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PETG Filament | All FAQs Answered

PETG Filament | All FAQs Answered | 3D Printing Spot

Updated by

William Stone

/

April 14, 2021

PETG is a fascinatingmaterial and there is a growing popularity of the material. But withoutsufficient knowledge, the material will only fail to deliver results. We intendto help you by answering the most common FAQ’s surrounding the PETG Filament.

Is PETG stronger than PLA? Is PETGsofter than PLA? Is PETG filament Food Safe? What are its applications? Howmuch does PETG cost? Can you microwave PETG? And many more such questions areanswered in this article.

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Table of contents:

What is PETG Filament?

Polyethyleneterephthalate glycol or PETG is a popular variant of the industrially used PETmaterial. PETG is a copolyester as it combines PET with glycol to significantlyenhance the regular PET material. The addition of glycol improves durability,chemical resistance, and even its formability making it less brittle.

PETG also showcases a betteroverall performance and you can read more about it <Here>.

Popular Characteristics of PETGFilament

·        PETG istranslucent.

·        Temperaturetolerance is higher

·        PETG is anexcellent industrial-grade material.

·        PETG isfunctionally better than ABS and exhibits better reliability than PLA.

·        It is hasa glossy surface finish but is prone to scratches.

·        PETG isalso affected by strong US rays.

Applications of PETG Filament

We take a quick look at some of the popularapplications of the PETG filament

Prototyping

3Dprinting technology was developed as a rapid prototyping tool and so most 3Dprinting materials are used for prototyping. However, their prototypingapplications may differ. PETG filament showcases excellent mechanical andchemical properties.  It has greatdimensional stability and so it is popularly used for functional prototyping orto test products before they are manufactured for scale.

Product Packaging

PETG is acommon product packaging material and so is PETG. Most PETG filaments areFDA-approved and so can be used for applications where they come in contactwith food. They can maintain hygiene standards inside the package and so PETGfilament has a great number of applications in product packaging.

Medical Applications

Beingstrong and chemically resistant, the PETG filament has immense potential in themedical industry. Since PETG can be sterilized the material is even moredesirable to the medical fraternity.

There aremany cases where the material is used for dental applications like braces.

PETG Filament FAQs | Answered

We now take a look atsome of the most popular FAQs about the PETG filament. These answers will helpusers to bust common myths about the material and help in a successful 3Dprinting experience with PETG.

When was PETG Invented?

PETG was firstpatented in 1949 by E. I. du Pont de Nemours and Company but first produced adecade later in 1959 by Kibler C. J. of Eastman Kodak Company. It was, however,commercially produced only in 1977. The initial applications of PETG were inblow-molded products but it was later substituted for PET.

Due to its highclarity, it was desirable but it had issues in colorization. Coloured PETG isvery costly and so it was only after 1993 when a low-cost process was developedthat PETG became acceptable in the market.

How is PETG manufactured?

PETG is a copolyesterof PET made from three components, namely, terephthalic acid (TPA), ethyleneglycol (EG), and cyclohexane dimethanol (CHDM). This oil-based polymer ismanufactured in a two-step, melt-phase polycondensation process. A simpleprocess of combining two monomers.

The firstpolycondensation reaction occurs during the esterification of TPA, EG, andCHDM. After this, the second polycondensation step is carried out at hightemperatures (usually around 280) under high vacuum conditions to form thematerial.

Is PETG safe to breathe?

Unlike ABS whichreleases toxic fumes, PETG does not release toxic fumes when printing.Although, some studies mention small amounts of carbon emissions and so it isalways recommended that PETG is 3D printed properly ventilated room. Preventionis better than cure and so always ensure that you do not breathe any fumes fromany material to avoid the confusion of which fumes are harmful and which arenot.

Is PETG filament Food Safe?

PET is a well-knownfood packaging material with mineral water bottles being one of its widelyknown applications. PETG is simply the addition of glycol to the PET materialand there is no evidence of glycol being toxic. So, it is easy to conclude thatPETG is a non-toxic material that is perfectly safe for food packagingapplications. PETG is considered to be one of the safest 3D printing filamentsout there.

