PETG - chemically incompatible with glycol?

[Bartacus]

Hey guys,

I thought this deserved it's own thread, as this seems to be a subject not too many people talk about.

A few weeks back, the main man for water cooling in Canada (Daz) posted a short video about PETG. He came across a YouTube video where someone mentioned that PETG was not compatible with glycol based coolants (ie most coolants / additives on the market). So he did some research and found this chemical compatibility chart:

http://sevierlab.vet.cornell.edu/resources/Chemical-Resistance-Chart-Detail.pdf

If you check the PETG column, and scroll down to "ethylene glycol" (page 3 IIRC), there's some scary-sounding info. According to that chart, at 20 degrees Celsius, there's an F footnote, meaning "Some effect after 7 days of constant exposure". At 50 degrees Celsius, the footnote is N, meaning "Immediate damage may occur. Not recommended for continuous use." Now your liquid temperature should never even get NEAR 50C, but this still sounds rather damning.

I'm posting this in the hopes that some experts will chime in here, and provide some clarification, or maybe that some of you (ie TTL) has access to some experts who could shed some light on this. I personally have no experience with PETG (and only just recently began working with acrylic hard tube for the first time).

Discuss!

 

[Cloudraker]

I may be way off base here but ethylene glycol is antifreeze and I was under the impression it wasn't to be used for pc applications. I don't know why you would want to use it anyways. Ethylene glycol is intended to lower the freezing point of water but at the same time it reduces waters capacity for removing heat. That's why you don't run pure antifreeze in vehicles (unless you're in alaska).

 

[JR23]

I don't doubt that PETG is incompatible with some glycol based coolants under certain conditions but personally I don't see how it is advantageous over acrylic anyway other than being cheap.

PETG may have higher impact resistance demonstrated and popularized by the rather irrelevant hammer test however the actual yield strength is very similar for both materials. Having a lower forming temperature is indifferent, acrylic is not difficult to form so I don't really see how that helps. Ultimately acrylic is more stable when exposed to UV light and it's clearer. In addition it's widely available from manufacturers and distributors conscious of aesthetics and quality of finish making it the most suitable material for rigid tubing in my opinion. Nearly all custom loops will contain acrylic already in the reservoir or blocks so coolant compatibility won't be an issue.

I'm not trying to imply that PETG is unsuitable, but I can't personally see a distinct advantage and at present consider acrylic as the optimal material for rigid translucent tubing.

JR

 

[Kilbane]

Ethylene glycol is intended to lower the freezing point of water but at the same time it reduces waters capacity for removing heat. That's why you don't run pure antifreeze in vehicles (unless you're in alaska).

Ethylene Glycol as an Antifreeze is only part of the equation. Yes it can be used to reduce the freezing point of water, it also increases the boiling point. The efficiency over pure H2O to transfer heat is around 50% requiring increased flow within a system to be effective. Heat transport and heat transfer need to be balanced for efficiency. Ethylene Glycol increases heat transport at the cost of heat transfer.
Pure Ethylene Glycol is never run as a pure Antifreeze due to the fact that its freezing point (For crystallisation) is around -12c. By adding a water base to it in turn decreases that freezing point to around -45c when mixed at a 6:4 ratio (why vehicular anti freeze is always a mix of chemicals to dilute rather than pure Ethylene Glycol).

 

[Bartacus]

I may be way off base here but ethylene glycol is antifreeze and I was under the impression it wasn't to be used for pc applications. I don't know why you would want to use it anyways. Ethylene glycol is intended to lower the freezing point of water but at the same time it reduces waters capacity for removing heat. That's why you don't run pure antifreeze in vehicles (unless you're in alaska).

I'm not talking about PURE ethylene glycol, but more glycol based coolants and additives that are sold specifically for PC water cooling use. In my loops I've been using distilled water plus an additive made by Nanoxia called Dazmode Protector. Feser dyes also contain glycol, as does some of Mayhems coolants, which is why I posted this info.

JR23: when Jayz2cents posted that stupid hammer test video, he sold a LOT of newbs on PETG, so I figured this might be relevant to the people. I've only done hard tube once, and recently, using acrylic. Like you, I didn't find it hard to work with at all.

