What is PLA (Polylactic acid)?
Polylactic acid, also known as PLA, is a thermoplastic monomer derived from renewable, organic sources such as corn starch or sugar cane.
Using biomass resources makes PLA production different from most plastics, which are produced using fossil fuels through the distillation and polymerization of petroleum.
Despite the raw material differences, PLA can be produced using the same equipment as petrochemical plastics, making PLA manufacturing processes relatively cost efficient.
PLA is the second most produced bioplastic (after thermoplastic starch) and has similar characteristics to polypropylene (PP), polyethylene (PE), or polystyrene (PS), as well as being biodegradeable.
PLA has become a popular material due to it being economically produced from renewable resources and the possibility to use it for compostable products.
In 2024, PLA had the highest consumption volume of any bioplastic of the world, with a share of ca. 26 % of total bioplastic demand. With an annual increase rate of 2.5% of the bioplastic market, the global bioplastics production capacity is increased from around 2.11 million tons in 2020 to approximately 2.87 million tons in 2025.
Although 43% of these manufactured products are biodegradable, and 30% of these products are known as both bio-sourced and biodegradable.
Although its production is growing, PLA is still not as important as traditional commodity polymers like PET or PVC. Its widespread application has been hindered by numerous physical and processing shortcomings.
PLA is the most widely used plastic filament material in FDM 3D printing, due to its low melting point, high strength, low thermal expansion, and good layer adhesion, although it possesses poor heat resistance unless annealed.
Although the name “polylactic acid” is widely used, it does not comply with IUPAC standard nomenclature, which is “poly(lactic acid)”. The name “polylactic acid” is potentially ambiguous or confusing, because PLA is not a polyacid (polyelectrolyte), but rather a polyester.
Types OF PLA (Polylactic acid)
There are three main types of PLA – PDLA, PLLA, and PDLLA. Get to know the properties of each.
- PDLA (Poly-D-Lactic Acid). PDLA biodegrades more slowly than other types of PLA.
- PLLA (Poly-L-Lactic Acid). PLLA is most commonly used in 3D printing and injection molding. PLA+, a type of 3D printing material that is stronger than regular PLA, is also typically made with PLLA, albeit with strength-increasing additives.
- PDLA (Poly-D-Lactic Acid). PDLA breaks down more quickly than other types of PLA, making it a good choice for pharmaceutical applications that will be ingested by humans or animals.
Additionally, PLA is available in many colors and finishes, such as matte, glossy, and silk. It can also be purchased in hybrid form – containing a mix of PLA and materials such as wood, or with additives that increase properties such as strength or flexibility.
- Wood Filaments: PLA is mixed with woods such as bamboo, cedar, coconut wood, cork, pine, or walnut. This can, for example, be used to give PLA printed furniture a natural-looking appearance.
- Metal Filaments: Mixing PLA with metals such as brass, bronze, copper, iron and steel can make printed parts stronger and glossy.
- Other Filaments: PLA can also be mixed with other materials and substances, including carbon fibre, conductive carbon and even beer or coffee (to add a scent to printed items). PLA filaments can also be given colour-changing properties.
Over the years, many unique types of PLA filament have emerged, giving the consumer many choices:
Standard & Recycled
First and foremost, standard PLA is the regular type of PLA prevalent in the 3D printing industry, with no unique or special features besides the basic properties of the PLA material and the best affordability.
Not much different from standard options, recycled PLA is becoming increasingly available and is of excellent quality when purchased from trusted manufacturers.
Aesthetic
Here’s where PLA really shines – literally. As a great choice for decorative prints, filament manufacturers have gotten very creative with the possibilities (although we can’t promise any strength-wise benefits).
One of the most common variants is silk PLA, which yields a super shiny, smooth, and silky finish to parts, popular for pieces such as vases. Glittery or sparkly PLA contains large glitter particles that are very visible, so you can have a printed part that sparkles.
Glow-in-the-dark PLA will luminesce in the dark due to special additives in the filament. There are also dual-color, rainbow, and gradient filaments to give PLA parts a colorful pop, no paint required. For a unique look, try out transparent or matte PLA filaments.
Taking a slightly different approach to aesthetic filaments, composite filaments aimed at mimicking a natural material can elevate 3D prints to a new level.
Wood PLA often contains actual wood particles to give it a realistic carven-wood appearance, great for prints like plaques.
