Did You Know what is PHA? – A plastic produced by bacteria!

Did You Know what is PHA? The Polyhydroxyalkanoates or PHAs are polyesters produced in nature by numerous microorganisms, including through bacterial fermentation of sugar or lipids. When produced by bacteria they serve as both a source of energy and as a carbon store. More than 150 different monomers can be combined within this family to give materials with extremely different properties.

PHAs are very attractive materials for three primary reasons: they can be created from renewable sources, they can also biodegrade, and they are biocompatible. To the first point, it is very exciting that scientists are finding ways to harvest and utilize material from sources like bacteria synthesis (PHA) and corn or sugarcane (other bioplastics). Previously, crops had to be diverted for the production of bioplastics, but in the last decade or so, there has been a focus on using waste materials (such as banana peels, potato peelings, etc) to produce bioplastics instead. By utilizing waste products, use of scarce resources can be maximized.

Biodegradability is the other key aspect that makes PHAs a very promising material. Environmental pollution is a hot topic with important implications; conventional petrochemical-based plastics have been at the very center of the controversy, primarily because they are so widespread and do not degrade easily. For instance, images of marine animals strangled by or ingesting various plastics show the stark reality of pollution. Of course, fossil-fuel based plastics have done much to improve the material lives of humans, but when it comes to pollution, new innovations in biodegradability are very welcome.

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Because PHAs are biocompatible (which means not harmful to living tissue), they can and have been utilized in a variety of medical and surgical applications. Looking forward, the potential also exists that PHAs will be involved in “wearable” internal technology applications.

In the 90´s, companies tried to market PHAs and failed. Companies developing the plastic have tried in vain for a long time to market it on the basis of its biodegradability. According to Jan Ravenstijn, a well-known consultant in the area of bioplastics, they neglected the laws of polymer marketing in doing so.

Biodegradable PHA bottles disintegrate in the soil within 2 months (but remain intact as long as they are not discarded). – https://www.biobasedpress.eu/2016/08/pha-promising-versatile-biodegradable/

In bioplastics marketing, quality and price come first; only if a PHA fulfils the necessary price/quality ratio requirements, biodegradability will lend an extra and strong sales argument.

PHAs are very easy to process. They can be blown and moulded, foamed and processed into yarns. They make excellent packaging materials, also for food packaging. They can be printed, sealed, painted. Mixing with other plastics will often improve the qualities of the latter. Because of its large variety, PHA can substitute almost all major plastics in many of their applications: polyethylene, polypropylene, polystyrene, PVC, PET. PHAs can be processed to glues. Some kinds of PHA can be used as implants, the material will be entirely resorbed by the body in the course of time. There seems to be just one impediment: price. This is too high yet for most applications.

What can producers do about that? Now, we can wait and see!

Characteristics of PHAs

  • Water insoluble and relatively resistant to hydrolytic degradation.
  • Good ultraviolet resistance but poor resistance to acids and bases.
  • Soluble in chloroform and other chlorinated hydrocarbons.
  • Biocompatible and hence suitable for medical applications.
  • Sinks in water, facilitating its anaerobic biodegradation in sediments.
  • Nontoxic.
  • Less ‘sticky’ than traditional polymers when melted.

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