 

[Kilbane]

The issue with EG use in PETG as far as i'm aware is down to heat allowing EG to start to bond. PETG is made of substantial quantities of EG. Ironically Pure EG will not effect PETG. Dependant on the base mixed with EG will ultimately effect the ability of any interactions between the two. EG in coolants used for PC's is generally going to be such a low level that will unlikely have any effect on the PETG.

As far as the whole thing goes, it is more down to "what if's" due to the chemical interactions that "Could" occur. EG has been used in coolants for a long time, as has PETG tubing. As you rightfully said, no loop should be getting to the temperatures required to allow any interactions. But this does not mean it will not happen.

I am with JR23 on the use of acrylic. Yes it can crack, yes it can snap. But the forces required to do this are likely to have already damaged much more sensitive components in any build using it.

 

[Wraith]

JR23: when Jayz2cents posted that stupid hammer test video, he sold a LOT of newbs on PETG, so I figured this might be relevant to the people. I've only done hard tube once, and recently, using acrylic. Like you, I didn't find it hard to work with at all.

As far as using that as a demonstration of Acrylic tubing, you'd have to be a complete moron, no one in their right mind is going to introduce a hammer into their nice new water cooled rigs... that's just silly.

 

[Philhne07]

Ha I don't think I've seen a petg discussion yet that doesn't end up on the hammer ordeal.
I've also been trying to get to the bottom of this chemical resistance of petg. I'm a huge fan of mayhems aurora (been using it for about 4 months) and I know it's 10% glycerol, 90% water. From everything I can gather, there shouldn't be an issue unless I'm reaching otherwise dangerous water temps, which should be avoided with petg anyways. I personally wouldn't want to try running a high glycol concentration but o have yet to hear of a real life issue with petg due to coolant selection, I'd love if someone had some to reference!

 

[B NEGATIVE]

PETG.....lol.

I do not recommend it for many reasons beyond that stupid hammer test that everyone from Jays2pence to L3p seems to think is some sort of validation....

PETG was pushed to market to create a market for Primoschill,no long term testing was done by anyone. PETG is not the same material as used in bottles as so frequently claimed,its sister material PET takes that role.

Its low forming temp has already seen a near catastrophe for one poor Modzoo member, the guys that pushed this product then claim it was 'the superior strength of PETG that saved the day' rather than the low forming temp being the cause.

http://themodzoo.com/forum/index.php/topic/1338-petg-problem/

 

[Bartacus]

Ahhh, I feel instantly validated with B's reply. Daz even said in his video that whoever brought this stuff to market didn't do their homework. Funny how you never heard anything bad about this stuff.

 

[Philhne07]

PETG.....lol.

I do not recommend it for many reasons beyond that stupid hammer test that everyone from Jays2pence to L3p seems to think is some sort of validation....

PETG was pushed to market to create a market for Primoschill,no long term testing was done by anyone. PETG is not the same material as used in bottles as so frequently claimed,its sister material PET takes that role.

Its low forming temp has already seen a near catastrophe for one poor Modzoo member, the guys that pushed this product then claim it was 'the superior strength of PETG that saved the day' rather than the low forming temp being the cause.

http://themodzoo.com/forum/index.php/topic/1338-petg-problem/

didn't that guy discover that his pump wiring was garbage and caused his pump to turn off? I'm not saying petg is great or anything, but that is pretty much the only bad example I've seen around, from looking around to a limited extent. He also said he had to "assist" the tubing into the fittting since it didn't line up well to begin with. Kinda seems like there was plenty of user error in there to make it questionable as to weather it was the petg's fault or not. If this happened more frequently then I'd be more worried but I can't say that I see it as a deal breaker.

 

[Warchild]

Well even if his pump went off from bad wiring, the fact that your everyday joe can suffer with a pump malfunction where it will stop working during a gaming session means this can happen to anyone i suppose?

If you game then you may not even here the pump acting up or not notice the coolant no longer ciculating.

PETG might be good, but when the cost of both PETG and Acrylic is so small, im happy with Acrylic for the time being.