PLA vs ABS: The Main Differences

PLA and ABS are two of the most common 3D printing materials. Learn the differences between PLA vs ABS filaments and how to print them both!

3D printing encompasses many technologies, but the most popular one at the consumer level is fused deposition modeling (FDM). Filaments can be made of different materials but are usually thermoplastics because these can be easily melted and re-solidified.

Of the many different types of filaments, the most popular is polylactic acid (PLA), known for its ease of use and low price. But there are other common materials out there, like acrylonitrile butadiene styrene (ABS), a widely used material for injection-molded consumer products.

PLA and ABS are two of the most popular filaments used for FDM 3D printing. While they’re both thermoplastics and look similar, they have many differences. In this article, we’ll compare the two materials on a few different points, including material properties, printing, and price.

AT A GLANCE

*Note: The HDT values are estimated as per ISO75 @1.8MPa testing standards and can differ depending on manufacturer. Parts will creep significantly under loads at these temperatures or over longer periods of time. Therefore, it’s not recommended to use parts under such conditions for a prolonged period of time.

Material Properties

Let’s first take a look at the material properties of both PLA and ABS. We’ll examine their strength, durability, temperature resistance, post-processability, hydroscopy, and recyclability.

Ultimate Tensile Strength

Ultimate tensile strength (UTS) is the maximum stress that a material can withstand while being stretched or pulled before breaking. It’s measured using a tensile testing machine, which applies a pulling load to a test specimen until it breaks.

According to readily available material datasheets and other tests, PLA has a higher ultimate tensile strength than ABS for the same load specimen printed using the same settings. That said, one should also consider that PLA has a ~20% higher density (~1.25 g/cm3) than ABS (~1.04 g/cm3). This makes their UTS-to-weight ratio quite similar, though PLA still has a slight edge.

How well layers adhere to each other will impact a material’s ultmate tensile strength. Between the two, ABS is more sensitive to layer adhesion issues than PLA. If printed incorrectly (i.e. with insufficient flow and low ambient temperatures), ABS will have lower layer adhesion, which decreases the strength of a part, especially when loading across the layers. However, this won’t be an issue when printing ABS on enclosed printers with high ambient temperatures, as this results in excellent layer adhesion.

Impact Strength

Impact strength, also known as impact resistance, is the ability of a material to withstand shock loading – that is, the ability of a material to absorb a sudden or intense force or shock without breaking. Common test methods include the Izod impact test and the Charpy notched impact test, which strikes a notched specimen using a pendulum and measures energy absorbed during breakage. You can even make a DIY impact testing setup, such as the one used by My Tech Fun.

In terms of impact strength, ABS has a large edge over PLA. This is unsurprising, as ABS is known for its very high impact strength, especially among low-cost polymers. PLA is stiffer and more brittle.

Durability

Describing a material, durability is the ability to last a long time without significant deterioration when subjected to the designed operational conditions. Here, we will just examine UV resistance and chemical resistance.

UV RESISTANCE

While ABS is more UV resistant than PLA, both materials will degrade with UV exposure. You can choose acrylonitrile styrene acrylate (ASA), a slight derivative of ABS, for much better UV and weather resistance. It also maintains the excellent mechanical properties and temperature resistance as ABS but is more expensive than both filaments.

CHEMICAL RESISTANCE

In terms of chemical resistance, PLA is more susceptible to chemical degradation than ABS from a variety of acids and alcohols (and at different concentrations). Prusa Research developed a summary table, where different filaments were tested under laboratory conditions. You’ll see that ABS is rated higher than PLA in most cases.

Temperature Resistance

Temperature resistance is an important aspect to consider for many applications, including machine parts as well as those that will be primarily outdoors. Gradual mechanical deformation can be observed when parts are exposed to high-stress levels for a long period of time. This phenomenon is known as “creep”, and temperature is a major driver of material creep.

The ISO75 testing standard shows the heat deflection temperature, the temperature at which the material deflects by 0.25 mm instantly under small loads of 0.45 MPa and 1.8 MPa. At these temperatures, mechanical properties of the parts are drastically reduced and not fit for mechanical use.

Here, ABS is has a large edge over PLA. While PLA’s heat deflection temperature is around 60 °C, ABS can go until about 100 °C. However, take note that these are not the temperatures at which you can safely use parts in any functional way, especially under loads.

Safe operating temperatures – those with zero or minimal material creep – are much lower than the heat deflection temperature. For example, noticeable creep can be observed on ABS parts in enclosed Vorons when they’re exposed to temperatures above 70 °C over prolonged periods of time.

When it comes to PLA parts, prolonged exposure to temperatures above 35 °C would be problematic. PLA is very intolerant to heat. Given its high creep and very low temperature resistance, the material is unsuitable for any functional parts.

Hygroscopy

Both PLA and ABS are rather hygroscopic, easily absorbing moisture from the air. This moisture deteriorates the material itself, resulting in excessive stringing, air bubbles, and poor layer adhesion during printing. This leads to poor print quality and strength. ABS is generally more hydroscopic that PLA.

In any case, it’s recommended that you store both materials in a non-humid environment and dry them (at about 55 °C for PLA and 75 °C for ABS) prior to printing.

Food Safety

Both pure PLA and pure ABS are non-toxic and food safe. They’re widely used and approved in applications involving food processing and applications. For example, PLA is often used for environmentally friendly cutlery, and ABS for food containers and tools like cookie cutters. However, products for these applications are typically injection molded using pure virgin pellets.