Marble PLA filament is another popular option, and sometimes (but not always) contains small particles of stone to yield a marble-like, speckled finish.
Functional
“Plus” and “Pro” are common terms in the filament business to describe a material that has been mixed with special additives to enhance its performance, usually concerning its strength.
Pro PLA and PLA+ are great options if you want to print functional, real-world-use parts that will be subject to physical stresses but in a material that’s still easy to print.
For even more strength, carbon fiber PLA is a composite filament that contains carbon fiber particles to increase the PLA’s strength and durability while maintaining most of its ease-of-use properties.
Aside from filaments formulated for strength, there are PLA variants that aim to improve other important physical properties.
These include soft PLA, a flexible TPU-like filament, heat-resistant PLA, and conductive PLA for low-magnitude electrical projects.
Properties of PLA (Polylactic acid)
PLA is soluble in solvents including dioxane, hot benzene, and tetrahydrofuran. The physical and mechanical properties differ according to the exact type of polymer, ranging from an amorphous glassy polymer to a semi or highly crystalline polymer with a glass transition of 60–65 °C, a melting temperature 130-180 °C, and a tensile modulus of 2.7–16 GPa.
Heat resistant PLA can withstand temperatures of 110 °C, and the melting temperature can be increased by 40–50 °C and the heat deflection temperature can be increased from around 60 °C to as much as 190 °C by physically blending the polymer with PDLA (poly-D-lactide).
Annealing, adding nucleating agents or forming composites with other materials can all change the mechanical properties of PLA.
However, the basic mechanical properties of PLA range between those of polystyrene and PET, with similar properties to PET but a lower maximum continuous use temperature.
The high surface energy of PLA makes it ideal for 3D printing. PLA can also be solvent welded using dichloromethane, while acetone softens the surface of the material, making it sticky without dissolving it so it can be welded to another PLA surface.
Ethylacetate can be used as an organic solvent, dissolving PLA and making it a good solution for removing PLA printing supports or cleaning 3D printing extruder heads.
Propylene carbonate and pyridine can also be used as a solvent, but are less favourable than ethylacetate and propylene carbonate, being less safe in the first instance and emitting a distinct bad fish odour in the second.
Here are the general properties of PLA:
| Property | Value |
| Heat Deflection Temperature (HDT) | 126 °F (52 °C) |
| Density | 1.24 g/cm³ |
| Tensile Strength | 50 MPa |
| Flexural Strength | 80 MPa |
| Impact Strength (Unnotched) IZOD (J/m) | 96.1 |
| Shrink Rate | 0.37-0.41% (0.0037-0.0041 in/in) |
Although we’ve already mentioned a few material properties, such as brittleness, PLA plastic has many other properties worth discussing:
- Strength: PLA isn’t a plastic known for its strength (that would be nylon or PC), but a PLA part’s strength is more dependent on how it was made rather than the material itself. For example, using a higher infill density and layer height would yield a stronger 3D printed part.
- Flexibility: PLA is a stiff plastic, meaning it has a low flexural strength compared to other plastics, especially flexible ones such as TPU. Additionally, as we’ve mentioned, PLA is brittle. Instead of bending, it usually snaps and br eaks.
- Temperature resistance: PLA requires relatively low printing temperatures, but this also means it’ll be less resistant to elevated temperatures after printing. This is why it’s recommended that you not use PLA for parts that are meant to be outdoors or to be used in direct sunlight, as they can easily become disfigured. And, as seen above, avoid the dishwasher if the parts need to be washed.
- UV resistance: PLA can discolor when exposed over long periods to UV rays. In combination with high temperatures, this degradation can be faster and cause embrittlement.
- Chemical resistance: PLA isn’t soluble in solvents such as acetone or isopropyl alcohol and, overall, PLA plastic is a chemically resistant and stable material. However, you can still use solvents such as ethyl acetate and mixtures like XTC3D to dissolve or layer-smooth PLA parts.
How is PLA made?
PLA is a type of polyester made from fermented plant starch from corn, cassava, maize, sugarcane or sugar beet pulp. The sugar in these renewable materials are fermented and turned into lactic acid, when is then made into polylactic acid, or PLA.
There is more detailed information on PLA production methods below.
Production methods For PLA (Polylactic acid)
There are several industrial ways to produce usable PLA with a high molecular rate. Lactic acid and the cyclic di-ester, lactide are the two main monomers used for this.
