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PETG Tubing VS Acrylic Tubing Pros + Cons

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post #21 of 387 (permalink) Old 07-12-2014, 03:53 AM
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PETG is not strong. It's more flexible. Acrylic is strong but BRITTLE. Facts, please. Also btw, PETG is modified with glycol.
Malforming is a bad thing in rigid tubing

PETG is not strong? Really? How about some facts then:

PETG : Tensile Strength in PSI = 7,700
Flexular Modules = 310,000

Cast Acrylic: Tensile Strength in PSI = 7,800
Flexular Modules = 350,000

Now, how is it that you claim Acrylic is strong and PETG is not? They are virtually identical in tensile strength and Flexular modules. It seems it is you who fails to provide facts. Where you are correct is that Acrylic is brittle, making it more prone to cracking. Facts, please.

And when you post to correct someone, try not to be so condescending and dismissive.

-Carson

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post #22 of 387 (permalink) Old 07-12-2014, 04:12 AM
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Originally Posted by riesscar View Post

PETG is not strong? Really? How about some facts then:

PETG : Tensile Strength in PSI = 7,700
Flexular Modules = 310,000

Cast Acrylic: Tensile Strength in PSI = 7,800
Flexular Modules = 350,000

Now, how is it that you claim Acrylic is strong and PETG is not? They are virtually identical in tensile strength and Flexular modules. It seems it is you who fails to provide facts. Where you are correct is that Acrylic is brittle, making it more prone to cracking. Facts, please.

And when you post to correct someone, try not to be so condescending and dismissive.

-Carson

How is 310,000 and 350,000 virtually identical It is a difference of about 11%. It's still comparably weaker. Also acrylic is 342000 to 500000 psi tensile strength roughly around 319000 of PETG and their tensile strength is 7000 to 12100
psi vs 7000-8000 of PETG
Also the reason PETG is easier to bend when heated is that they have a low melting/malforming point. That should have been clear
I am being condescending because most of the points you list are all "upsides" when really they aren't. You seem to put PETG in a better light than it truly deserves.

I once lost a system thanks to PETG tubing smile.gif

Another word, isn't PET often stained?
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post #23 of 387 (permalink) Old 07-12-2014, 04:28 AM
 
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Been using petg for a year now. My system is still running and look very clean. I did change the case tho. I bend it all by hand no jig. thumb.gif

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post #24 of 387 (permalink) Old 07-12-2014, 05:16 AM
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Originally Posted by DaveLT View Post


How is 310,000 and 350,000 virtually identical It is a difference of about 11%. It's still comparably weaker. Also acrylic is 342000 to 500000 psi tensile strength roughly around 319000 of PETG and their tensile strength is 7000 to 12100
psi vs 7000-8000 of PETG
Also the reason PETG is easier to bend when heated is that they have a low melting/malforming point. That should have been clear
I am being condescending because most of the points you list are all "upsides" when really they aren't. You seem to put PETG in a better light than it truly deserves.

I once lost a system thanks to PETG tubing smile.gif

Another word, isn't PET often stained?

DaveLT,

 

I don't mean to put PETG in a better light than it deserves.  I was posting my impressions after having worked with it.  I will concede that I may have overstated the strength of the material, when what I meant was its tolerance to stress... and yes, it achieves such tolerance from being more malleable.  I am going to have to contest some of the numbers you just provided, though.

 

You wrote "acrylic is 342000 to 500000 psi tensile strength roughly around 319000 of PETG and their tensile strength is 7000 to 12100".  I am sorry, but that is incorrect.  I think that you meant to write 350,000 to 500,000 tensile modules, not strength.  So if we compare apples to apples and oranges to oranges, we will see a different picture:

 

PETG Tensile Modules (psi) = 320,000

Cast Acrylic Tensile Modules (psi) = 350,000

 

PETG Tensile Strength (psi) = 7,700

Cast Acrylic Tensile Strength (psi) = 8,038 (I understated this earlier... see, no bias;))

 

PETG Flexular Strength (psi) = 11,200

Cast Acrylic Flexular Strength (psi) = 12,000

 

So it is true that PETG is not as strong as cast acrylic, but it is very close... and when I say that, I mean that with respect to using it in watercooling loops.

 

You also write that PETG has a "low" melting/malforming point.  Again, I think that you are using the wrong terminology.  According to the data, PETG has no definite melting point.  It's forming temperature (which is what I think you mean) is 137 C to 160 C.  How is this a "low" malformation point in the context of watercooling?  Are you running boiling water in your system?  I don't think that the cause of the mishap that was linked to earlier (at themodzoo.com) was ever determined... so a low malformation thermal point is not "clear".

 

Regardless of any of this, you had no reason to be condescending.  One of things that I love about pc and tech enthusiasts is that I find them to be altruistic, patient and -- although opinionated -- courteous to each other.  If you feel that I am overstating the positives about PETG, then just say so and rebut my assertions.  I took time to write my post, and I did so simply with the intention of giving my impressions... I am always looking to learn, so I would've been more receptive if you'd posted your second post the first time.  Ya know what I mean.

 

You say that you lost a system to PETG tubing... what happened??? sadsmiley.gif I have all my tubing runs done and have leak tested, but I haven't filled with coolant and cranked up my system.  I think that I'll wait for your response to do so.