3D printing filaments contain additives that drastically improve the material performance and printing experience – for example, to reduce warping without very high chamber temperatures. Most of the time, these additives make the filament not safe for food. That said, some manufacturers do offer food-grade compliant filaments.

Besides the filaments, there are important hardware considerations related to food safety. The parts of your printer that come into contact with the filament are not likely to be food safe. For example, the extruder gears, the path through the hot end, and nozzle may not be made of a food-grade steel. They might have come into contact with non-food safe filaments or lubricants. Brass nozzles can also wear down, leaving some brass residue in the printed part.

FDM parts can also include small voids between layers where bacteria can grow and take hold. Without appropriate post-processing, these parts are not food safe.

Thus, it’s not recommended to use FDM-printed PLA or ABS parts for food applications, unless you’ve considered and taken steps to prevent any form of contamination.

Recyclability

Recycling-wise, both PETG and ABS are recyclable. However, they both fall under resin identification code #7 (“Other’), which means neither is recyclable in normal collections. Readily recycled materials are from #1 to #6, and they’re the types of plastics that are typically included in street collection recycling programs.

Most of the time, polymers in the #7 category are unprofitable or impractical to recycle, so they’re disposed of instead. That said, there are services that recycle 3D prints, including PLA and ABS materials.

We can also consider biodegradability. PLA is biodegradable and compostable, as it’s made from materials like corn. However, it requires very specific conditions to biodegrade fully, and it will take years or decades to break down substantially in non-industrial composting conditions. Being derived from petroleum, ABS is not biodegradable.

Printing

PLA and ABS are very different materials, as are their printing characteristics. Let’s look at how to print both materials!

Temperature

Temperature is an important parameter to consider when printing both materials.

HOT END

At around 230-270 °C, ABS requires a much higher printing temperature than PLA, which prints at just 190-230 °C. Similar to most filaments, it’s a good idea to lean towards the higher end of this range for better maximum volumetric flow rates and layer adhesion. However, be cautious of exceeding this range significantly, as an overly high temperature may lead to excessive stringing, heat creep, or poor overhangs. As always, remember to refer to the manufacturer’s recommendations!

Although you can print PLA comfortably with a PTFE-lined hot end, it’s still recommended to print both materials with an all-metal hot end for versatility and reliability. With an all-metal hot end, you can print multiple materials on the same printer, and periodic replacements of the PTFE tube is not required.

HEATED BED

A higher heated bed temperature is crucial for printing ABS parts. It not only allows for good first layer adhesion (to reduce warping) but also helps in warming up a passively heated enclosure (which we will discuss next). The temperature should fall in the ballpark of 90 to 120 °C, but experienced users lean towards 110 °C to prolong the life of magnets for popular magnetic build plates.

PLA’s bed temperature range is between 50 to 60 °C. It’s even possible to print PLA without a heated bed or at temperatures lower than 50 °C, but it depends on more factors such as the type of bed surface and whether you’re using adhesives. It might, however, result in warping and other problems, so it’s still recommended to keep to the 50 to 60 °C bed temperature.

Enclosure

An enclosure is not necessary nor recommended for PLA parts. The go-to filament for beginners is much easier to print than ABS. It sticks to a clean build plate well and rarely warps with a bed temperature between the recommended 50-60 °C range. PLA also has great layer adhesion and negligible shrinkage without an enclosure. Therefore, an enclosure is not needed.

However, if you choose to print with an enclosed printer, make sure the chamber temperature doesn’t exceed 40 °C. Given PLA’s very low softening temperature, a high enclosure temperature might result in heat creep and print failure.

When it comes to ABS, an enclosure is crucial for strong and defect-free ABS parts. The material is infamous for its tendency to warp and delaminate across its layers due to thermal contraction.

An enclosure keeps the print enveloped at a warm temperature, resulting in a smaller thermal gradient. Parts are prevented from cooling down too quickly, which alleviates warping and delamination issues. It also reduces temperature fluctuations and drafts, which are detrimental to the material’s printing performance and the strength of printed parts.

A high temperature enclosure or actively heated chamber is best for strong ABS parts. High ambient temperatures allow layers to bond better and relieves internal stresses, resulting in a significantly stronger part. Thus, it’s recommended to have chamber temperatures exceeding 65 °C for strong ABS prints. Even higher temperatures (80-90 °C) are beneficial for strength, but they also demand more cooling.

Cooling

For PLA parts, high cooling is important to prevent defects, overheating, and for good bridging and overhangs. PLA can achieve strong parts and good layer adhesion even with relatively high cooling settings. Thus, you should set cooling for PLA prints towards the high side.

Cooling for ABS is more complicated; it depends on the chamber temperature it’s printed at. Though cooling can improve overhang and bridging performance, excessive cooling or cooling ABS too quickly can result in poor layer adhesion as well as increased warping and delamination. This won’t be a problem for high chamber temperatures, though.

Just keep in mind, the higher your chamber temperature, the more cooling you should use. If your enclosure is a relatively low temperature, passively heated one, the cooling settings should also be on low end.

Post-Processing

Generally, ABS has more post-processibility options than PLA. Users especially like its ability to be vapor smoothed with acetone, creating parts with a very smooth, glossy surface finish similar to injection molded or machined parts.

Also, you can relatively easily modify or glue ABS parts using an effective solvent, such as acetone or ABS glue derivatives. For large parts or modeling, this is especially helpful.

PLA is more difficult to dissolve with solvents, and only specialty chemicals can be used to smooth it. That said, both ABS and PLA can be post-processed easily by sanding, drilling, tapping, and can be painted easily.

Examples

PLA and ABS filaments are the most common materials in hobbyist 3D printing, and of course, there are many brands.