PETG - Brittle?

PaulHew

@deckingman Hope you are well.
Beg to differ with 3dfilaprint's own petg. Got 4 rolls of it, 2 not opened.
Very brittle after a print. Box says print @215 - 220 for their PETG, if you check where is comes from, Dutch Filaments, they say 240 +/- 10. Struggled to get it out of the nozzle even and 220, warped.
Printed a Prusa headband for Covid @ 245, eventually got a decent print. Testing item as per guide and it shatters, never had PETG shatter before.
On the otherhand, Tech Outlet's PETG printed @ 245 on a 75 bed, item test is fine, no breakage whatsoever.
Tried the Apple Green filament @ 245 and was getting some nasty fumes from it.
Sadly, it is going back as I really liked the colours, price was expensive, especially for their own brand.

This is my experience / opinion, YMMV.
Paul

antlestxp

The polymaker polylite is pretty good stuff along with the polymax. My go to is the fillamentum cpe. That stuff is fantastic but you can't leave it out too long.

DocTrucker

@PaulHew that is interesting. It's 3D Filaprint that I use too. Usually their premium lines. I also ignore what it says on the box for temps. I'm running at around 245 to avoid weak interlayer strength. Essentially I find best results with PLA amd PETG as the printed parts get a bit of a shiny to themselves.

Filamentive's PETG appears more durable, but teo different print surfaces so not a fair comparison really.

I've no problem with £25 ish per kg. I think some of the cheap far east stuff is a gamble I can't be bothered with. Never had any issue with inconsistent filiment diameter or blocked nozzles. Material cost is generally a small fraction of total cost anyway.

deckingman

I think this thread highlights that there can be huge variability with PET-G. Not just between brands, but between batches of the same brand. There is another thread on these forums (I'm on my phone right now so it's hard to find it) where two users are having to print PET-G at PLA temperatures to get any sense out of it. This particular PET-G is from their normal supplier - just a different colour.

deckingman

......or it might be colour related. Do certain brands give problems with certain colours? The PET-G I used from 3dfilaprint was almost exclusively black. Did uses who had problems with PET-G from the same brand also use black or some other colour.? Could this be a combination of brand and pigment?

arhi

@deckingman said in PETG - Brittle?:

Did uses who had problems with PET-G from the same brand also use black or some other colour.? Could this be a combination of brand and pigment?

the "crazy" issues I'm having with white ones are when petg concerned only this single white spool. as for the "black" one, I have experience with many materials (mostly ABS, HIPS, PC) where black required 5-10C more than any other color from same manufacturer to print identically. In some cases black behaves like glow in dark or metal filled or carbon tubes filled or wood filled filament... just like the black "ink" has larger particles than other ones... With PETG from same manufacturer, best comparison is between "deep, dark, non translucent black " and "translucent black". They behave like totally different filaments while both PETG translucent one is much stiffer, less runny, strings very little while darl non translucent/transparent black feels more like hdpe than petg. They also smell differently while printing.

I sometimes have similar experience like with BLACK with WHITE, but those "snow white" ones, they behave identical like BLACK, require few more C, and behave like "filled" filaments. I assume 'cause those snow white ones use some strong pigments to get the whiteness. Never had those issues with regular whites.

I also noticed with ABS, black one is waaaaaaaaay more resistant to UV than any other color. I expected opposite as black one, exposed to sunlight, get much hotter than other ones.

deckingman

@arhi said in PETG - Brittle?:

.............I assume 'cause those snow white ones use some strong pigments to get the whiteness..........

Highly doped perhaps? (Snow white getting too close to one of the 7 dwarves?)

arhi

@deckingman said in PETG - Brittle?:

Highly doped perhaps?

I think it's a different types of additives to the pigments or different pigments, not the ammount of pigment. For e.g. I know that for clothing they will add some "glow in dark" stuff that makes whites brighter under uv and fluo lights (that's why you have to use flash when taking photos of the bride on the wedding even if you have a lot of lux of led light available, as with only led without flash the "white dress" looks gray and does not pop up)

But that's just guess. I'd really love to ask ppl who actually make filament how different they are in making, what do they add to the pellets for each of them but I never seen any of them (filament makers) join in such conversations

DocTrucker

For completeness my materials are snow white from 3DFilaprint and clear rPETG from filamentive. Very difficult to directly compare due to the colour differences.

