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PETG Tubing VS Acrylic Tubing Pros + Cons

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post #11 of 387 (permalink) Old 05-18-2014, 11:20 PM
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PETG is definitely stronger and is reported to be easier to work with (bends easier) than acrylic. It not being UV resistant like acrylic is though could be an issue I would imagine. Will it yellow or possibly become more brittle over time or who knows what else if exposed to sun or UV lights? Also the fact it is hydroscopic (absorbs water) similar to flexible tubing I suspect could mean it might be more susceptible to staining by dyes/coolants. I don't know the answers to any of those things though as I won't be getting any PETG myself at least not for a while until some of those suggested possibilities of drawbacks from ways it differs from acrylic are confirmed or ruled out.

Is PETG being offered anywhere in any colors like acrylic or just clear?
Define 'stronger'?
Acrylic has much higher tenstile strength than PETG,PETG can be cold bent while acrylic cannot.
Water permeation causes fogging issues as well as fluiid loss,its this permeation that's concerning to me.


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post #12 of 387 (permalink) Old 05-19-2014, 02:37 AM
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Originally Posted by B NEGATIVE View Post

Define 'stronger'?
Acrylic has much higher tenstile strength than PETG,PETG can be cold bent while acrylic cannot.
Water permeation causes fogging issues as well as fluiid loss,its this permeation that's concerning to me.
You can try to define 'stronger' any way you want by any standard, but Bill Owen & Jesse's video showing their "hammer test" shows pretty clearly that PETG tubing is MUCH 'stronger' than acrylic. One small tap on the acrylic and it's shattered. Then a dozen or more harder whacks on the PETG results in nary a scratch.
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post #13 of 387 (permalink) Old 05-19-2014, 03:17 AM
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So impact strength is your only requirement is it?
A test that is not relevant to use is your metric is it?

Sigh.

What about torsional,tenstile and shear strength? The ones that actually matter...

Buy it if you want,I certainly won't.


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post #14 of 387 (permalink) Old 05-19-2014, 04:06 AM
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Originally Posted by B NEGATIVE View Post

Define 'stronger'?
Acrylic has much higher tenstile strength than PETG,PETG can be cold bent while acrylic cannot.
Water permeation causes fogging issues as well as fluiid loss,its this permeation that's concerning to me.
People are definitely too hung up on just shatter resistance, which is quite rare anything will fall on your acrylic unless you decide to hammer your rig. I definitely wouldn't. Of course, this world are made up of fools.
That's true that's why steel cannot be cold bent but Aluminium can. Of course if you bend steel it will succumb to shearing.

That was my point in that fluid loss is the biggest key issue.
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post #15 of 387 (permalink) Old 05-19-2014, 04:23 AM
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Acrylic isn't weak by any means. Acrylic has become quite a popular tubing choice as of late and I have yet to see any problems related to shattering acrylic. And I lurk around buildlogs quite a bit of my time. biggrin.gif

Regardless, I am interested how PETG holds over time. It being easier to bend definitely attracts me but the whole extra strength thing seems really pointless.

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post #16 of 387 (permalink) Old 07-11-2014, 08:33 PM
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Hello all,

I have read through this thread -- as well as those on other forums that discuss this topic -- and I thought I would give my impressions of PETG tubing in comparison to rigid acrylic. I have used only Primochill brand tubing, so it is only this brand for which I can offer insight.

Several people have contested the claim that rigid acrylic is prone to cracking. If you think that it does not crack, you are simply incorrect. I have had two pieces of bent tube that developed hairline cracks... one from accidentally dropping it and the other from causes unknown. Moreover, I had one piece that cracked in half, but this was due to excessive stress caused by my attempting to make a piece fit that was slightly too long. Now, does this mean that rigid acrylic tubing is weak? I guess that depends on how we define weak, so I would not say that. I can say that it is when compared to PETG tubing.

I cannot begin to adequately extoll the virtues of PETG tubing compared to acrylic:

-It is extremely strong and is far more resistant to cracking and scratches. For those who would respond that they haven't had issues with acrylic cracking or scratching, I noticed other virtues of the material.
-It is much easier to work with. It bends more cleanly, and I was able to achieve much cleaner bends (with no variation in diameter along the bend) with far less effort/caution than with rigid acrylic.
-I also found that PETG is capable of sharper bends , requiring a smaller turn radius. Primochill compression fitting collars are easier to slide over PETG tubing and can easily round bends, which means that bends can be made right up to the point of insert -- without needing as much straight tube to line up the compression collar.
-Although PETG is stronger than acrylic, I found it much easier to cut through cleanly, requiring less effort and chipping less.
-PETG tubing is more malleable than rigid acrylic, so if a tube is slightly mis-measured... or if the tubing run was a little off center, it will bow easily, allowing insertion into the fitting. --Lastly, PETG is cheaper -- way way cheaper -- than rigid acrylic. A pack of 4 24" Primochill rigid acrylic tubes costs about 25$, while I purchased a pack of 12 36" Primochill PETG tubing for about the same price (26$ I think).

