Mastering PLA 3D Printing Filament: Composition, Properties, and Key Differences

PLA (polylactic acid) filament is one of the most commonly used in fused deposition modeling (FDM) 3D printing because it’s easy to work with and looks great. In the history of plastics, PLA is the OG (well, one of them). It was invented in 1938 by DuPont chemist Wallace Carothers (who also, coincidentally, invented nylon), but took quite a long time to become mainstream. In the ‘50s, large manufacturing product materials companies started doing more in-depth research on it, and by the ‘90s, PLA was on the market commercially. It was first adopted as a biodegradable PET alternative and has since been used for everything from packaging and disposable cutlery to appliances and devices. When 3D printers emerged in the late '00s, PLA was one of the first filament materials used and, today, it accounts for more than 40% of the plastics used in additive manufacturing. 

What is PLA 3D Printing Filament?

PLA is a thermoplastic polymer made by fermenting plant products like sugarcane or cornstarch to produce lactic acid, which is then polymerized into PLA, often using lactide. It can then be mixed with nucleating agents or plasticizers (i.e., polyethylene glycol) to change its properties. For extra benefits, it can also be mixed with other materials like wood fibers, carbon, metal flakes, graphene, etc. It’s then extruded into filament or fiber. The PLAs with simpler ingredient lists are known as PLA, while the ones chock full of enhancers are referred to as PLA+.

• PLA: Close to the pure polymer but may contain limited amounts of additives to modify various properties, including intramolecular flexibility, melt viscosity, and color or visual properties.
• PLA+: Likely to contain significant quantities of a wide range of additives. These include carbon fiber for model stability, stiffness, and increased UTS (ultimate tensile strength); wood fiber for cosmetic effect; graphene for stiffness and increased UTS; and metal particles for cosmetic effect.

For more information on their similarities, differences, and uses, have a look at our guide: PLA vs. PLA+ 3D Printing.

Among PLA’s desirable properties is its intra-layer bonding, which allows newly extruded plastic to bond very well with plastic that has been recently cooled. The strands and layers blend effortlessly together for a smooth (and pretty) surface, and this doesn’t change much even if you switch up the machine’s settings. It also has a good tolerance to a range of extruding temperatures so that you can use it on many different machines. This makes it super easy to print with and a great starter 3D printing filament for those without much experience.

You can use PLA for items that need to be attractive, but not necessarily long-lasting. The material can’t take a lot of stress, so you wouldn’t want to make machine parts, engineering test pieces, or bearing-type components from it. It can’t survive being left outdoors and doesn’t hold up well when faced with water, chemicals, or abrasion. Also, just because it’s made from “green” materials, that doesn’t automatically make it eco-friendly. PLA needs to be separately recycled, and it’s only biodegradable if commercially composted.

What is the Composition of PLA Filament?

PLA filament is a polymer resulting from the fermentation of plant sources such as sugar cane, taro, and cornstarch. It falls into two broad categories:

1. PLA: Close to the pure polymer but may contain limited amounts of additives to modify various properties, including: intramolecular flexibility, melt viscosity, and color or visual properties.
2. PLA+: Likely to contain significant quantities of a wide range of additives. These include: carbon fiber for model stability, stiffness, and increased UTS (ultimate tensile strength); wood fiber for cosmetic effect; graphene for stiffness and increased UTS; as well as metal particles for cosmetic effect.

What are the Properties of PLA Filament?

All the important properties of PLA filament are listed in the table below.