This article will elaborate on the pros and cons of each material and focus on the comparative analysis of Polycarbonate Vs. PETG. To provide you an outline, first I will talk about the details of Polycarbonate followed by PETG and finally compare the two materials.
Polycarbonate (PC) as a 3D printing material
Polycarbonate (PC) is a thermoplastic, lightweight, transparent material made of organic functional groups linked together by carbonate groups. This material is renowned for its incredible strength and durability.
PC is widely used in engineering as well as optical applications, where strength and clarity are desired; for example-mechanical, automotive and electrical components; transparent or translucent screens, etc.
Pros of Polycarbonate
Let’s discuss the advantages of polycarbonate as a 3D printing material:
Superior Strength and Impact Resistance
As already mentioned, polycarbonate is superior to other materials in terms of impact strength. The tensile strength of this material can be around 9000 psi, which is far more than most other plastics, including PETG. Check out this video to see how extraordinarily strong polycarbonate is!
The reason for the strength and toughness of polycarbonate is primarily its bulky repeat units (C15H16O2). Because of this, the polymer chains can hardly slide past each other. As a result, the chains stick together strongly.
Moreover, the length of polymer chains as well as partial crystallinity also contribute to the toughness of the material. Consequently, the material is resistant to impact and fracture, which ensures better safety, and greater performance. Due to the impact resistance, PC is used even in making bulletproof glasses.
In a nutshell, polycarbonate materials can be described as ‘virtually unbreakable’!
Outstanding Heat and Flame Resistance
Polycarbonate has quite high temperature resistance, combined with an inherent flame resistance property. PC also has a high glass transition temperature of 150°C, which means its structural integrity will be maintained up to that temperature. PC is also stable down to -20°C.
On the other hand, its flame-retardant level of UL 94: V-2, hence PC can withstand the flame without significant degradation. Therefore, polycarbonate filaments are great for high-temperature and flame withstanding applications, such as- printing candle or incense holders, lighter/ash cases, functional machine components, etc.
PC can also be designed to block ultraviolet rays and thus it can provide protection from UV Radiations.
Good Chemical Resistance
The chemical resistance of polycarbonate material is pretty good, particularly against diluted acids, alcohols, and aliphatic hydrocarbons. PC is also moderately resistant against oils and greases.
However, PC can be adversely affected by alkalis, aromatic and halogenated hydrocarbons. So you should avoid alkaline cleaners for printed objects made of PC.
Excellent Transparency and Optical Properties
The transparency of polycarbonate is comparable to glass (transmits more than 90% of the light), although the strength of it is almost 200 times higher than glass. Besides, due to having an amorphous structure, PC offers brilliant optical properties, where the refractive index of clear polycarbonate is around 1.58.
Its ability to transmit visible light is superior to most other plastic materials, even PETG. Hence it is an excellent choice as clear plastic, for optical applications such as security screens, boat screens, translucent prototypes, and machine guarding.
Versatility and Bendability
Polycarbonate is a versatile material and can be machine bent without breaking at room temperature. They can also be thermoformed, cut, drilled, and welded as per the requirement of an intended application.
As PC is lightweight, with a density of 1.2 -1.22 g/cm3, there is an immense design possibility if compared to glass. This property also allows for easy installation and transportation of the material.
Besides, polycarbonate also has good electrical insulation properties, which can be used for specific projects.
Ease of Post Processing
As polycarbonate has high impact resistance, it can withstand automated post-processing methods like tumbling quite easily. Moreover, the layered lines and edges can be smoothened by vibrating grit particles, with no damage to the printed component.
Recyclability and Biocompatibility
Polycarbonates are 100% recyclable, which contributes to the sustainable use of this polymer. Some polycarbonate materials can also be manufactured and processed to be biodegradable.
