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Microalgal biomasses, consisting of micronized Spirulina Platensis and its low protein fraction, were investigated in this work as possible renewable biofillers in natural rubber compounds, with the aim of replacing the commonly used carbon black. Natural rubber, in some cases blended with 10% of epoxidized natural rubber to improve the matrix-filler affinity, was compounded with 25, 35, 50 and 75 phr of each biomass. Compounds with 25, 35 and 50 phr of carbon black N990 were also prepared as benchmarks. After compounding, vulcanization times were determined by dynamic mechanical analysis. Rubbers were vulcanized by compression moulding and characterized by means of morphological analysis (scanning electron microscopy), thermal analysis (thermogravimetric analysis, dynamic mechanical thermal analysis) and mechanical tests (tensile tests, strain induced crystallization detection by X-ray diffraction, pure shear fracture tests). Microalgal biomass turned out to be homogeneously dispersed in natural rubber matrix and the materials obtained required lower curing times compared to carbon black compounds. It was found that, up to 50 phr, Spirulina has the ability to increase rubber tensile strength and modulus, acting similarly to N990, while decreasing rubber thermal stability and fracture toughness. [ABSTRACT FROM AUTHOR]

Hard, scratch-resistant and transparent fluoropolymer-based hybrid coatings are successfully prepared through the sol-gel chemistry and investigated, in the attempt to correlate the chemical, physical and surface properties of these materials with the mechanical properties (i.e. hardness and elastic modulus) measured at the nanoscale by atomic force microscopy (AFM). The organic component of these coatings consists in a hydroxyl-functional fluoropolymer resin, which belongs to the class of chlorotrifluoroethylene-vinylether copolymers and exhibits remarkable properties such as easy handling, great weather resistance, good adhesion and flexibility of coatings. A functionalization of this copolymer is also performed using an isocyanate-functionalized silane in order to assure a covalent cross-linking of organic fluorinated resin with inorganic phases. The combination of the silanized chlorotrifluoroethylene-vinylether copolymer with different sols composed of silica and zirconia is used to obtain high scratch resistance and high durability coatings on polycarbonate. A series of three hybrid coatings with different zirconia/silica molar ratios (0.09/0.48) are developed and analyzed by differential scanning calorimetry (DSC), water contact angle measurements, pencil hardness and adhesion tests. AFM scratch hardness, coating wettability and surface composition measured by Fourier transform infrared spectroscopy (FTIR) are regularly monitored over long-term UV–vis light exposure, to assess the durability of the hybrid coatings. Interestingly, the hybrid fluorinated coatings exhibit an improved scratch resistance and a superior long-term stability when exposed to an accelerated weathering, compared to pristine PC substrates. The mixed silica/zirconia hybrid coatings with a low and intermediate zirconia-to-silica ratio also show excellent mechanical strength, high level of hardness and superior integrity after long-term light exposure. [ABSTRACT FROM AUTHOR]

The aim of this work was to develop new bioplastic compounds from wheat gluten, biobased plasticizers (glycerol, octanoic acid and 1,4-butanediol), and microalgal biomass as a filler. The effects of the composition on tensile properties, thermal stability, and water sensitivity were investigated. Microalgal biomass was added with the selected quantities: 10, 20, and 30 per hundred parts (php). Mechanical mixing of the components, i.e., gluten, plasticizer, and microalgae, was followed by molding in a hot press. Microlgal filler improved mechanical properties of the plasticized gluten material: in samples plasticized with 1,4-butanediol, 30 php of biomass increased the tensile modulus by nearly one order of magnitude, from 36.5 MPa to 273.1 MPa, and it also increased the tensile strength from 3.3 MPa to 4.9 MPa. The introduction of microalgal biomass slightly increased the surface sensitivity against water: 30 php of biomass reduced the water contact angle from 41° to 22° in samples plasticized with glycerol, but the biomass lowered the overall water absorption kinetics for material with each plasticizer. Microalgal biomass proved therefore to be an interesting sustainable resource with which to develop materials based on gluten, in particular to increase the mechanical properties of the compounds without reducing thermal stability or water resistance. [ABSTRACT FROM AUTHOR]

This paper deals with the additive manufacturing of metakaolin-based geopolymers and with the use of microalgal biomass from wastewater treatment plants as biofiller in this kind of cementitious material. The study was developed following the evolution stages of the material, which was prepared and printed as a soft paste and then hardened thanks to an inorganic polymerization reaction (geopolymerization). Thus, the characterization techniques adopted encompassed rheometry, mechanical tests performed on the hardened material, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and mercury intrusion porosimetry (MIP). Microalgal biomass addition, evaluated in this study at 1, 3 and 5 php with respect to the powder weight, affected both the properties of the fresh and of the hardened material. Regarding the former aspect, biomass reduced the yield stress of the pastes, improving the ease of the extrusion process, but potentially worsening the ability to build structures in height. When hardened, geopolymers containing microalgae showed mechanical properties comparable to the unfilled material and a microstructure characterized by smaller pores. Finally, a printing test was successfully performed with a larger printer to assess the feasibility of producing large-scale structures. Taking into account these results, this study demonstrates the possibility of using microalgal biomass as biofiller in geopolymers for additive manufacturing. [ABSTRACT FROM AUTHOR]

The amount of compostable bioplastics collected with the food waste is constantly growing, particularly due to the bags used for collection. According to the Italian legislation, compostable bioplastics must be accepted by all biological treatment plants, including aerobic and anaerobic facilities. Anyway, the compostability standard requires only the assessment of the aerobic degradability, while it is generally not required to test the behaviour under anaerobic conditions. This aspect is evaluated in the paper, where the anaerobic degradability of bioplastic bags used for the food waste collection is assessed. First, Biochemical Methane Potential (BMP) tests were performed on four commercial types of bioplastic bags, including those designed only for the collection of food waste and the shoppers, that can be reused for the same purpose. Subsequently, an innovative approach for this kind of substrate was applied, subjecting two bags to semi-continuous co-digestion tests together with the food waste. Both tests were performed by comparing the behaviour of bioplastic bags with that of an alternative collection paper bag. Finally, tests to evaluate the influence of physical phenomena on the degradation of bioplastics were performed to better understand the results of biological tests. BMP tests indicated a good degradability (>71%) of bioplastic bags, while semi-continuous tests showed a much lower degradability (<27%), confirmed by the observation of the undigested bag pieces. On the contrary, the paper bag presents interesting characteristics, because its degradability in the semi-continuous tests (82%) resulted even higher than that observed in the BMP tests (74%). These results highlight an important difference between the bags mono-digestion by means of BMP tests and the semi-continuous co-digestion tests with food waste, which better simulate the full-scale operational conditions. [Display omitted] • Bioplastic and paper bags were tested with BMP and semi-continuous digestion tests. • Paper bags show a good degradability in both the tests (>74%). • The BMP tests on bioplastic bags indicate a good degradability (>71%). • Semi-continuous digestion of bioplastics with food waste shows a low degradability. • The degradability of bioplastics is influenced by physical factors. [ABSTRACT FROM AUTHOR]