What is (PLA) Polylactic Acid?

Polylactic acid (PLA) is a biodegradable polymer derived from lactic acid. It is a highly versatile material and is made from 100% renewable resources like corn, sugar beets, wheat and other starch-rich products. Polylactic acid exhibits many properties that are equivalent to or better than many petroleum-based plastics, which makes it suitable for a variety of applications.

It is important that PLA compares well with other popular plastics already used for packaging. It is clear and naturally glossy like the polystyrene used in “blister packs” for products such as batteries, toys, and many others. PLA is resistant to moisture and grease. It has flavor and odor barrier characteristics similar to the popular plastic polyethylene terephthalate (PET) used for soft drinks and many other food products. Tensile strength and modulus of elasticity of PLA is also comparable to PET.

PLA can be formulated to be either rigid or flexible and can be copolymerized with other materials. Polylactic acid can be made with different mechanical properties suitable for specific manufacturing processes, such as injection molding, sheet extrusion, blow molding, thermoforming, film forming and fiber spinning using most conventional techniques and equipment.
PLA is a nonvolatile, odorless polymer and is classified as GRAS (generally recognized as safe) by the Food and Drug Administration in the United States.

How Is PLA Made?

The starting material for polylactic acid is starch from a renewable resource such as corn. Corn is milled, which separates starch from the raw material. Unrefined dextrose is then processed from the starch. Dextrose is turned into lactic acid using fermentation, similar to that used by beer and wine producers.

Turning the lactic acid into a polymer plastic takes some specialized chemistry. Through a chemical process called condensation, two lactic acid molecules are converted into one cyclic molecule called a lactide. This lactide is purified through vacuum distillation. A solvent-free melt process causes the ring-shaped lactide polymers to open and join end-to-end to form long chain polymers. A wide range of products that vary in molecular weight and crystallinity can be produced, allowing the PLA to be modified for a variety of applications.

How long does PLA take to biodegrade in a landfill?

PLA is fully compostable and biodegradable. In commercial composting conditions, PLA will compost in approximately 30-45 days. Composting may take longer in a home composting bin. PLA will react in landfills like other organic waste such as food.

Michael Tasker

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