This is not to say that there aren't any negatives:
-One thing that is noticeable upon close inspection is that PETG tubing does not have the same glass-like transparency that rigid acrylic does . It is difficult for me to articulate the difference in transparency, but I'll try: the rounded PETG tubing has what looks like small lines running down the tubes, which refract light. It's almost as though the tube is made round by making thousands of bends until it appears round (I know that this is not the case, I'm simply trying to describe the way it looks). This is only noticeable upon very close inspection, though, and I would wager that from a few feet away or in a picture, one could not tell the difference between clear acrylic and PETG.
-B Negative reports water permeation as a drawback, so I did a little research. Syan43806 writes:

""PETG" is just another name for PET or Polyethylene Terephthalate. It's literally the same plastic that is found in your soda bottles.

I work in the polymer industry and we manufacturer PET. Overall, this is very interesting but there is ONE concern I do have with PET vs Acrylic and that's the diffusion rate of water in PET vs Acrylic. I don't know about how water acts in acrylic but water can diffuse through PET. For example, a 1 year old soda bottle will look squished because it's lost a lot of water."

This supports B Negatives concern; however, in the same thread GTUK responds

"The water vapour transmission rate of both PET and PETG are similar, but when the PET is stretched or orientated under the correct conditions, the transmission rate can be reduced by about one third. The tube extrusion process does not introduce any orientation into PET."

So the degree to which water permeation is a factor will depend on the manufacturing quality, but it does allow some water vapor to escape over time. If it loses the same amount or less than a plastic soda bottle, though, I imagine I'll be doing maintenance on my loop before this becomes a factor.

-The last purported drawback I have read about is that, as opposed to acrylic, PETG is not resistant to staining. I use Mayhem's red dye, so this was a red flag until I read the following, also written by GTUK:

"The chemical and stain resistance of PET and PETG are very good and will certainly out-perform acrylic. In fact, acrylic (PMMA) is very susceptible to chemical attack, especially when stressed. This normally causes stress cracking, even if the part is annealed to reduce any residual stress."

So, it seems that contrary to what some have claimed, PETG is actually more resistant to staining and tolerates dyes and other chemicals better than acrylic.

In conclusion, I will just say that which tubing to use is a matter of personal preference I suppose. To me, the benefits of PETG far outweigh the drawbacks, and it is now my tubing of choice. I hope that this post has provided users with good info on which they should choose.

-Carson

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post #17 of 387 (permalink) Old 07-11-2014, 09:19 PM
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Yeah but there have been reports (one at themodzoo iirc. EDIT: link) of PETG tube melting in the event of a momentary pump failure, something nylon tube nor acrylic is prone to do before a system powers down for a thermal event. Seems PETG has a lower melting point that could lead to a bad situation becoming something catastrophic.

I also would like to know more how PETG holds up over the long term seeing as it is not listed as being UV resistant like Acrylic. What effects, if any, will sunlight or UV case lighting have on it?

BTW, here's a vid B Negative posted in the acrylic pipebending 101 thread that probably belongs here just as well ...
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post #18 of 387 (permalink) Old 07-11-2014, 10:59 PM
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Yeah but there have been reports (one at themodzoo iirc. EDIT: link) of PETG tube melting in the event of a momentary pump failure, something nylon tube nor acrylic is prone to do before a system powers down for a thermal event. Seems PETG has a lower melting point that could lead to a bad situation becoming something catastrophic.

I also would like to know more how PETG holds up over the long term seeing as it is not listed as being UV resistant like Acrylic. What effects, if any, will sunlight or UV case lighting have on it?

BTW, here's a vid B Negative posted in the acrylic pipebending 101 thread that probably belongs here just as well ...

Interesting... and concerning info on the potential for PETG to melt in the event of pump failure. I have a second pump for redundancy, so the likelihood of my coolant temp rising enough to melt it is low. I wonder what the exact melting point is, though. I wonder if running a 24hr stress test would create the potential for tubing melt. As long as the melting point is higher than say 80 degrees C, I'm not concerned, but any lower than that and I think I can no longer give it my blessing.

Regarding the strength of acrylic, I know that it is strong material... just not nearly as strong as PETG smile.gif

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post #19 of 387 (permalink) Old 07-11-2014, 11:10 PM
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Seems that the operating temp range is -40 C to 82 C. Also, if you read the thread that you linked to, it seems that the PETG malformed rather than melted to the point if leaking. It actually prevented a problem... or so say the posters. Either way, I suppose that I'll just have to wait and see. The potential for heat to cause malformations does mean that bowing the tube in order to get it to fit is probably not a good idea, though.

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post #20 of 387 (permalink) Old 07-11-2014, 11:33 PM
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Originally Posted by riesscar View Post

Interesting... and concerning info on the potential for PETG to melt in the event of pump failure. I have a second pump for redundancy, so the likelihood of my coolant temp rising enough to melt it is low. I wonder what the exact melting point is, though. I wonder if running a 24hr stress test would create the potential for tubing melt. As long as the melting point is higher than say 80 degrees C, I'm not concerned, but any lower than that and I think I can no longer give it my blessing.

Regarding the strength of acrylic, I know that it is strong material... just not nearly as strong as PETG smile.gif

-Carson

PETG is not strong. It's more flexible. Acrylic is strong but BRITTLE. Facts, please. Also btw, PETG is modified with glycol.
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Seems that the operating temp range is -40 C to 82 C. Also, if you read the thread that you linked to, it seems that the PETG malformed rather than melted to the point if leaking. It actually prevented a problem... or so say the posters. Either way, I suppose that I'll just have to wait and see. The potential for heat to cause malformations does mean that bowing the tube in order to get it to fit is probably not a good idea, though.

-Carson

Malforming is a bad thing in rigid tubing
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