over that.
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CDS storage? CLO2 degrading PP caps of reagent glass bottles. 30 Sep 2021 00:49 #71463

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@stu77000 Heh. I was just thinking about this! It's a good idea.

In fact I got some replies back now. I also emailed Andreas Kalcker not expecting a reply, but he replied with one line. PET.

Here's the summary of replies I got:

Kalcker: PET
Cap Manufacturer 1: Red GL45 caps with PTFE coated silicone seal
Cap Manufacturer 2: GL45 caps of either PBT or PFA with PTFE coated silicone seal
CLO2 Manufacturer: PETG

PET  
= polyethylene terephtalate. I think this is what most drinking water bottles are made of. Cheap and easily available.

PTFE = synthetic fluoropolymer of tetrafluoroethylene. This is basically TEFLON. I checked its chemical resistance to CLO2 and everyone is reporting it as completely inert. This seems to be the best choice, but TEFLON does not have a good reputation otherwise, so not a huge fan. Most likely safe for this purpose though. Caps are expensive (seeing quotes of $5-8 a piece in packs of 10). 

PETG  = Polyethylene terephthalate glycol. "Commonly known as PETG or PET-G, is a thermoplastic polyester that provides significant chemical resistance, durability, and excellent formability for manufacturing.". Very interesting material. Looks like some water bottles could be made out of this too. 
www.acmeplastics.com/what-is-petg

Summary - poor mans's simple solution:
Get a PET or PETG bottle, cut our a circular piece to cover the mouth of the glass bottle and screw the cap over that.
 
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CDS storage? CLO2 degrading PP caps of reagent glass bottles. 30 Sep 2021 06:00 #71470

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@casper Thanks for the info, much appreciated.
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