Design of Polyhydroxyalkanoate (PHA) Microbeads with Tunable Functional Properties and High Biodegradability in Seawater

Abstract

Commercial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) and poly(3hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) were used to prepare microbeads, with diameter ranging from 50 to 100 µm, by an emulsion-evaporation process. The properties of the beads reveal that the elaboration process enables the formation of spherical particles, that the crystallinity of the former polymer is not altered during the process and that the surface roughness of the particles can be tuned by changing the nature of the lateral chain in the PHA structure, in good correlation with its crystalline behavior. The mechanical properties of the different PHA beads are also found to be intimely linked with the crystalline content of the beads, with modulus varying between 1 to 7 GPa. All these properties are also governing the degradation behavior of these materials, as tested under marine environment. With a rapid degradation, similar to cellulose, and a degradation rate correlated with the crystalline content, these results emphasize the interest in developing PHA materials with tunable functions and degradation properties.

Seawater-degradable, tough, and fully bio-derived nonwoven polyester fibres reinforced with mechanically defibrated cellulose nanofibres

“…Regarding biodegradability, PHBH has been reported to be degraded by Alteromonadaceae in seawater. 48 Volant et al reported that PHBH microbeads enclosed in a container with seawater and sand degraded by 80% in 250 d. 49 Sashiwa et al found that PHBH powder degraded by 31% in 28 d. 5 The film fabricated in the present study degraded by 50% in 14–40 d in a natural environment, which is comparable to the degradation behaviour observed in previous studies. 5 In contrast, more than 50% of the fibre sheets degraded in 7–10 d and almost completely degraded within ∼2 weeks.…”

Discussion about suitable applications for biodegradable plastics regarding their sources, uses and end of life

“…Alternatively, the use of nonbiodegradable nets that one would equip with captors and systematically retrieve from the marine environment might be just as efficient (Fjelstad, 1988;McElwee et al 2012). Other examples include the plastic particles and water-soluble polymers used in care products (e.g., cosmetics, detergents) (Sahlan et al 2020;Volant et al 2021), or the microfibers used in textiles (Fig. 1).…”

Carbon Recycling of High Value Bioplastics: A Route to a Zero-Waste Future

“…Bio-sourced and biodegradable polymers such as poly(lactic acid) (PLA), poly(hydroxy-alkanoates) (PHAs), and thermoplastic starch (TPS) offer a route to achieving this goal [ 35 ]. These materials are a class of polymers with properties such as stiffness, ductility, and elasticity which can be tuned to suit different applications [ 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. As such, they have the potential to replace a wide range of conventional polyolefins [ 43 ].…”