The global interest in sustainability has spotlighted bioplastics and biomass plastics (i.e., plastics made from plants) like Polylactic Acid (PLA).

We’re frequently asked, “Is PLA actually plastic?” The answer: Yes.

PLA exhibits all the same properties as its petroleum-based siblings but uses renewable and compostable resources. Let’s learn more about this eco-conscious alternative.

What are PLA resins?

Typically represented as (C3H4O2)n, Polylactide (polylactic acid, PLA) is a biodegradable thermoplastic polymer built on lactic acid monomers. PLA uses glucose derived from fermented plant starches, such as corn or sugarcane to produce lactic acid, which is chemically converted to produce a compound called lactide and then polymerized to produce PLA.

PLA is both a biomass plastic and a biodegradable plastic. While it has less environmental impact, it should be noted that PLA does not readily decompose in the natural environment; it requires industrial composting conditions. Biodegradable PLA is hydrolyzed through the heat and moisture present in industrial composting and ultimately decomposed into carbon dioxide and water by microorganisms. 

Polylactic Acid Properties 

PLA has a wide range of physical and mechanical properties, making it environmentally and esthetically friendly. PLA features include: 

• Temperature:
  The PLA melting point, which ranges between 150°C and 180°C, makes it easy to process using injection molding and 3D printing.
• Density:
  Compared to other common plastics, PLA has a density of about 1.24–1.25 g/cm³, giving it a solid feel and excellent structural integrity.
• Tensile strength:
  The tensile strength of PLA ranges from 50 to 70 MPa, which can be affected by additive blending.
• Stability:
  PLA shows limited chemical resistance. It tolerates short-term exposure to oils, fats, and alcohols (e.g., ethanol) but is susceptible to hydrolysis and can be attacked by strong acids, bases, and certain organic solvents.
• Elasticity:
  PLA’s Young’s (elastic) modulus is relatively high, making it ideal for items where shape retention is important. 
• Color:
  PLA film is naturally transparent and often used when a clear, glossy appearance is needed.

Additional PLA physical property values: 

While the benefits of PLA are attractive, it does have disadvantages, like: 

• Heat resistance:
  ⁠The PLA softening temperature (i.e., glass transition temperature) range limits its use in high-heat settings.
• Poor impact strength:
  ⁠Compared with many plastics, PLA has low impact toughness and limited ductility, making it more susceptible to cracking under stress, especially at low temperatures. 
• Low durability:
  ⁠PLA’s structural integrity can be compromised by hydrolysis or exposure to strong acids, bases, and certain organic solvents; rather than “dissolving,” it may soften, swell, embrittle, or degrade.
• Limited mechanical strength:
  ⁠⁠PLA does not hold well to repeated mechanical stress and can fail under these conditions.

Materials are being developed to improve these properties. For example, there are methods to make petroleum-based plastics into polymer alloys, use fillers as reinforcement and mix PLA with different configurations.

Polylactic Acid Uses

PLA is popular thanks to its versatility, biodegradability, manufacturing simplicity, and more because it maintains product performance while reducing carbon footprint. It is commonly found in: 

• Packaging:
  Since it meets food hygiene standards, PLA packaging is frequently used for disposable cups, containers and wraps.
• Medical devices:
  ⁠Using PLA in sutures and implants like screws and plates eliminates the need for surgical removal because they degrade on their own over time.
• Textiles:
  PLA fibers are known for their softness and moisture-wicking. They are used in activewear, undergarments, upholstery, baby wipes and hygiene products. 
• Agriculture:
  PLA resins can be converted to mulch films that limit weed growth and retain soil moisture while decomposing naturally.

Though PLA is not yet as commonly used as petroleum-based plastics and still has some issues to overcome, the market is expected to expand as sustainability initiatives expand.