Microplastics have become one of the greatest environmental challenges worldwide. To turn this dramatic damage around, EU regulators now want to ensure that plastic itself is fully recyclable or biodegradable. The aim of the present work is to develop a biobased and biodegradable biocomposite based on commercial polyhydroxyalkanoates (PHAs) and nanoclays, with the objective of achieving a reduction of rancid odour while avoiding any loss in thermomechanical properties, thus tackling two key disadvantages of PHAs. This research aims at completely characterising the structural, thermal and mechanical behaviour of the formulations developed, understanding the compatibility mechanisms in order to be able to assess the best commercial combinations for industrial applications in the packaging and automotive sectors. We report the development of nine nanobiocomposite materials based on three types of commercial PHA matrices: a linear poly(3-hydroxybutyrate) (P3HB); two copolymers based on poly(3-hydroxybutyrate)-co-poly(4-hydroxybutyrate) (P3HB-co-P4HB); and nanoclays, which represent a different polar behaviour. Dispersion achieved is highly relevant compared with literature results. Our findings show impressive mechanical enhancements, in particular for P3HB reinforced with sepiolite modified via aminosilanes.

The aim of this research paper is to study the behaviour of a common used biopolymer (Poly(Lactic Acid) (PLA)) after several reprocesses and how two different types of additives (a melt strength enhancer and a nanoadditive) affect its mechanical and rheological properties. Systematic extraction of extrudate samples from a twin-screw compounder was done in order to study the effect in the properties of the reprocessed material. Detailed rheological tests on a capillary rheometer as well as mechanical studies on a universal tensile machine after preparation of injected specimens were carried out. Results evidenced that PLA and reinforced PLA materials can be reprocessed and recycled without a remarkable loss in their mechanical properties. Several processing restrictions and specific phenomena were identified and are explained in the present manuscript.

Bags used to protect and accelerate the ripening of bananas are a clear example of the environmental problem of packaging waste. Small pieces of these non-biodegradable bags are frequently disposed on the soil by accident (environmental conditions and poor handling during the harvest) and remain there for years. This work focuses on the development of protective biodegradable bags reinforced with banana fiber, obtained from waste of the banana plants, thus promoting a circular economy and a more environmentally friendly process. To achieve this, different bio-based composites were tested (processability) by compounding extrusion (biopolymer and banana fiber with different process steps) and blown film extrusion. The bags produced were tested in field and sequentially improved in three generations of biofilms. The results showed that the maximum processable fiber content was 5 wt %. Additionally, the micronizing of the compounds was crucial to simplify the blown film extrusion and improve the smoothness of the bags (scratches avoidance on the banana surface). The final bags (Mater-Bi biopolymer, 5% combed and sieved banana fiber, and 2.5 wt % TiO₂ for ultraviolet light filtration), performed better than the conventional ones (faster maturing, i.e., earlier harvest, and easier handling) and fulfilled the biodegradability, composting and ecotoxicity test requirements.

Polyhydroxyalkanoates (PHAs) are nowadays considered competent candidates to replace traditional plastics in several market sectors. However, commercial PHA materials exhibit unsatisfactory smells that can negatively affect the quality of the final product. The cause of this typical rancid odour is attributed to oxidized cell membrane glycolipids, coming from Gram-negative production strains, which remain frequently attached to PHAs granules after the extraction stage. The aim of this research is the development of customised PHA bio-nano-composites for industrial applications containing organomodified nanoclays with high adsorbance properties able to capture volatile compounds responsible for the displeasing fragrance. To this end, a methodology for the detection and identification of the key volatiles released due to oxidative degradation of PHAs has been established using a headspace solid-phase microextraction technique. We report the development of nine bio-nano-composite materials based on three types of commercial PHA matrices loaded with three species of nanoclays which represent a different polar behaviour. It has been demonstrated that although the reached outcoming effect depends on the volatile nature, natural sepiolite might result in the most versatile candidate for any the PHA matrices selected.

Biopo-lybutylene succinate (bioPBS) is gaining attention in the biodegradable polymer market due to its promising properties, such as high biodegradability and processing versatility, representing a potential sustainable replacement for fossil-based commodities. However, there is still a need to enhance its properties for certain applications, with aesthetical and mechanical properties being a challenge. The aim of the present work is to improve these properties by adding selected additives that will confer bioPBS with comparable properties to that of current counterparts such as polypropylene (PP) for specific applications in the automotive and household appliances sectors. A total of thirteen materials have been studied and compared, being twelve biocomposites containing combinations of three different additives: a commercial red colorant, itaconic acid (IA) to enhance color fixation and zirconia (ZrO₂) nanoparticles to maintain at least native PBS mechanical properties. The results show that the combination of IA and the coloring agent tends to slightly yellowish the blend due to the absorbance spectra of IA and also to modify the gloss due to the formation of IA nanocrystals that affects light scattering. In addition, for low amounts of IA (4 wt %), Young’s Modulus seems to be kept while elongation at break is even raised. Unexpectedly, a strong aging affect was found after four weeks. IA increases the hydrophilic behavior of the samples and thus seems to accelerate the hydrolization of the matrix, which is accompanied by an accused disaggregation of phases and an overall softening and rigidization effect. The addition of low amounts of ZrO₂ (2 wt %) seems to provide the desired effect for hardening the surface while almost not affecting the other properties; however, higher amounts tends to form aggregates saturating the compounds. As a conclusion, IA might be a good candidate for color fixing in biobased polymers.