Polylactic acid (PLA) is the most widely used thermoplastic in extrusion 3D printing. If you’ve ever used an FDM 3D printer, chances are you’ve fed a spool of regular PLA filament through it. That’s because PLA is cheap, biodegradable, and melts at a conveniently low printing temperature.

But although PLA has many advantages, standard PLA filament doesn’t perform to a high enough standard for many serious applications. It absorbs lots of moisture from the air, and its low melting point makes it unsuitable for high-temperature applications (in machinery, for instance). It also exhibits brittleness and can shatter when subjected to strong forces.

The limitations of normal PLA mean that users of FDM 3D printers often choose other commodity polymers like ABS (or engineering plastics such as POM or PETG) when they need to make an end-use part or functional prototype. However, there’s another option that retains the benefits of PLA while mitigating some of its flaws.

PLA+ is a family of “enhanced” PLA filaments comparable in price to ordinary PLA but with slightly better material characteristics. But what exactly is it, and is it worth buying over regular PLA filament?

What is PLA+?

Before we can understand what PLA+ is, we need to understand what it isn’t, and we can do this by comparing it to regular PLA.

Polylactic acid (PLA) is a scientific term for a material made from fermented plant starch (such as corn or sugar cane) that is defined by a specific chemical formula.[1] PLA+, on the other hand, is not a scientific term; it is a marketing term used by material developers to identify a PLA filament that has been modified to perform better. The same goes for terms like PLA Plus, PLA Pro, Engineering PLA, Tough PLA, and Enhanced PLA.

In other words, while PLA+ always contains standard PLA as its base, those “plus” elements can be virtually anything: fillers, pigments, nucleating agents, small quantities of other thermoplastics, or other modifiers.

Many PLA filaments contain calcium carbonate-based additives which can alter the mechanical performance of the filament.[2] Examples of PLA-based filaments enhanced with additives include eSun PLA+, which contains 2% calcium carbonate, and Polymaker PolyMAX PLA, which contains acrylic polymers. On the other hand, PLA+ filament doesn’t necessarily need to contain any additives at all. A company’s “PLA+” product might simply be ordinary PLA processed in a special way that results in good performance.

Unfortunately, lots of material developers do not stipulate the exact chemical composition of their PLA+. But this doesn’t mean that PLA+ is just a gimmick: in many cases, PLA+ does indeed outperform PLA in areas such as layer adhesion and toughness — we just can’t always say why.

There are plenty of PLA+ filaments on the market, though manufacturers do not always use the term “PLA+” to refer to their modified PLA formulations. Products in the PLA+ category include:

• eSUN PLA+

• Polymaker PolyMAX PLA

• Duramic 3D PLA Plus

• Overture PLA Professional

• Filamentive Tough PLA

• Jayo PLA+.

Due to its low price on platforms like Amazon, the eSUN filament has become especially popular.

Finally, it is important to draw a distinction between PLA+ (which is a “tweaked” filament composed almost entirely of PLA) and PLA-based composites. Composites also contain extra ingredients — reinforcing chopped fibers, for instance — but typically in larger quantities, sometimes around 50%. Composites are more expensive than PLA+ and often have engineering applications. Examples of PLA composites include 3DXTech’s CarbonX PLA+CF (a composite of Natureworks PLA and premium high-modulus carbon fiber) and Protopasta’s Iron-filled Metal Composite PLA (a composite of PLA and iron).

PLA vs PLA+: What are the differences?

Because some manufacturers don’t tell us exactly what they put in their PLA+ filament, we can’t really say how PLA and PLA+ differ in terms of their content. However, we can compare PLA and PLA+ in terms of material performance and other characteristics.

Even taking into account variations between different brands of PLA+, there are several notable differences in material performance between regular PLA and PLA+. For instance, PLA+ tends to provide better layer adhesion, toughness, and surface quality, but it may be less convenient than PLA due to its higher printing temperature (making it harder to print on non-heated build plates with a low bed temperature). Depending on the brand, PLA+ may also be slightly more expensive than PLA and is generally available in fewer colors.

The main differences between PLA and PLA+ are explained in the following sections, giving an indication of which material is best in certain situations.

Strength and toughness

Despite its low price, normal PLA is a fairly strong 3D printer filament. It is stronger than ABS, for example, although it also has a high level of stiffness and brittleness.

The brittle nature of PLA makes it unsuitable for demanding applications. It has poor impact resistance and tends to shatter into pieces when it breaks, making it a potential safety hazard.

PLA+ is stronger and more rigid than standard PLA, as well as having a higher level of toughness. Chinese filament company eSUN, one of the main filament brands making PLA+, claims its PLA+ is twice as tough as typical PLA filament, while Filamentive says its Tough PLA has an impact resistance of 29.8 kJ/m² (compared to 3.4 kJ/m² for normal PLA).

Flexibility

PLA+ is usually more flexible than standard PLA, with users of PLA+ filament reporting good ductility of printed parts compared to those printed with regular PLA. PLA+ can therefore be seen as occupying a kind of middle ground between PLA and ABS.