Cons of Polycarbonate
Despite having great benefits, there are also some cons for polycarbonate material, as discussed below-
Effect of Humidity on Polycarbonate
Polycarbonate is a hygroscopic material, which means the material absorbs moisture from the air. This phenomenon may lead to printing defects, such as swelling, bubbles, and inconsistent flow during extrusion. Optical transparency may also get negatively affected by moisture.
Therefore, you should be careful about the storage of PC filament. The material should be stored in a cool, and dry (below 20% humidity) place in order to ensure good printing quality. You can also store the filament in an airtight container with desiccant packets to minimize the exposure to humidity.
In case your PC filament absorbs moisture, you can dry the material in a convection oven before printing.
High Print Temperature with Warping Tendency
Polycarbonate requires a high printing temperature (270°C-310°C) in order to extrude properly. As a result, this thermoplastic polymer is prone to uneven cooling and contraction. These cause internal stress, leading to warping, delaminating, or peeling off the plate. Therefore, maintaining dimensional stability is a challenge.
There are several ways to prevent the problem of warping as well as shrinkage, such as-
- Increasing the ambient temperature
- Slowing down the cooling, and
- Improving the bed adhesion
A heated bed with temperature ranging between 135°C and 150 °C can be a plausible technique to address the solution. This is effective, especially for small size printed objects. As the printed object cannot cool down readily, the chances of warping reduce. All metal hot ends also facilitate consistent extrusion.
Another way is to use an enclosure, where the ambient temperature is maintained close to the glass transition temperature of Polycarbonate material. As PC can generate strong fumes with odors, the enclosure will be useful, particularly if the area is not well-ventilated.
Besides, you can also improve the bed adhesion of the plastic by using different adhesives, such as glue-stick, PEI, or heat-activated liquid adhesive solution during the 3D printing process.
Polycarbonate is Expensive!
As the production of polycarbonate requires high processing temperature, the manufacturing cost is quite high. Hence PC filament can be expensive, while the average price may range from $30 to $93 per kg of the material.
Not Food Safe
The manufacture of polycarbonate involves the use of the chemical bisphenol-A (BPA), which is detrimental to human health. Exposure to BPA can be linked to diabetes and cardiovascular diseases. Thus, PC is not food safe and should not be used in a food container or food packaging applications.
Polyethylene Terephthalate Glycol (PETG) as a 3D Printing Material
PETG is derived from Polyethylene Terephthalate (PET) that is modified with glycol. This alteration with glycol facilitates the machining and 3D printing of the material. Besides, there is enhanced strength, sturdiness, clarity, and usability, compared to regular PET material.
PETG also incorporates a blend of useful properties, which makes it durable like ABS and flexible like PLA. The common applications of PETG are in food containers, mechanical parts, electronics, and phone cases.
Pros of PETG
Now let’s elaborate on the pros that PETG can provide-
Great Strength and Flexibility
PETG comprises 70% of the impact strength compared to Polycarbonate. However, it is much stronger than materials like glass or acrylic. The tensile strength is around 7700 psi.
Due to the excellent strength and impact resistance, PETG is appropriate for stress withstanding applications, for example, mechanical parts, jigs and fixtures, protective components, and prosthetic devices.
Being amorphous in nature, PETG has good flexibility, machinability, and thermoforming characteristics, which allows the material to be hot line bent and welded. PETG can be cut to size for manufacturing commercial products e.g. display units, impact-resistant glazing, factory machine guards, etc.
Convenient Printing Conditions
In general, PETG is not much challenging to print with. If you consider Polycarbonate Vs. PETG materials, the printing temperature for PETG is much less than PC, i.e., 230-250 °C. As PETG is less likely to warp or shrink from temperature fluctuation, the optimum printing conditions are also comparatively reasonable.
Although a heated bed (75°C -90 °C) is recommended, whereas no special hot-end arrangement is necessary. Moreover, PETG does not emit any odorous fume, so an enclosure is not required during printing.