The most common method of creating PLA is ring-opening polymerisation of lactide with various metal catalysts (typically tin octoate) either in a solution or as a suspension.
The metal-catalysed reaction tends to lead to recemisation of the PLA, which reduces stereoregularity when compared to the biomass starting material.
It is also possible to produce PLA through the direct condensation of lactic acid monomers. This process is carried out at temperatures under 200 °C, at which point an entropically favoured lactide monomer is generated.
This process generates water equivalent to each esterification step. The water needs to be removed either by using a vacuum or through azeotropic distillation to promote polycondensation and attain a high molecular rate.
Even higher molecular rates can be achieved by crystallising the crude polymer from the melt. This concentrates carbolyxic acid and alcohol end groups in the amorphous region of the solid polymer, reacting to achieve molecular weights of 128–152 kDa.
By polymerising a racemic mixture of L- and D-lactides, it is possible to synthesise the amorphous poly-DL-lactide (PDLLA).
Stereospecific catalysts can lead to heterotactic PLA, that has been known to show crystallinity. The degree of this crystallinity is controlled by the ratio of D to L enantiomers that are used, as well as by the type of catalyst that is used.
The five-membered cyclic compound lactic acid O-carboxyanhydride (lac-OCA) has also been used in academic surroundings instead of lactic acid and lactide. This compound doesn’t produce water as a co-product and is more reactive than lactide.
PLA has also been directly biosynthesised while lactic acid has also been contacted with a zeolite, creating a one-step process that takes place at a temperature that is around 100 °C lower.
Is PLA environmently friendly?
Around the world, PLA has been advertised as a renewable, biodegradable, plant-based alternative to petroleum-based plastics.
Due to PLA being made from fermented starch, the plastic was said to be “carbon-neutral” and “non-toxic”, so many businesses made the switch from their petroleum products.
With reducing plastic consumption in mind, PLA seemed to be a win in terms of sustainability and became a popular alternative. Unfortunately, as more information has come to light, it became apparent this is far from the truth.
When taking a look further into PLA plastics, many environmental issues revealed that zero waste was a complicated and unattainable path. The biggest problem with PLA is the very specific conditions needed in order for it to be properly composted.
Instead of being recycled with regular plastic materials, PLA needs to be sorted separately and brought to a ‘closed composting environment’ as otherwise it contaminates the recycling stream.
However, when sent to industrial composting facilities it is then essential that PLA plastics are heated to 140 degrees and exposed to special digestive microbes that can biodegrade.
So, with the demanding conditions for biodegradation and the fact that it biodegrades very slowly, combined with the increased pressure on consumers to ensure their PLA waste is being sent to the right facility, makes it practically impossible for the products to complete their life cycle as marketed.
It’s thought that because of these difficulties, PLA plastics more often than not end up in landfills or oceans – so not as sustainable as it may seem!
There is also the issue that many big cities do not even have the correct industrial facilities for the process, which leads to the PLA being discarded into landfills.
Analysts have even estimated that a PLA bottle could take anywhere from 100 to 1,000 years to decompose in a landfill, and if that isn’t bad enough, as it decomposes it releases methane – a gas 23 times more potent than Carbon dioxide.
There are other factors to consider as to why PLA is not as sustainable as first thought. For example, the fertilisers and pesticides used to grow the plants that make up PLA could release more pollutants.
The fertilisers used to grow PLA feedstock are also responsible for a large amount of GHG emissions. Not only that, but the amount of water needed to make PLA is 38% more than polypropylene and 10% more than PET.
In order for PLA to be a sustainable, eco-friendly solution, sufficient sorting and reliable composting systems must be in place. If it isn’t, PLA really is not much better to traditional plastic.
Advantages of PLA (Polylactic acid)
Production
- PLA is made from renewable raw materials.
- It has a reduced carbon footprint compared to fossil-based plastics. two reasons:
- crops absorb co2 when growing;
- It takes less energy and this produces less greenhouse gas to produce PLA than fossil-based plastic
- PLA is made in the USA (NatureWorks Ingeo)
Material
- PLA melts more easily because it has a lower melting point than many fossil-based plastics. It’s easy to work with PLA and it requires less energy to transform.
