What is PLA? From Crops to PLA
Polylactic Acid (PLA), abbreviated as PLA, is the most commonly used material in FDM (Fused Deposition Modeling) as it’s affordable, stable, and easy to print. The bio-based characteristic that PLA commonly uses on crops like corn, sugarcane, and cassava as its raw material makes it eco-friendly and bio-degradable.
To achieve better 3D printing results, many companies work to improve the properties of PLA. They have developed various modified PLAs based on the original PLA filament. These PLAs include PLA+, PLA Meta, Silk PLA, Rainbow PLA, Marble PLA, Twinkling PLA, and wood PLA composites. PLA filament is the most basic 3D printer filament and forms the main component of most specialty 3D printer filaments. PLA is so important that we must have an in-depth understanding of it.
While PLA filament is extensively explored, few are privy to the complete and full production process. This article will delineate the process of how PLA is transformed from a bio-material into plastic, and at the end of the article, a comparison of PLA and other materials will be shown.
The History of PLA
In 1857, Marcellin Berthelot, a French chemist, discovered lactic acid, an organic acid, by hydrolyzing ammonium lactate. Ten years later, he successfully fermented glucose into lactic acid for the first time, laying the foundation for the industrial production of lactic acid. In the early 20th century, ICI (Imperial Chemical Industries) developed a technology to ferment starch raw materials to produce lactic acid and built the world's first large-scale lactic acid fermentation production device in 1930. Since then, low-cost lactic acid production by fermentation method has become possible, creating conditions for the development and application of PLA.
In 1932, Chemist Carothers of DuPont first synthesized high molecular weight polylactic acid(PLA) by direct polymerization of lactic acid, which marked the birth of PLA polymers. In 1954, British chemist Darby synthesized the first biodegradable polymer, Poly-Hydroxyalkanoates (PHAs), from PLA. Subsequent studies showed that PHA and PLA both have biological activity and good bio-compatibility, making them a trend of research in the biomedical field.
Entering the 21st century, with the development of polyester chemistry and polymer chemistry, research on lactic acid and PLA made great progress. Preparation methods, polymerization mechanisms, and performance control were well understood. PLA, meanwhile, has become the well-suited and main material for 3D printing, promoting the widespread application of 3D printing technology in family education and industrial design. This makes 3D printing a powerful tool for customized production and customization.
How PLA Filament is Created
Step 1: Raw Material Selection
PLA, a biodegradable polymer, is typically synthesized from plant-based sources such as corn starch or sugarcane and other grains. These materials are suitable for PLA with their high yield and low cost. Mostly composed of glucose units with large molecular weights, these starches require further processing to convert into lactic acid, the raw material for Poly-lactic acid(PLA)
Step 2: Starch Gelatinization
Mix the starch granules with water and apply heat under pressure until the starch is completely dissolved to constitute a starch slurry. Generally, the process will be under 130-170°C and 0.5-2 MPa for 30-60 minutes and mandates precise control of duration, temperature, and pressure to prevent starch degradation and quality defects. The starch gelatinization rate commonly attains 85% or higher.
Step 3: Saccharification and Fermentation
Apply a composite saccharifying enzyme at 55-65°C and pH 5.5-6.5 to transform the starch slurry into glucose. Then inoculate lactobacillus in an anaerobic environment to ferment for 24-36 hours, transforming glucose into lactic acid, with a concentration of 10-15%. This process necessitates sterility and rigorous control of conditions to maximize yield, which is commonly 80% or better.
Step 4: PLA Polymerization
This process requires two procedures - Low Polymerization and High Polymerization. With the aid of a catalyst, low Polymerization takes place, lasting 1-3h, subsequently followed by high Polymerization lasting 3-5h at higher temperatures. These two reactions' duration and temperature require stringent control to accomplish the target product.
Step 5: Purification
Undesirable components, such as impurities, unreacted substances, low polymerization, and unconverted monomers, need to be removed from the fermentation liquid. This step culminates in the acquisition of purified, highly polymerized PLA, 99.5% or higher. This step is crucial for product performance.
Step 6: Processing
High-purity PLA can be attained through the above sequence of procedures. Then PLA is processed into fibers, pellets, and films through extrusion or injection molding at 190-220°C. Subsequently, the PLA undergoes a winding machine process, transforming it into the filaments you most commonly use.
