Biopolymers, green shoots grow strong
The world of plastics is also committed to meeting the ecological challenge of the years to come. Innovations in plant-based plastics are flourishing, some of which certainly foreshadow the plastics of the future. Let's take a closer look!
PLA takes its place
Polylactic acid (PLA) is one of the oldest bioplastics, which explains, at least in part, why it is now the undisputed star among plant-based plastics. PLA accounted for almost 20% of all bioplastics produced in 2021.
Its manufacturing process is based on lactic acid obtained by fermenting sugars (sucrose, glucose, etc.) present in plants (sugar cane, beet, etc.) or extracted from their starch (corn, wheat, potatoes, etc.). The lactic acid is then distilled and polymerised to become polylactic acid. It is compostable under industrial composting conditions (above 60°).
PLA is the star of biosourced plastics and is widely used in food packaging and 3D printers.
PLA is mainly used in food packaging (66% of its production), particularly for its barrier properties (protection against oxidation) and because its transparency allows consumers to see the food. It is very flexible and can be made more rigid by adding lime, in which case it is known as crystallised PLA. It is also used to make trays, food films, glasses and cups. Cutlery and cup lids are more often made of crystallised PLA.
This packaging is mainly used in the fast-food industry for foods with a short shelf life.
This makes sense since the polymer is not perfectly waterproof, which prevents it from being used to protect long shelf-life products. It has also made a place for itself in the world of non-woven fabrics (wipes, nappy covers, etc.) and materials used in 3D printers, particularly because its melting point is lower than that of other polymers. It is thus the main material used to make many 3D-printed prostheses. It is also used in the surgical field to manufacture certain sutures, and the possibility of using it in stents is currently being studied. PLA is perfectly recyclable, but the collection channels have yet to be developed.
PHA in search of a future
Polyhydroxyalkanoates (PHA) and polyhydroxybutyrate (PHB) have similar manufacturing techniques and are, according to the experts, promised to have a very bright future despite their high cost at the current time. These plant-based polyesters have the advantage over PLA of being biodegradable in the natural environment. They could therefore be of great use in the health sector for designing resorbable materials: sutures, capsules of active substances, etc.
Rislan ®: going from strength to strength
In 1947, Arkema launched Rislan ®, a new castor oil-based polymer. It was a polyamide 11 that competed with the famous nylon developed by the American company Dupont de Nemours. Its career highlights are remarkable.
Recognised for its strength, it is used in cables, high-pressure hoses, etc. It has even become a generic name, since DIYers in France generally call plastic clamping collars a "rilsan", after the material they are made of, of course. What is even more extraordinary is that this material, which is one of the "ancestors" of modern biosourced plastics, has managed to renew itself to become one of the most sought-after polymers.
Arkema has turned this polymer into a thermoplastic elastomer called Pebax®. Lightweight, elastic and shock-resistant, it can be found in the soles of sports shoes and ski boots. For the record, Usain Bolt, the triple medal-winning runner at the 2016 Rio Olympics, wore shoes fitted with Pebax® soles, in green to match his shirt. Needless to say, Arkema shared in the triumph of his victories.
Rislan ® has earned its credentials by helping many athletes to win their Olympic titles.
Biopolyethylene keeps it sweet
Polyethylene (PE) is the most widely used plastic in the world. Inexpensive to produce, versatile and particularly resistant, it is used in all industrial sectors: packaging, construction, automotive, etc.
It is traditionally produced from fossil resources, by polymerisation of ethylene. Ethylene, the basic building block of the material, can also be obtained from the ethanol produced by the fermentation of sugar-rich plants (such as sugar cane, corn, etc.).
Sugar cane production has the advantage of being less damaging to the environment than that of sugar beet or maize, which requires more resources and water. The only drawback is that the production cost of bioPE is more expensive than that of petroleum-based PE. That said, various studies show that end consumers are willing to pay a little more for their products if they are of sustainable origin.
With the need to decarbonise, toy manufacturers are taking a keen interest in biosourced plastics.
Toy giant Mattel recently announced that it would make all of its products from biosourced or recycled polymers by 2030.
The first toy to be made from biosourced polyethylene will be its iconic Rock-a-Stack which was initially launched in the 1960s.
Lego, the toy industry’s other heavyweight, has been saying for some years that it wants to replace the ABS in its famous bricks with a "green polymer".
In the meantime, it has opted for bioPE for all the botanical elements in its sets (tree leaves, bushes and tree trunks).
However, those parts only account for 2.2% of the parts that the company produces. For the moment, the famous bricks are not made of bioPE because it does not offer the same properties (shine, strength, non-deformability, etc.) as the ABS that is currently used in their composition, making them almost indestructible and perfectly safe for use by children.
A sly nod to the material used? The leaves on the trees of Lego products are now made of bioPE, a biosourced polyethylene.
BioPET has a lot of bottle
Sugar cane is also a favourite of manufacturers of biosourced polyethylene terephthalate (PET). Until recently, this PET was only partially biobased. It was made from petroleum-based terephthalic acid which is identical to the ethylene glycol usually derived from sugar cane. As a reminder, PET is the most widely used material for making beverage bottles. Moreover, it is a polymer that is highly recyclable.
BioPET has been a huge success in recent years thanks to Coca-Cola, which launched its first bioPET bottles in the late 2000s (the latter still containing petroleum-based terephthalic acid). The brand set itself the goal of producing bottles from 100% plant-based terephthalic acid within a decade. This was achieved through its partnership with the American company Virent, a start-up specialising in biofuels. The PlantBottle, their 100% biosourced bottle, is made from a plant-derived paraxylene that has been converted into terephthalic acid.
This is a world first that is expected to be emulated by its many competitors. In Europe and Japan, Coca Cola hopes to stop using fossil-based PET by 2030. In these countries, the bottle of the future could be made up of 70% of mechanically-recycled PET with the remainder being bioPET.
Coca-Cola is the first brand to bring a fully biosourced bottle to market.
PVC gets a pinch of salt
Polyvinyl chloride (PVC) is also one of the most widely used polymers in the world. It has long been a staple in the construction industry, where it is used in pipes, windows, doors, electrical cables, cladding, etc.
Two raw materials are needed to produce PVC: sodium chloride (from sea or cooking salt) and ethylene. Producing green ethylene from plants is no longer what you might call a novelty.
What is, however, is creating it from paper pulp residues or used cooking oil extract, at least in the case of PVC. Aliaxis, one of the world's leading pipe manufacturers, now offers a range of pipes made up of 80% of bio-attributed* PVC, supplemented by 20% of recycled PVC. The remaining 30% is made up of mineral fillers to ensure acoustic performance.Of course, these pipes have the same technical properties as traditional PVC pipes.
* Bio-attributed : Bio-based PVC is 100% non-fossil based. Bio-attributed PVC allows the blending of a small proportion of fossil material, based on the principle of mass balance, consisting of frying oil residues and paper pulp
Biosourced PVC is derived from paper pulp residue or used cooking oil.