However, it is alwayssafer to get this verified by the filament manufacturer.

Is PETG costlier than PLA?

PETG is a costliermaterial than PLA. PLA is formed from corn starch – a cheaper material whereasPETG is a copolymer that has comes from PET as a base material and thencombined with glycol to form the PETG filament. So the process itself islengthy and involves additional manufacturing costs.

Comparatively, the averagecost of one PLA spool is around $20 while the average cost of one PETG spool isaround $45.

Do you need a heated bed for PETG?

PETG is associatedwith layer adhesion problems. It is often found that users face a tough timeprinting with PETG because the initial layers do not stick to the bed easily.This can be eliminated by using a heated bed. A bed heated around 70oCto 80oC will ensure the first few layers remain warm and they stickto the bed till the entire model is 3D printed.

So, to avoid printfailure, a heated bed is recommended to print with PETG.

Is PETG better than PET for 3DPrinting?

PETG is a copolymer ofPET. This means that though PETG is different from PET, it retains most of thedesirable properties of PET. Especially the ones suited for 3D printing.

Comparatively, PETG islightweight, has better impact and chemical resistance, and is strong yetflexible than PET. PET has higher thermal stability and because of this, itrequires a high printing temperature. This property also leads to layeradhesion issues generally associated with materials like ABS, Nylon, etc.

So, considering allthis, PETG is a better material than PET for 3D printing.

Which is better PETG or ABS?

ABS is a very popular material whereas PETGis rapidly gaining popularity right now. Many believe that PETG is here toreplace ABS, But ABS still holds its place in a critical parameter. We stack upboth these materials to see how to make an informed choice between selectingany one material over the other.

Strength: When stacked up against each other for strength, then PETG has betterstrength than ABS. ABS has an Ultimate Strength of around 40MPa while it ismore than 50MPa for PETG.

UV Resistance: When it comes to outdoor applications, PETG will perform muchbetter than ABS as prolonged exposure to UV rays tend to weaken ABS but has a comparativelylesser effect on PETG.

Emission: It is observed and concluded and widely reported that ABS releasestoxic fumes while printing. These fumes can also cause cancer if inhaled inlarge quantities. A very risky proposition and therefore ABS printing isrecommended to be carried out in a well-ventilated area. PETG on the other handdoes not release toxic fumes, it has low particle emission and is odorless.This is a safe material to print with.

MoistureResistance: Like all thermoplastic polymers,both ABS and PETG are hygroscopic but the choice depends on which material hasa comparatively better moisture resistance. The verdict is PETG. PETG hasbetter moisture resistance so much so that it can be used for applications thatare exposed to moisture or water. ABS cannot be employed for such applications.

TemperatureResistance: On comparing both the materialswe find that ABS has a printing temperature of 210oC whereas PETGhas a printing temperature of 250oC. But this is not a goodindicator of temperature resistance. As explained earlier, the glass transition temperature of ABS (105oC) is higher than that of PETG (85oC). This shows that ifthe 3D printed part requires to sustain a higher temperature then ABS is thebetter material of the two.

Which is better PETG or PLA?

PLA is by far the most popular FDM 3Dprinting material. Almost every single person involved in FDM 3D printing hassome time or the other used this filament. PETG however, is a new entrant or achallenger, so to speak. Both these materials have many differences and it canbe easier to choose between the two materials if a user knows what he expectsfrom the 3D printed part. We compare the two materials based on the mostimportant parameters.

Strength: It is observed that PETG has a higher physical strength than PLA

UV Resistance: PETG exhibits better UV resistance than most FDM 3D printingfilaments including PLA. Therefore it delivers stable performance over timeeven in UV exposed applications.

Biodegradability: PETG is a food-safe and recyclable material but it is not easilybiodegradable. PLA on the other hand is completely biodegradable and if leftout in the open, it will eventually break down.

MoistureResistance: PETG has better moistureresistance than PLA.

Transparency: PETG is already a translucent material and so it is easier toachieve higher transparency in a PETG print than in a PLA print.

What is the effect of heat andmoisture on PETG Filament?

