aced with the environmental crisis caused by non-biodegradable plastics, PHAs are emerging as an innovative ecological solution. But what are they? How are they manufactured? What can they replace? Why should companies use them? Let us decipher the secrets of these biosourced plastics.
Foreword on PHA biopolymers
What is PHA?
The production of PHA is based on a fermentation process. It involves specific microorganisms capable of synthesising these polymers under certain conditions. PHA (Polyhydroxyalkanoate) is produced by certain bacteria under nutrient stress. They produce it as part of a defensive reflex to store energy. It is therefore, by definition, biosourced, since the raw materials are considered renewable. It is grown from sugar, vegetable oils and other biomasses.
PHA: the 5 stages of industrial production
- supply and multiplication of microorganisms in a fermentation reactor
- the microorganisms react to the nitrogen (or phosphorus) limitation and begin to accumulate PHA granules inside their cells
- harvesting and extraction of the polymer from the microorganism cells (their cell walls are then broken to extract the PHA)
- purification of the raw PHA to make a clean material that can be used by the plastics industry
- transformation of PHA granules by moulding, extrusion or other conventional processes.
Bioplastics: what are the different types of PHA?
Bioplastics belong to a family of polymers that includes various PHA subtypes. Each of these polymers has its own specific characteristics, and each is suited to different industrial applications. PHAs therefore offer a wide range of adjustable properties thanks to the diversity of the monomers that make them up. In other words, these biopolymers are versatile and hold great promise for the future of sustainable materials.
- PHB: composed solely of 3-hydroxybutyrate monomers, it is rigid and brittle, with a melting temperature of around 175°C. Its properties are similar to those of polypropylene, but it has low impact resistance.
- PHBV: is a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate, more flexible and resistant than PHB. With a lower melting temperature (around 145°C), the presence of 3-hydroxyvalerate improves ductility and reduces crystallinity.
- P(3HB-co-4HB): this polymer is highly flexible and has greater elasticity than other PHAs. This bioplastic has good tensile strength and impact resistance.
- PHBH: offers greater flexibility and impact resistance, as well as rapid degradation in the marine environment.
- P(3HB-co-3HO): this polymer is highly elastic and impact-resistant, with a very low glass transition temperature, making it suitable for flexible applications.
- P4HB: with a structure composed of 4-hydroxybutyrate monomers, it has excellent biocompatibility and biodegradability. This polymer is also resistant to hydrolysis and enzymatic degradation.
- PHBHep: the perfect combination of flexibility and impact resistance.
- PHBHN: thanks to its thermal properties, it offers good mechanical resistance compared with other PHAs.
Why is PHA the future of the bioplastics industry?
PHA biopolymer: an environmentally-friendly, biodegradable plastic
This bioplastic stands out thanks to its ability to degrade in various environments. Whether in soil or water, it represents an environmentally-friendly alternative to conventional plastics. To be certified compostable, a product must comply with specific standards.
N.B. Since 2021, various laws in France have banned the use of single-use plastics. Bioplastics help to limit our waste. Obligation or reason?
What are the industrial applications of PHA biopolymers?
- Biodegradable bags, packaging films, household items, crockery, etc.
- Medical sutures and materials for absorbable medical devices
- Coating materials for capsules and transdermal patches
- Food packaging, PHA agricultural products and marine applications
- Elastic materials, adhesives and components for 3D printing
Technical properties and environmental benefits of PHA
PHA: a renewable, biodegradable and compostable raw material
We must learn to produce responsibly without leaving anything behind. Unlike petrochemical plastics, PHAs are produced using renewable raw materials. This helps to reduce the overall carbon footprint and also avoids drawing on natural resources. Whether in compost, soil or even seawater, PHA will disappear. This distinguishes it from its cousins, where micro-particles can persist for centuries.
A biosourced plastic synonymous with plurality and safety
This material, which is non-toxic to humans, can be used for both food and medical applications. As demonstrated earlier, PHAs can have a variety of properties. Depending on the strain, this polymer can be rigid and resistant, but also flexible and elastic. This material can thus be adapted to a number of uses, and it is this mechanical variability that is of interest to industry.
PHA biopolymers represent a major innovation in the fight against plastic pollution. Because they are biosourced, biodegradable and biocompatible, they are ideal candidates for replacing (almost all) materials. And because they have so many applications, we can use them over and over again.This green revolution is good for the planet!
