Polylactic acid, also known as PLA, is a thermoplastic monomer. It comes from renewable organic sources such as corn starch or sugar cane. This means that PLA is different from most plastics. Instead of breaking down into persistent microplastics, it degrades completely in the presence of water (hydrolysis). This is a promising way forward as more and more microplastics become a persistent problem at the end of their life. These were discovered by Hydra Marine Sciences in a study commissioned by the Dutch Bioplastics Association, which advances bioplastics knowledge globally. PLA is a bio-based polymer made entirely from fermented plant sugars. The study showed that in an aqueous environment, PLA will hydrolyze into smaller sized molecules (hydrolysis).
1. Lactic acid
Hydrolysis is an abiotic process that occurs in the presence of moisture or humidity. In this case, PLA breaks down into smaller pieces. The rate at which this occurs is determined by temperature. Eventually, the polymer chains are so short that the material becomes soluble in water. It is then biodegraded by microorganisms into biomass, water and carbon dioxide. In other words: these processes do not produce toxic substances. Lactic acid, the monomer structural unit of PLA, is classified as safe and non-toxic in both the US and the EU. The same applies to the food contact requirements of many PLA grades. In addition, specific grades of PLA have been approved and used for decades in medical applications such as sutures and tissue scaffolds. These substances are safely absorbed and bioassimilated by the body after use. We now use it to make a wide variety of products: cups, cutlery, trash can liners, flexible food packaging. In other words, PLA seems suitable to overcome at least part of the microplastic problem.
2. Microplastics, an underestimated problem
Microplastics form a problem being underestimated by the industry. Consumer sentiment may be far ahead of industry policy in this regard, warns Lux Research's Anthony Schiavo, which could spark a backlash. He argued that before the backlash really begins, companies need to proactively respond to consumer sentiment by identifying and developing the worst sources of microplastics and directly engaging in microplastic cleanup efforts and technologies. Others agreed with this sentiment. On the one hand, we need to choose more responsible materials for the products we rely on; on the other hand develop a better infrastructure for plastics collection and waste disposal, says Erwin Vink, a member of the board of directors of Bioplastics Netherlands. PLA will be part of that solution, as it will not have the long-term effects of current micro- and nanoplastics, which are the final stage of non-biodegradable substances. Even so, for PLA, we should avoid littering the environment.
3. Biodegradable plastics
Fortunately, there are more biodegradable plastics such as polylactic acid, polyhydroxyalkanoates (PHA), starch blends, cellulose-based plastics and lignin-based polymer composites. PLA stands out because not only is it environmentally friendly, but it's also an inexpensive and versatile plastic. And it has a low carbon footprint. We produce lactic acid from plant sugars through fermentation and then polymerize it into PLA, a polylactic acid biopolymer. Wikipedia says that PLA, has become a popular material because it is economically produced from renewable resources.In 2021, PLA is the world's highest consumer of bioplastics.PLA is the most widely used plastic filament material for 3D printing because it has a low melting point, high strength, low thermal expansion and good layer adhesion. It has many properties that may make it the most widely used plastic in the world.
