New Bio-Composites Based on Polyhydroxyalkanoates and Posidonia oceanica Fibres for Applications in a Marine Environment

Abstract

Bio-composites based on polyhydroxyalkanoates (PHAs) and fibres of Posidonia oceanica (PO) were investigated to assess their processability by extrusion, mechanical properties, and potential biodegradability in a natural marine environment. PHAs were successfully compounded with PO fibres up to 20 wt % while, at 30 wt % of fibres, the addition of 10 wt % of polyethylene glycol (PEG 400) was necessary to improve their processability. Thermal, rheological, mechanical, and morphological characterizations of the developed composites were conducted and the degradation of composite films in a natural marine habitat was evaluated in a mesocosm by weight loss measure during an incubation period of six months. The addition of PO fibres led to an increase in stiffness of the composites with tensile modulus values about 80% higher for composites with 30 wt % fibre (2.3 GPa) compared to unfilled material (1.24 GPa). Furthermore, the impact energy markedly increased with the addition of the PO fibres, from 1.63 (unfilled material) to 3.8 kJ/m2 for the composites with 30 wt % PO. The rate of degradation was markedly influenced by seawater temperature and significantly promoted by the presence of PO fibres leading to the total degradation of the film with 30 wt % PO in less than six months. The obtained results showed that the developed composites can be suitable to manufacture items usable in marine environments, for example, in natural engineering interventions, and represent an interesting valorisation of the PO fibrous wastes accumulated in large amounts on coastal beaches.

Novel Sustainable Composites Based on Poly(hydroxybutyrate-co-hydroxyvalerate) and Seagrass Beach-CAST Fibers: Performance and Degradability in Marine Environments

“…As shown, up to 20 wt % of PO fibers (PCA20), the effect of the fibers resulted in being compensated by the increase of the weight plasticizer/PHBV ratio going from the PCA (ATBC/PHBV = 0.11) to the PCA20 (0.15); while for PCA30 (with 30 wt % PO fibers), the high presence of fibers led to an inevitable reduction of the tensile properties despite the higher ATBC/PHBV ratio (0.175). These results are in accordance with those of other authors [ 24 , 27 , 28 ] relating to composites containing Posidonia oceanica fibers. The observed behavior is typical of particle-filled polymeric matrices with poor or no compatibility between the components, meaning that stress transfer phenomena cannot occur and the filler particle becomes a stress concentrator leading to brittle fracture [ 40 , 41 ].…”

“…In some cases, the developed composites showed promising mechanical and physical properties. Recently, the fibrous wastes derived from a seagrass, Posidonia oceanica (PO), have also been used as filler in the production of “green” composites [ 23 , 24 , 25 , 26 , 27 ], including PHA-based composites [ 28 ]. Posidonia oceanica is a Mediterranean endemic species that covers 60% of the seabed from 0 to 40 m depth [ 29 ].…”

Effect of Almond Shell Waste on Physicochemical Properties of Polyester-Based Biocomposites

“…This behavior was related to the higher amount of ASP incorporated and its degradation over this temperature range. According to other authors, cellulose, hemicelluloses and lignin show a broad temperature range starting at about 250 • C and ending at 450 • C in a progressive weight loss process, and this degradation can reduce the thermal stability of biopolyesters [43][44][45]. Similar findings were reported by Liminana et al [31] who observed a decrease of 11.2 • C in thermal stability of PBS with the addition of 30 wt % of almond shells.…”

Manufacturing and Characterization of Composite Fibreboards with Posidonia oceanica Wastes with an Environmentally-Friendly Binder from Epoxy Resin

“…It is worth mentioning the work of Cocozza et al which reports the alternative use of PO wastes as a compost material or for energy recovery [ 35 ]. PO wastes have been used as a reinforcement into several polymer matrices such as polyethylene [ 36 , 37 ], polyhydroxyalkanoates (PHAs) [ 38 ], processed by extrusion with PO contents up to 40 wt %. With regard to the use of PO in particleboards, Maciá et al have recently reported the partial substitution of pinewood by PO in particleboards with polyurethane binders with interesting applications in the building industry [ 39 ].…”