 

Lastly, in response to your staining question... no, PETG does not stain.  I do not know about PET, but PETG does not.  If there is one thing that I have read repeatedly with regard to PETG virtues, it is that it has "superior chemical resistance" and is less likely to stain than just about any other transparent plastic -- including acrylic (which is not to say that acrylic will stain either).

 

-Carson


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post #25 of 387 (permalink) Old 07-12-2014, 05:22 AM
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Been using petg for a year now. My system is still running and look very clean. I did change the case tho. I bend it all by hand no jig. thumb.gif

 

Looks GREAT!!!  You did all of the bends without a jig?  Very impressive.  I like your color combo, but your RAM is not quite the same color... you could remove the heatsinks and paint em though :D (I just did this with my Dominator Platinum Light Bar Upgrade heatsink tops).

 

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post #26 of 387 (permalink) Old 07-12-2014, 05:27 AM
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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
I think you've dealt with a poor quality batch of acrylic tubing. I can throw my acrylic tubing at the floor and it won't break, even after repeating several times.

What's the point of stronger tubing when it is surrounded by fragile hardware? Seems so nonsensical to me. Anyone who would allow forces that could destroy acrylic tubing close to their hardware/loop is a barbarian who should not be watercooling his computer.

Acrylic looks best anyways.

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post #27 of 387 (permalink) Old 07-12-2014, 05:40 AM
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[...] Lastly, in response to your staining question... no, PETG does not stain.  I do not know about PET, but PETG does not.  If there is one thing that I have read repeatedly with regard to PETG virtues, it is that it has "superior chemical resistance" and is less likely to stain than just about any other transparent plastic -- including acrylic (which is not to say that acrylic will stain either).

-Carson

I'm not so sure that "superior chemical resistance" has anything to do with staining. I do know that PETG is hygroscopic, meaning that it absorbs water and that water can evaporate through it, similar to flexible tubing. I was under the impression that its being hygroscopic was the characteristic of flexible tubing that related to it's susceptibility to staining.
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post #28 of 387 (permalink) Old 07-12-2014, 05:44 AM
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I think you've dealt with a poor quality batch of acrylic tubing. I can throw my acrylic tubing at the floor and it won't break, even after repeating several times.

What's the point of stronger tubing when it is surrounded by fragile hardware? Seems so nonsensical to me. Anyone who would allow forces that could destroy acrylic tubing close to their hardware/loop is a barbarian who should not be watercooling his computer.

Acrylic looks best anyways.

Hi Hefner,

 

Perhaps the pieces of acrylic that cracked were from a poor batch, as the piece that fractured when it rolled off the table only fell about four feet.  But the resistance to cracking was only one of the virtues that I listed.  I found that PETG was easier to work with: easier to bend without visual anomalies, quicker to heat to bending temp and quicker to cool, more tolerant to reheating in the event of a slight over-bend or under-bend, cuts more cleanly, will bow for insertion into fittings, and it can make tighter bends without collapsing.  In the case of Primochill fittings, I also found that the collars were able to round bends and needed less clearance from the bend in order to make a flush connection.

 

I didn't claim that its being strong is the only reason I liked it.  Did you really read the post that you quoted?  The comment "Anyone who would allow forces that could destroy acrylic close to their hardware/loop is a barbarian who should not be watercooling his computer" is a strange attack at no one.  I never said that I would be implementing any "force" that would crack acrylic... I said that I liked working with PETG for all of the reasons I mentioned.

 

I agree that acrylic is a better looking material due to it having a more glass-like transparency... and I stated this in my post.  As I also mentioned, I would wager that you could not tell the difference if I posted a picture of acrylic and PETG tubing side-by-side from a few feet away.

 

-Carson 


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post #29 of 387 (permalink) Old 07-12-2014, 05:44 AM
 
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Looks GREAT!!!  You did all of the bends without a jig?  Very impressive.  I like your color combo, but your RAM is not quite the same color... you could remove the heatsinks and paint em though biggrin.gif  (I just did this with my Dominator Platinum Light Bar Upgrade heatsink tops).

-Carson

Thank you, I will paint the ram in the future and get orange led lighting on my raystorm cpu block smile.gif Prolly add some lights on the front outer edge of the case too.
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post #30 of 387 (permalink) Old 07-12-2014, 05:54 AM
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I'm not so sure that "superior chemical resistance" has anything to do with staining. I do know that PETG is hygroscopic, meaning that it absorbs water and that water can evaporate through it, similar to flexible tubing. I was under the impression that its being hygroscopic was the characteristic of flexible tubing that related to it's susceptibility to staining.

I am quoting a seemingly knowledgeable forum member, GTUK, who wrote : 

 

"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."

 

PETG and PET are used to contain dyed liquids regularly, though... as well as dyes.

 

I do not know about what causes flexible tubing to stain, though.  If it is because it is hygroscopic, then I would be interested to know why or if PETG doesn't or does stain.  Perhaps Mayhem would be a good resource for knowledge on this, as I know he does extensive testing to ensure that his liquids and dyes are compatible with different tubing and materials and the like.  I wonder if he has done any PETG testing and could weigh in on this question.

 

-Carson


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