Good Layer and Bed Adhesion
PETG becomes quite sticky during printing, so this material can provide great layer adhesion. For the same reason, it can adhere well to the printing bed, while the chances of warping are negligible.
Aesthetics and Packaging Applicability
PETG has good transparency, so it is used in different product packaging where showcasing the item is desired. Although PETG is inherently clear, it can be easily colored and processed.
It is possible to be molded into different shapes and sizes, or extruded into various designs, including sheets. This thermoplastic polymer can also be hot stamped, or silk screened, which enhances its aesthetic value.
Besides, its ability to endure repeated sterilization also allows its application in medical device packaging as well as in pharmaceuticals. In addition, PETG’s impact resistance property can ensure the safety of the product inside.
Heat and Chemical Resistance
PETG is moderately heat resistant and can withstand temperature for up to 85°C. The chemical resistance of the material highly depends on the temperature, and length of exposure to the chemical. PETG has good chemical resistance against dilute/weak acids, alcohols, and aliphatic hydrocarbons.
However, exposure to strong acid, alkalis, aromatic or halogenated hydrocarbons is not recommended.
PETG is Food-Safe!
As PETG is BPA-free, hence it can be manufactured as food safe. Therefore, PETG is often used in manufacturing as well as in the packaging industry. Some common applications are drinking bottles, food storage containers, cooking oil containers, etc. However, one should always make sure that the material is FDA- compliant.
PETG is more environmentally friendly as it does not release foul odor and harmful fumes. Also, this thermoplastic material is recyclable.
If you compare Polycarbonate Vs. PETG, PETG is much more cost-effective. The average price of the PETG filament may range from $16 to $25 per kg.
Cons of PETG
PETG also has some drawbacks. While some of these are similar to those of polycarbonate material, some are also contrasting.
Similar to Polycarbonate, PETG has the same issue of being hygroscopic, which means the humidity in the air will affect the material performance and printing quality. Consequently, you need to make sure the storage environment is humidity controlled and the material is dry before printing.
Prone to Stringing
Stringing or oozing happens particularly when the extruder in the printer melts excessive material than what is actually needed. This extra molten material drips and sticks to the layer, leading to stringing. As a result, the printing performance is compromised and the outcome deviated from the desired design.
One way to mitigate this problem is to properly adjust the printer settings. If it does not address the problem, using a heat gun to melt and get rid of the strings. Additionally, Slowing down the cooling will also help to prevent the strings from fully bonding to the printed body.
Susceptible to Scratching
PETG has a relatively softer exterior, hence it can be scratched easily. Cracks are much visible in this material and it cannot be polished. Besides, it may be prone to yellowing at the edges upon using inaccurate lasers.
Possibility of Fusing to the Print-bed
As mentioned before, PETG can be super sticky during printing, so this filament may not be suitable for support structures. Moreover, there is a possibility for the material to fuse to the printing bed. This phenomenon may make it difficult to remove the PETG whereas the print-bed surface can get damaged.
In order to avoid this problem from happening, it is recommended to coat the surface with a releasing agent such as glue-stick or hairspray. Contrariwise, using glass or PEI surfaces may not be appropriate for this material.
Polycarbonate Vs. PETG: Comparison of Properties
From the discussion till now, you may already have an idea about the comparative characteristics of Polycarbonate Vs. PETG. Now let’s try to compare their summarized properties side by side to have a better understanding.
So, if you’re hoping to create an incredibly strong and stunning model or piece of work, say a gear in a machine, you will want to print with Polycarbonate due to its strength. But, if you’re hoping to mass produce an everyday item, such as packaging or a small figurine for a board game, PETG should do the job well.
You can always experiment between the two and learn what works best.
Understanding When to Use Polycarbonate Vs. PETG in 3D Printing
I hope this article has helped you to have a holistic insight into Polycarbonate Vs. PETG comparisons from the perspective of 3D printing. While both the materials have some similarities, they are also different in many ways.