In summary, PLA production requires precise control of complex biochemical processes and a high degree of technical expertise. Each step has specific parameters and conditions that must be carefully regulated to achieve the desired product. Maintaining high standards of quality and purity throughout the process is essential. With its sustainability and biodegradability, PLA has become an important material for 3D printing.
Properties of PLA
While PLA is both fundamental and crucial, its mechanical properties are average. PLA-printed parts have relatively poor impact resistance and lower dimensional precision. The surfaces of PLA 3D-printed objects are fairly rough and require post-processing to achieve a shiny finish.
The characteristics of PLA can be further observed by comparing it with other 3D printer filaments:
- PLA and PLA+: The toughness and impact, and temp-resistance of PLA+ are not as good as PLA+. In some occasions with high requirements, PLA+ is more suitable for its improved toughness, impact, and temp-resistance. That’s why we regard it as “PLA PLUS.”
- PLA and TPU: When it comes to elasticity, toughness, and high impact strength, TPU is undoubtedly the winner, making it an ideal material for shock-absorbing and buffering because it has an elongation at break of up to more than 800% and its tensile strength can reach be 35MPa.
- PLA and PETG: PETG is more chemically stable than PLA. Plus, PETF is tougher and also has higher impact strength than PLA. The IZOD Impact Strength of PETG is nearly 1.5 times of PLA. But the 3D printing surface finish is not good as PLA.
- PLA and ABS: ABS has relatively high hardness, toughness, and impact strength. The IZOD Impact Strength of ABS can reach 29KJ/㎡, nearly 5 times of PLA. ABS is also more resistant to high temperatures.
Advantages of PLA in 3D Printing
Below are the main benefits of PLA filament:
1. Ease of Use: PLA is relatively easy to work with, making it ideal for beginners and hobbyists. It has low printing temperatures, less warping, and better adhesion to build platforms.
2. Wide Color Options: It is available in a wide range of vibrant colors, allowing for creative and colorful 3D prints.
3. Biodegradability: PLA is derived from renewable resources such as cornstarch or sugarcane. It is biodegradable, making it more environmentally friendly compared to other plastics used in 3D printing.
4. Minimal Odor: PLA has a minimal odor during printing, making it more pleasant to work with compared to some other filaments.
5. Good Print Quality: PLA filament produces high-quality prints with excellent surface finish and detail. It is ideal for intricate designs, decorative objects, and prototypes.
6. Low Warping and Shrinkage: PLA has low warping and shrinkage tendencies, which means it maintains dimensional accuracy and stability during the printing process.
7. Compatibility: PLA is compatible with most 3D printers on the market. It works well with both heated and non-heated build platforms.
8. Fast Cooling: PLA cools quickly after extrusion, leading to shorter print times and enhanced print stability.
9. Safe and Non-Toxic: PLA is considered safe to use and is non-toxic. It doesn't emit harmful fumes during printing, making it a preferred choice for educational and household settings.
10. Post-Processing and Finishing: PLA can be easily sanded, painted, or post-processed to achieve the desired final look and texture of the printed object.
Best 3D Printing Software
There are a lot of 3D printing software available, but we recommend using SelfCAD. SelfCAD is a browser-based and downloadable 3D modeling and slicing software designed for both beginners and professionals in the field of 3D design and printing. It provides a user-friendly interface and a comprehensive set of tools and features to create, modify, and prepare 3D models for printing.
The software provides a range of powerful 3D modeling tools, including basic shapes, advanced modeling tools, sculpting brushes, and 3D text creation tool. These tools allow users to create intricate and detailed 3D models from scratch. SelfCAD includes sculpting tools that allow users to sculpt and shape 3D models in a way similar to working with clay. This feature is particularly useful for creating organic and artistic designs.
You can also analyze and repair mesh issues, optimize models for printing, and even prepare designs for 3D printing using the in-built online slicer of the software and this eliminates the need for third-party slicing software, streamlining the workflow.
Enjoy powerful modeling, rendering, and 3D printing tools without the steep learning curve.
Need to learn 3D modeling? Get started with interactive tutorials.