Polylactic acid (also PLA) is one of the most versatile bioplastics today, with its use spanning many industries. According to this data appearing on Statista, it was also the most produced in 2020. So why is it called so and how is it made? In addition to the polylactic acid meaning and manufacturing methods, this article will explain its many uses.
What is Polylactic Acid?
Polylactic acid, also commonly called polylactide (PLA), is a special type of polymer that’s derived from lactic acid molecules, thus its name. It’s typically gotten from the fermentation of natural materials such as plant starch, which makes it a nontoxic and biodegradable type of polymer.
Polylactic acid plastic is a worthy alternative to petrochemicals, given its production from natural materials. In addition to being biodegradable, the plastic is also biocompatible and used in many different medical applications.
But how was this type of plastic discovered and when? After the polylactic acid meaning, let’s see how the plastic came to be—from when it was first made to the present day.
History of Polylactic Acid
The history of polylactic acid takes us back to 1800s when research into its synthesis began. But this research was low-key, and did not yield many results. Other happenings that trace the polylactic acid history are outlined below.
- At the beginning of the 20th century, Wallace Carothers, using what’s called ring-opening polymerization, succeeded in synthesizing a polylactic acid. However, this type of PLA had a low molar weight and, therefore, not commercially viable. Its production method was also quite expensive.
- Later, in the 1950s, a better form of PLA with higher molar weight and more superior properties was made. This marked the beginning of commercial production of polylactic acid and, later, the popularization of its use in different industries.
Today, PLA is the most common type of bioplastic—highly useful and easy to process into different products. This report by Markets and Markets shows the polylactic acid market was valued at US$ 1.0 billion in 2021, with a projected annual growth of 12.24% CAGR to hit 1.9 billion by the year 2026.
What is Polylactic Acid Made of?
Polylactic acid is a type of polyester with thermoplastic properties. As mentioned earlier, this type of plastic is made entirely from natural and renewable materials. In order to help you understand this in more detail, here’s the polylactic acid chemical structure explained.
Polylactic Acid Chemical Structure
The polylactic acid chemical structure is composed of ester bonds that link a chain of lactic acid monomers with chemical formula (C3H4O2)n. This is what gives the plastic its many useful properties.
Due to its lactic acid source, PLA also exist as 3 different families or subgroups: poly (L-lactic acid) or PLLA in short, poly (D-lactic acid) or PDLA, and poly (DL-lactic acid) or PDLLA.
Polylactic Acid Examples
Today, polylactic acid plastic is everywhere. You can see it in packaging materials, for example, such as the eco-friendly PLA shopping bags and food-grade containers, as the material of choice for tea bags, and so on. As medical products, PLA is seen in the sutures and bone screws used by medical doctors.
Polylactic acid is also one of the most popular materials for 3D printing filament, being a thermoplastic with many favorable chemical and mechanical properties. Other polylactic acid examples include its use in making skin care products such as dermal filler and other uses.
How is Polylactic Acid Made?
The synthesis of polylactic acid involves fermenting natural feedstock to produced lactic acid, and then changing the lactic acid to PLA plastic. This can either be done chemically or by use of microbial fermentation.
Microbial or bacterial fermentation is the most used method, mostly due to its being cost-effective. Polylactic acid synthesis also involves two main stages: anaerobic fermentation of feedstock to lactic acid and the changing of lactic acid into plastic.
Lactic Acid Fermentation Materials
Before PLA plastic can be manufactured, raw materials are microbially or chemically fermented to produce lactic acid. Lactic acid fermentation raw materials include starch or sugars from sugarcane, wheat, potatoes, sugar beet, and tapioca roots or cassava.
Raw materials for the production of lactic acid may also include cellulosic materials such as cotton and biomass, or even dairy products; the list is virtually endless.
Lactic Acid to Polylactic Acid
After the lactic acid has been produced, it’s now time to convert it into polylactic acid plastic. This usually involves dehydration and thermally degrading the lactic acid to a lactide dimer. The resulting lactide then undergoes a process of polymerization to produce PLA.
