In 1930, American chemist Wallace Carothers, known for the research and development of Neoprene and Nylon in a chemical company named Dupont, invented PLA plastic. Commercial production of PLA plastics began in 1980 by an American company Cargill.
What are PLA Bioplastics?
Polylactic acid plastic, also named PLA plastic, is a type of polymer derived from renewable sources like tapioca roots, cornstarch and sugarcane. Its properties are similar to synthetic plastic, and it is eco-friendly. Hence it entered the plastic industry as a competitive commodity.
How are PLA bioplastics made?
Polylactic plastic is made by fermenting carbohydrate sources like sugarcane, maize or corn starch under controlled conditions. The building blocks of PLA plastic, which is lactide monomer or lactic acid, are later polymerized into PLA.
In the beginning, the starch gets separated when sugarcane goes through wet milling. Afterwards, it gets mixed with enzymes or acid and then it is heated. The heating procedure converts starch into corn sugar or Dextrose. Finally, the derived sugar produces L- Lactic acid, the fundamental component of PLA plastic.
Types of PLA bioplastics
There are many types of PLA plastics, but few important ones are regular Poly L-lactide (PLLA), racemic Poly L-lactic Acid (PLLA), Poly DL- Lactic Acid (PDLLA) and Poly D-lactic Acid (PLDA).
Though all the types of PLA plastics are made up of the same renewable source – lactic acid, the orientation of atoms are different in these types. Also, the physical and chemical properties slightly vary in all of them.
Uses of PLA bioplastics
PLA bioplastic has a wide range of applications in various sectors like textiles, packaging, medical, cosmetics and so on. Some of the uses of PLA plastic are:
Since PLA bioplastics are biodegradable and biocompatible, it has vital importance in the medical industry. The healthcare industry uses polylactic acid plastic in manufacturing tissue engineering stages and bone fixation devices like plates, screws, rods, pins, surgical equipment and meshes.
Its adaptability with minimum infection and inflammation has membrane applications like covering wounds and making stitches plastic.
Besides, PLA plastics are also used to deliver medical materials, medical implants and are used in various dermatological procedures like scar rejuvenation and facial lipoatrophy.
In the textiles and apparel industry, efforts have been made to replace synthetic polyester textiles with renewable textiles. Due to its lightweight, recyclability, good resistance to sun rays, and breathability, PLA plastic is used to make carpets, beddings, shirts and sportswear.
Since PLA plastic has low smoke generation characteristics, it is also used to manufacture insulating materials, garbage bags, and protective foams.
As a result of consumer awareness regarding synthetic plastic pollution, cosmetic industries are now shifting towards PLA biodegradable plastics. Products like cotton buds, razors, hairbrushes, toothbrushes and diapers are made using polylactic acid plastics.
Packaging and disposable
PLA bioplastics are typically safe for packaging food, and it is also approved by the Food and Drug Administration (FDA). Though it can discharge lactic acid when it comes in contact with certain liquids, its concentration does not harm humans.
In the form of rigid thermoforms, PLA bioplastic is used to manufacture yoghurt pots, meat trays, bakery, herbs and candy containers, coffee lids, cold drink cups, fruit and vegetable clamshells. In the bottling sector, it is used to make milk bottles with a short shelf life, edible oil bottles and mineral water bottles.
As films, it is used as a wrap for flowers and candy twists, making lamination films, display carton windows, tapes, bread bags, cake mix pouches, die-cut labels, and envelopes.
Due to its durability, high heat resistance and hydrolytic stability, biobased PLA plastic is used in making structures for electrical and electronic appliances.
It has significant use in the automobile industry and is used for manufacturing high-end cars’ wheel covers, translucent roofs, under the hood parts and safety helmets.
PLA bioplastics are also suitable for making pillow covers, floor mats, door trims, ceiling material and front panels due to their superior tensile strength.