PETG is a stablematerial and not easily affected by external anomalies. However, every materialhas its thresholds and we see how PETG filament holds against the effects of heatand moisture.

Heat: The printing temperature of PETG is around 250oC.This in itself is an indication that the material has better heat resistancethan PLA and ABS. To better understand the effect of heat on PETG, we need tounderstand its glass transition temperature (Tg). The Tg of a material is thetemperature at which the material starts to leave its solid form and becomesviscous liquid or rubbery. This is an indication of how much heat a materialcan successfully sustain before deforming. The glass transition temperature ofPETG is around 85oC while it is around 55oC for PLA.

Moisture: All thermoplastic polymers are hygroscopic andabsorb moisture. PETG filament, however, shows greater resistance to moisturethan filaments like PLA and ABS. So it is not easily affected by moisture/waterand can be used for longer periods in close vicinity of water or high moistureregions.

How to post-process PETG Filament?

All FDM 3D printed parts show visible layerlines on their surface. To improve its appearance many users tend topost-process the part. Since PETG has a high chemical resistance, it cannot bepost-processed by regular methods. We list down some of the common ways topost-process the PETG filament:

Sanding

The most popular method to smoothening 3Dprinted parts is sanding. Sanding is the go-to method as it is easy to perform,cheap as it requires only sandpaper and the finish can be visibly controlled.If dimensions are not critical to a part then sanding is the best method toemploy for post-processing. Although it can become tedious if the art is large,or has tricky curvature and tiny features.

The typical way to sand a 3D printed partis to start with sandpaper with a lower grit and gradually moving towards apaper with a higher grit.

Coating

A contrasting approachto sanding is to coat the 3D printed part. In place of removing materialthrough sanding, we can smooth the surface of the print with a compatiblecoating. A popular coating for PETG filament is epoxy resin.

Epoxy resins are agreat choice because they flow smoothly over the print and do not require brushstrokes. This not only eliminates the effort but also the brush strokes are notseen on the coated surface. Moreover, epoxy provides a glossy surface and thepart gives a shiny glass look to the part.

Users will have tocreate a mixture of epoxy resin as per their choice of epoxy. By adding colors,the coating can enhance the entire aesthetic of the model.

Priming and Painting

Another method similarto coating is priming and painting. This is also a common method that usersemploy to post-processes their 3D printed parts and can be as easily appliedfor PETG filament.

It involves using aprimer as a base coat over the printed part. Users can use a single or a doublelayer of primer on the part. Once the primer is dried and set, the next step isto sand the part so that the brush strokes are sanded off and also excess driedpowder is removed. After this step, the part is ready to be painted. Users caneither use a brush or spray to paint the part. Both methods are efficient andcompletely depend on the choice of the user.

Polishing

While ABS can be easily polished by usingacetone vaporing, PETG cannot be vaporized. Another unique way to post-processPETG filament is by using a polishing compound. The minimum requirement forpolishing a part is to sand the part. Without sanding, the polish won’t stickto the part and it will be a waste of effort.

As explained in sanding, the part should besanded with a low grit paper and then by a high grit paper. Once done, the partshould be polished. Liquid metal polishes like Brasso are very popularpolishing agents for PETG filaments.

Apply the polish by taking a small amounton a soft piece of cloth. Upon careful application, the entire model must bemildly buffed to impart shine to the part.

How to store PETG filament?

It is a well-known fact that allthermoplastic polymers are hygroscopic – which means they absorb moisture fromthe air. Absorbing enough moisture can result in many printing problems likeair pockets in the filament, holes in printed parts, extruder jamming,intermittent gaps in deposition, and others. This results in a failed print.

So to avoid these issues, the PETG filamentshould be securely stored in a dry place. Preferably in an air-tight containerwith silicate bags

About THE AUTHOR

William Stone

William Stone

William has spent 20 plus years in the custom manufacturing industry as a COO, CEO and Owner of various custom product businesses. His experience has exposed him to all types of manufacturing from die cast, die struck, injection molding, CNC machining, laser etching, engraving and of course 3D printing.

Learn more about William Stone

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PETG Filament | All FAQs Answered

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