One example of a flexible PLA+ is Sunlu PLA+, a cheap and widely available product that has an elongation at break of 45%. Ordinary PLA typically has an elongation at break of just 5–7%, while the figure for ABS ranges between 10–50%.[3]

Temperature resistance

One of the biggest drawbacks of standard PLA filament is its susceptibility to warping and deformation at higher temperatures. Its temperature resistance is very poor compared to other common 3D printing materials like ABS.

Because of this, developers of PLA+ have attempted to tweak the common filament into being more resistant to higher temperatures, allowing FFF 3D printer users to make functional parts designed for use in hot environments.

But a drawback of this higher temperature resistance is a higher required printing temperature. The eSun PLA+ has a suggested print temperature of 205–225 °C, around 15 °C higher than the company recommends for standard PLA.

Ease of printing

Ease of printing is closely related to temperature resistance, and PLA+ can be regarded as harder to print than PLA if using a beginner-level FDM printer that doesn’t perform well at the slightly higher temperature required.

The difficulty with PLA+ is compounded if a 3D printer does not have a heated print bed/build plate. Print bed adhesion (first layer adhesion) is typically worse with PLA+ than standard PLA due to its higher temperature resistance, and problems will be more severe if using a non-heated build plate.

The lower viscosity of PLA+ compared to PLA makes it more likely to cause clogging as it passes through the extruder and nozzle, while users of PLA+ filament have also reported occasional issues with stringing.

Surface quality

Manufacturers offering PLA+ filament tend to market their product as a high-quality version of PLA, promising a good surface finish on printed parts. eSun says its PLA+ material has “good glossiness.”

Although there is no clear reason why PLA+ offers this advantage, users often agree that PLA+ can provide a smoother finish than standard PLA. 

Color

Enhanced PLA filaments can be colored with pigments, as with standard PLA. However, the limited number of material developers offering a PLA+ product range means that there are fewer color options for PLA+ than there are for PLA. There are also very few transparent filament options for PLA+.

Note that the introduction of pigments can affect the mechanical properties of a thermoplastic.[4] Because of this, manufacturers of PLA+ may avoid certain pigments that negatively affect properties like strength and temperature resistance.

Storage

Both PLA and PLA+ should be stored in a way that prevents moisture absorption. Both filaments can benefit from being stored in vacuum-sealed bags, while dedicated filament drying machines — used before or during printing — can result in superior performance.

Price

As a rule, material manufacturers that sell both PLA and PLA+ filament typically put a slightly higher price on PLA+, as it is supposed to offer better performance and print quality. On Amazon, eSun PLA+ costs around $26/kg, while the same company’s regular PLA filament costs around $23/kg.

Using eSun as an example, the price difference between PLA and PLA+ is clearly quite small. Furthermore, premium-brand “standard” PLA can often cost more than budget-brand PLA+. For instance, Makerbot’s high-quality METHOD PLA filament costs around $86/kg, far more than eSun PLA+.

Conclusion

Material developers market their PLA+ filament as a high-quality version of PLA that produces some advantages over the standard version of the filament. As we have seen, PLA+ usually delivers on those promises, offering superior toughness and layer adhesion, as well as other benefits. Thousands of 3D printer users have reported positive results using common PLA+ filament brands like eSun and Overture, proving that these materials can work well under the right printing conditions.

However, we should also remember that the term “PLA+” is not a guarantee of quality, and a standard PLA from a trusted filament brand may well outperform a PLA+ from an unknown seller.

Furthermore, while the material characteristics of PLA+ may be suitable for certain 3D printing projects — printing parts to be used in high-temperature environments, for example, or parts that require a high level of impact resistance — they may be unsuitable for others. For instance, FFF printers that lack high-temperature capabilities (or that do not have heated beds) may be better suited to printing standard PLA, which has a low melting point.

Finally, buyers of FFF filament should remember that neither PLA nor PLA+ are particularly high-performing thermoplastics, and they are more often used for prototyping than functional parts. If a 3D printed part will be subject to high levels of stress, it may be better to use an engineering plastic like POM or nylon, or even a high-performance plastic like PEEK, rather than opting for the marginal gains offered by PLA+. In other words, while PLA Plus filament can make PLA parts better, it cannot perform miracles.

References

[1] Humphreys R. From Corn to Poly Lactic Acid (PLA): Fermentation in Action [Internet]. Polymer Innovation Blog. Innocentrix, LLC; 2012 [cited 2021Dec19]. Available from: https://polymerinnovationblog.com/from-corn-to-poly-lactic-acid-pla-fermentation-in-action/

[2] Cuiffo MA, Snyder J, Elliott AM, Romero N, Kannan S, Halada GP. Impact of the fused deposition (FDM) printing process on polylactic acid (PLA) chemistry and Structure. Applied Sciences. 2017;7(6):579.

[3] Elongation at Break or Fracture Strain: Technical Properties of Plastics [Internet]. Omnexus. SpecialChem; [cited 2021Dec19]. Available from: https://omnexus.specialchem.com/polymer-properties/properties/elongation-at-break

[4] Soares JB, Finamor J, Silva FP, Roldo L, Cândido LH. Analysis of the influence of polylactic acid (PLA) colour on FDM 3D printing temperature and part finishing. Rapid Prototyping Journal. 2018 Nov 12.