The purpose of this article is to give some insights on the facts, perceptions, advantages and disadvantages of PLA or Polylactic Acid.
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PLA or Polylactic Acid
PLA was discovered in 1932. It’s a compostable and bio based polyester.
The first applications of PLA were in the biomedical sector. PLA has an ability to be absorbed biologically. It takes between 6 months to 2 years to break down inside body. Development in production methods and capacity made PLA cheaper & enabled wider applications such as packaging material.
The world production of PLA is around 240 K tonnes / year. NatureWorks (ingeo) is a joint-venture between Cargill & PTT and produces around 135 K tonnes / Year. Total-corbion (luminy) is a joint venture between Total & Corbion and produces around 75.000 K Tonnes per year.
TECHNICAL
PLA is a thermoplastic; it will become liquid at melting point of 150 to 160 Celsius.
PLA can be processed via extrusion, injection molding, casting, blown film, thermoforming, and fiber spinning.
PLA is made by the polymerisation of lactic acid or lactide.
Lactic acid is produced through bacterial fermentation of a carbohydrate /sugars coming from plants such as corn, sugar cane, sugar beet, cassava
When the plants are grown specifically for the production of PLA, we’ll refer to it as 1st generation PLA.
When we use residue, waste and by-products such as stems, straw, husks, and leaves as long as they contain carbohydrate, we’ll refer to it as 2nd generation PLA.
First generation PLA is more more efficient in terms of production but less ethically correct than the second generation..
Advantages
Production
- PLA is made from renewable raw materials.
- It has a reduced carbon footprint compared to fossil based plastics. two reasons:
- crops absorb co2 when growing;
- It takes less energy and this produces less greenhouse gas to produce PLA than fossil-based plastic
- PLA is made in the USA (NatureWorks Ingeo)
Material
- PLA melts more easily because it has a lower melting point than many fossil-based plastics. It’s easy to work with PLA and it requires less energy to transform.
- One of the two most used plastics in 3D printing (45% market share). It has a low melting point, inexpensive, easy-to print, no fumes. It’s the best option in case of 3D printing.
End-of-life
- PLA is compostable
- When PLA is Incinerated, it emits less toxic fumes than oil based plastics
- Food Contamination of food packaging is not a problem, unlike with plastic recycling.
- In case of biomedical use, PLA degrades into non-toxic acid.
Disadvantages
Production
- Price – PLA is more expensive than fossil based plastics
- 1st generation uses food crops
- When using crops to produce plastics; one should beware of Intensive agricultural practices, over using fertilisers and GMO, mono cultures and the destruction of natural habitats.
End of Life
- Compostable
- It doesn’t compost fast enough for industrial composters.
- The residue is not compost. it doesn’t improve the quality of soil. No nutrient.
- It changes the PH value of the soil. It makes it more acidic.
- Recyclable – PLA has a lower melting point and cannot be recycled with other plastics. There’s not enough PLA and it’s too dispersed to make recycling economically viable.
Material
- Low melting point makes PLA unsuitable for high temperature applications. PLA may even show signs of getting soft or deforming on a hot summer day.
- PLA has a higher permeability than other plastics. Moisture and oxygen will go through it more easily than other plastics. This will result in faster food spoilage. PLA is not recommended for long-term food storage applications.
- PLA is not the hardest or toughest plastic. PLA is not suitable for applications where toughness and impact resistance are critical.