Advantages of PLA Bioplastics
PLA plastic has many benefits as compared to competing polymers, and that’s why manufacturers prefer it. Some of them are:
- PLA plastics are derived from biomass, thus it is biodegradable and more environmentally friendly.
- As compared to other plastic production, PLA plastics require less energy to produce.
- When polylactic plastic degrades, it transforms into natural materials like carbon-di-oxide, water which reduces plastic waste.
- Since PLA is a thermoplastic, it can be melted, recycled and reshaped without changing its chemical properties.
- It is carbon neutral, which means it doesn’t emit carbon dioxide into the atmosphere when recycled.
- PLA is non-toxic, that’s why it is used in the food packaging and medical industry.
- When oxygenated, it does not produce any toxic fumes as synthetic plastics do.
- It has a smoother, shinier and glossy appearance; hence it is used in textiles and automobile industries.
- PLA plastics emit a sweet smell in the printing process and can easily be printed even on a cold surface.
- As compared to other bioplastics like polyhydroxyalkanoate (PHA), poly γ-caprolactone (PCL) and polyethylene glycol (PEG), it has better thermal manufacturability.
Disadvantages of PLA Bioplastics
Though PLA plastics have many applications and unique properties it also has some disadvantages like:
- If PLA plastics do not get the ideal temperature and pressure, it does not degrade and takes around 100 to 1000 years to decay.
- As compared with other bioplastics, PLA has a lower glass transition temperature of 55 degree Celsius.
- Unless mixing PLA with other polymers, it is primarily more brittle and ductile.
- PLA bioplastics also have a lower crystallization rate and strength as compared to petroleum-based plastics.
- Mixing PLA bioplastics with synthetic plastic could contaminate the recycling procedure as it has different chemical properties. Hence, during the recycling process, it should be separated from traditional plastic.
- It is thermally unstable and also has poor gas barrier characteristics.
- It has a high production cost.
Properties of PLA Plastics
Due to its similar properties as petroleum-based plastics, PLA plastic is a great biodegradable alternative. Some of the characteristics of Polylactic acid plastics are:
The thermal properties of PLA bioplastic usually depend upon its molecular weight, thus, it is classified as a semi-crystalline polymer. It has a high melting point of 180 degree Celsius but a low glass transition temperature of 55 degree Celsius.
It is ultraviolet rays resistant and has low smoke formation and flammability during its production.
PLA plastics have high mechanical strength and resistance with a good appearance compared to other polymers like polyurethane, polystyrene and polypropylene.
The tensile strength, flexural strength and ‘Elongation at break’ of PLA plastics are also better than other bioplastics.
PLA bioplastic is non-Newtonian fluid and pseudoplastic, which means the change of viscosity depends upon the stress applied to it. Also, when tension is applied to it, its viscosity decreases.
Is PLA plastic sustainable?
In a broader sense, PLA plastics are sustainable as it comes from renewable sources. However, PLA plastics require precise temperature and pressure to degrade.
In the degradation process of PLA plastic first, it needs to be heated at 60 degree Celsius. Then it should be exposed to particular microorganisms which digest the plastic and decompose it.
Secondly, PLA plastics need to be sorted out when recycling as they can’t be recycled with other plastics due to their different chemical properties. This increases the cost of transportation for bioplastic companies.
The current commercial market of PLA plastics
The demand and supply for bioplastics are increasing as people want to use more environmentally friendly plastics. PLA plastics has a significant share in the bioplastic market, and its production requires 10.3 % of raw materials needed by bioplastic production.
The leading manufacturing companies of PLA plastics are Nature works, Total Corbion PLA, Evonik, Pyramid technologies, WeforYou and Synbra.
The top exporter of PLA bioplastic is the United States of America, followed by the Netherlands and China. The largest importer of Polylactic acid plastic is Taiwan, followed by Netherlands and Germany.
Growing environmental concerns, health and safety, and reducing carbon emissions are the few factors responsible for bioplastic usage. There are several bioplastics today, but due to the versatility and sustainability of PLA plastics, it has unlimited applications.