I don't think temp is an issue here as I aim for the slight sheen on the part, and keep extrusion rates within recomended for the nozzle. In this case below 10mm3/sec for E3D V6 std with standard 0.4mm nozzle.

DocTrucker

If anything the shield printing has just encouraged me to shop around a bit. I don't do colour preference much, but like to stick to a constant colour and supplier. I am liking the finish on the grey filamentive rPLA parts ao may look thatbway in the future.

DocTrucker

Brand new spool and still got issues. Think I will attempt a return unless the purchase was too long ago.

PaulHew

@DocTrucker said in PETG - Brittle?:

Brand new spool and still got issues.
Of what and where from DocTrucker?

PuterPro

@antlestxp said in PETG - Brittle?:

The polymaker polylite is pretty good stuff along with the polymax. My go to is the fillamentum cpe. That stuff is fantastic but you can't leave it out too long.

PC-Max is one of my all time favs, it also doesn't like being left out. I haven't tried Fillamentum CPE, I'll put it on my list to try, thanks! They've changed PC-Max to PolyMax now, FYI.

Daniel

@DocTrucker
PETG and most polyesters are prone to hydrolysis when exposed to heat in presence of water. The ideal moisture content for PETG is below 300 ppm or parts per million (300 mg of water per kilogram of PETG). To make the problem worst, PETG is fairly hygroscopic (It likes to absorb water). Once you remove it from the bag and the dissecants, it will start the absorption process.
The good thing is that the process is reversible. Heating PETG in presence of Desiccants (Silica Gel) at about 70 Celsius (70 x 1.8+32) approx 158F for 10 hs would dry the polymer while preserving its mechanical properties.
However, if the filament was made with wet resin. We could do very little to save it, since the hydrolysis process already occurred before we processed. If you could return it to the manufacturers and get a fresh batch, life can be better.
Good printing

arhi

@Daniel isn't filament going from the nozzle directly into the warm water bath ?! How does that affect the moisture content?

was made with wet resin.

I recently watched some video (trying to figure out what's wrong with this XXL spool of white petg from dasfilament that print at 180C that strings like crazy) about filament making and guy said that the process starts by

put pellets, additives, pigments into the blender and mix and mix and mix
put the mixed content into the dryer and dry for at least 2 hours

and went on about if you don't dry for at least 2 hours the filament will be %$#@^&# quality...

I guess everyone making filament knows this and I doubt anyone is crazy enough not to dry the mixture before using up all the time and energy to convert that into filament.

Daniel

@arhi
That is a very good observation. Filaments are made by melting dry polymer in the extruded and pushing them through a die with the proper diameter and then immersed into a water bath to solidify.
The residence time in the bath is enough to chill the filament but not enough to to raise the internal moisture content above 300 ppm.
It takes time to make the moisture diffuse into the polymer.

arhi

@Daniel sounds interesting, I have no clue about how that part of the work is done, never looked much in to it before this issues with dasfilament white petg, so I started looking at the process and if anyone published recipes but info about it all is super scarce. Apart from few videos and few pictures info there's nothing out there. Easier to find a procedure to make extazy or heroin than to make filament

Anyhows looks like the general course of action for any filament is the same - if something fishy, dry it first

Daniel

@arhi
I am attaching a link to a resin vendor for injection molders and other plastic processes containing a table for water content on different polymers as well as a reference on how to measure that.
https://omnexus.specialchem.com/polymer-properties/properties/water-absorption-24-hours

What filaments are interested in making?

arhi

@Daniel thanks. No wish to make filament. I just wanted to understand what happened to the spool I had issues with ( saga is here https://forum.duet3d.com/topic/16111/6mm-e3dv6-stringing-petg-any-ideas?_=1589127397515 it's a XXL role of dasfilament petg white that behave weird imo)

zapta

@arhi said in PETG - Brittle?:

if something fishy, dry it first

I god a food dehydrator and tried a few time to dry filaments but I can't say I noticed any before/after difference.