Foreword: what is PHA?
PHA is part of a growing ecosystem of biomaterials designed to reduce our dependence on petroleum-based plastics. As a polymer derived from natural sources, PHA contributes to a circular economy, offering a sustainable alternative to conventional plastics. In combination with other bioplastics (such as PLA) and biosourced composites, PHA supports an overall ecological approach. This means reducing waste and minimising environmental impact in all sectors of activity.
Bioplastics: why is PHA king?
Its biodegradability is what sets it apart. This natural polymer, produced by microorganisms, is 100% biosourced and 100% compostable. It decomposes naturally in an environment, leaving no trace behind. PHAs offer a sustainable alternative to petroleum-based plastics, and can be manufactured in large volumes. they’ve come just at the right time to help manufacturers make an ecological transition.
How is PHA made?
PHA production is based on a fermentation process. It involves specific microorganisms capable of synthesising these polymers under certain conditions. These bacteria set up a survival mechanism when they are subjected to nutrient stress. In other words, this defensive reflex produces matter: PHA. In the form of microscopic inclusions (granules), the micro-organisms store up energy, all that remains is to harvest them.
What are the different types of PHA?
There are 8 different types of PHA, each with its own scientific name, based on its composition, properties and applications. Biosourced, biodegradable and biocompatible, they are used in a wide range of applications. Let’s get to the heart of the matter.
1st type of PHA: PHB (Polyhydroxybutyrate)
Composed solely of 3-hydroxybutyrate monomers, PHB has a rigid, brittle structure. Its properties are similar to those of polypropylene, but it is more brittle and less resistant to impact. PHB is commonly used to produce packaging, protective films and for certain medical applications (biodegradable sutures).
2nd type of PHA: PHBV (Polyhydroxybutyrate-co-valerate)
With a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate, PHBV is stronger and more flexible than its predecessor. Due to its lower melting temperature and the presence of 3-hydroxyvalerate, its ductility is improved and its crystallinity reduced. PHBV also has good resistance to oils, greases and solvents, making it useful for food packaging and industrial applications.
3rd type of PHA: P3HB4HB (Poly-3-hydroxybutyrate-co-4-hydroxybutyrate)
Thanks to its composition, P3HB4HB has increased elasticity and remains the most flexible of the PHAs. It has good tensile strength and impact resistance. P3HB4HB has applications in a wide range of fields, including packaging, agriculture, consumer goods and medicine:
- temporary implants
- biodegradable sutures
- drug delivery devices
- tissue engineering
4th type of PHA: PHBH (Polyhydroxybutyrate-co-hexanoate)
It offers greater flexibility and impact resistance, as well as rapid degradation in the marine environment. PHBH is also frequently used in marine applications because of its rapid biodegradability in salt water. It can be transformed by conventional industrial processes such as injection moulding, extrusion and thermoforming.
5th type of PHA: PHO (Polyhydroxyoctanoate)
This PHA is highly elastic and shock-resistant. PHO is therefore suitable for flexible applications in industry such as:
- elastic materials
- food films
- adhesives
- 3D printing components
6th type of PHA: P4HB (Poly(4-hydroxybutyrate))
This polymer is also resistant to hydrolysis and enzymatic degradation. With good thermal stability and enhanced chemical resistance, it is used for applications in biological environments. However, the main challenge with P4HB lies in its high production costs (due to the complexity of its biosynthesis).
7th type of PHA: PHBHep (Poly(3-hydroxybutyrate-co-3-hydroxyheptanoate))
This PHA offers a good combination of flexibility, impact resistance and ease of heat treatment. It offers good barrier properties against gases and moisture, ideal for food and agri-food applications such as:
- biodegradable mulching films
- seed containers
- packaging materials (bags, pouches, etc.)
- disposable utensils and crockery (PHA straws, cups, cutlery, etc.)
- applications in the food industry
8th type of PHA: PHBHN (Poly(3-hydroxybutyrate-co-3-hydroxynonanoate))
Compared with other PHAs, PHBHN improves flexibility and its thermal properties give it greater mechanical strength. It is used, for example, to make disposable utensils (crockery) and toys. Because of its biocompatible nature, health and safety are not compromised.
Whatever the type of PHA, these bioplastic products represent a promising ecological alternative to conventional plastics. Both biodegradable and biocompatible, they represent the future of industry across a wide range of sectors. Resistant, flexible or supple: which will you choose?