- One of the two most used plastics in 3D printing (45% market share). It has a low melting point, inexpensive, easy-to print, no fumes. It’s the best option in case of 3D printing.
End-of-life
- PLA is compostable
- When PLA is Incinerated, it emits less toxic fumes than oil based plastics
- Food Contamination of food packaging is not a problem, unlike with plastic recycling.
- In case of biomedical use, PLA degrades into non-toxic acid
Disadvantages of PLA (Polylactic acid)
Production
- Price – PLA is more expensive than fossil-based plastics
- 1st generation uses food crops
- When using crops to produce plastics; one should beware of Intensive agricultural practices, over using fertilisers and GMO, mono cultures and the destruction of natural habitats.
End of Life
- Compostable
- It doesn’t compost fast enough for industrial composters.
- The residue is not compost. it doesn’t improve the quality of soil. No nutrient.
- It changes the PH value of the soil. It makes it more acidic.
- Recyclable – PLA has a lower melting point and cannot be recycled with other plastics. There’s not enough PLA and it’s too dispersed to make recycling economically viable.
Material
- Low melting point makes PLA unsuitable for high temperature applications. PLA may even show signs of getting soft or deforming on a hot summer day.
- PLA has a higher permeability than other plastics. Moisture and oxygen will go through it more easily than other plastics. This will result in faster food spoilage. PLA is not recommended for long-term food storage applications.
- PLA is not the hardest or toughest plastic. PLA is not suitable for applications where toughness and impact resistance are critical.
Applications of PLA (Polylactic acid)
PLA is mainly used for short-lived and disposable packaging. In 2022, of the total PLA production, ca. 35 % was used for flexible packaging (e.g. films, bags, labels) and 30 % for rigid packaging (e.g. bottles, jars, containers).
With an annual increase rate of 2.5% of the bioplastic market, the global bioplastics production capacity is increased from around 2.11 million tons in 2020 to approximately 2.87 million tons in 2025.
Consumer Goods
PLA is used in a large variety of consumer products such as disposable tableware, cutlery, housings for kitchen appliances and electronics such as laptops and handheld devices, and microwavable trays.
It is used for compost bags, food packaging and loose-fill packaging material that is cast, injection molded, or spun. In the form of a film, it shrinks upon heating, allowing it to be used in shrink tunnels.
In the form of fibers, it is used for monofilament fishing line and netting. In the form of nonwoven fabrics, it is used for upholstery, disposable garments, awnings, feminine hygiene products, and diapers.
PLA has applications in engineering plastics, where the stereocomplex is blended with a rubber-like polymer such as ABS. Such blends have good form stability and visual transparency, making them useful in low-end packaging applications.
PLA is used for automotive parts such as floor mats, panels, and covers. Its heat resistance and durability are inferior to the widely used polypropylene (PP), but its properties are improved by means such as capping of the end groups to reduce hydrolysis.
Agricultural
In the form of fibers, PLA is used for monofilament fishing line and netting for vegetation and weed prevention. It is used for sandbags, planting pots, binding tape and ropes.
Medical
PLA can degrade into innocuous lactic acid, making it suitable for use as medical implants in the form of anchors, screws, plates, pins, rods, and mesh. Depending on the type used, it breaks down inside the body within 6 months to 2 years.
This gradual degradation is desirable for a support structure, because it gradually transfers the load to the body (e.g., to the bone) as that area heals. The strength characteristics of PLA and PLLA implants are well documented.
Thanks to its bio-compatibility and biodegradability, PLA found interest as a polymeric scaffold for drug delivery purposes.
The composite blend of poly (L-lactide-co-D, L-lactide) (PLDLLA) with tricalcium phosphate (TCP) is used as PLDLLA/TCP scaffolds for bone engineering.
Poly-L-lactic acid (PLLA) is the main ingredient in Sculptra, a facial volume enhancer used for treating lipoatrophy of the cheeks.
PLLA is used to stimulate collagen synthesis in fibroblasts via foreign body reaction in the presence of macrophages.
Macrophages act as a stimulant in secretion of cytokines and mediators such as TGF-β, which stimulate the fibroblast to secrete collagen into the surrounding tissue. Therefore, PLLA has potential applications in the dermatological studies.
PLLA is under investigation as a scaffold that can generate a small amount of electric current via the piezoelectric effect that stimulates the growth of mechanically robust cartilage in multiple animal models.