The production of PLA from lactide can be done in 3 different ways: ring-opening polymerization (which is the most used method), direct polycondensation, and azeotropic dehydration condensation. New PLA synthesis processes, such as microwave irradiation are also being advanced.
Applications of Polylactic Acid
The applications of polylactic acid are very wide and varied. They range from packaging materials and medical devices to agricultural mulch and automotive interior components. Here’s is a detailed look at these uses of polylactic acid, including the reasons for each application.
Polylactic Acid Packaging
One of the most popular applications of polylactic acid is in the making of packaging products. Examples of these products include food containers, water bottles, and even as shrink wrap. Polylactic acid packaging is an eco-friendly alternative to petroleum based plastic packaging, given its being biodegradable.
PLA packaging is also nontoxic and safe, especially when used to hold food products. To improve its performance and allow its wide use in the packaging industry, polylactic acid is sometimes mixed with different materials such as other polymers.
Polylactic Acid in Skincare
The application of PLA extends to the cosmetics industry, where doctors use it as dermal filler. Polylactic acid facial fillers involve injecting quantities of the plastic into the skin to improve its structure and encourage collagen production.
The use of polylactic acid in skincare has several advantages over other materials: it’s highly biocompatible, biodegradable, and non-toxic. That means fewer possibilities of risks, both short and long-term.
Polylactic Acid Medical Application
In the medical world, PLA is being used as the preferred material for making bio-compatible implants such as bone screws, plates, anchors, and rods. Inside the human body, the PLA parts degrade over time, all without causing risks to the patient.
PLA medical applications may also involve combining the material with other select polymers to prevent cases of unwanted responses by the body. Nevertheless, polylactic acid is itself a safe product, which is one of the reasons of its wide use in medicine.
Polylactic Acid 3D Printing
Polylactic acid plastic is the most used material for 3D printing filament, mostly due to its thermal properties. For example, you can use it with an extruder temperature of 190 to 220 degrees Celsius, plus it doesn’t usually require a heated 3D printing bed.
Other material qualities that make polylactic acid 3D printing possible include the excellent layer adhesion of the plastic, which makes it easy to build parts a layer at a time, as well as its availability in different colors.
Polylactic Acid in Textiles
Polylactic acid fabric is being used to make products such as upholstery, disposable gowns, and even fashion wear. It brings the advantage of eco-friendliness to the textile industry, among other advantages. PLA clothing is also comfortably soft and great in controlling moisture.
PLA fabric may also be combined with other polymers to improve its strength, or blended with other clothing materials such as cotton or wool. Note that polylactic acid fibers are used as woven or non-woven.
Woven polylactic acid fibers can be used for pillows, duvets and others, while non-woven fibers are applied in women hygiene products, wipes, and similar products.
Polylactic Acid in Agriculture
Being a biogradable plastic, polylactic acid will decompose in the soil over time. This and other properties have seen it being used in agricultural applications. Farmers often use it as bio mulch or netting to control weeds and evaporation, or as a pest barrier.
Other uses of polylactic acid in agriculture include trays, pots and other containers for seedlings. In addition to being biodegradable, PLA offers the advantage of being no-toxic when used in agricultural activities.
Polylactic Acid in Construction
In the construction industry, polylactic acid plastic presents an environmentally friendly material for sustainable buildings and other structures. So it’s being used for insulation and partitioning needs, providing thermal benefits while also reducing the use of other materials that are not as eco-friendly.
The use of PLA in construction presents these benefits overall: biodegradability, lower carbon footprint, compatibility with different construction materials, and as an economical construction material depending on the application.
Polylactic acid is a versatile type of thermoplastic that finds use in virtually every sector, from medical and packaging to textiles and 3D printing. Its many advantages make is a viable option in many applications. These include its synthesis from renewable resources, biodegradability, and unique material properties.