Hybrid Graphenene Oxide/Cellulose Nanofillers to Enhance Mechanical and Barrier Properties of Chitosan-Based Composites.

Chitosan-based hybrid nanocomposites, containing cellulose nanocrystals (CNCs), graphene oxide (GO), and borate as crosslinking agents, were successfully prepared by solution-casting technique. The synergistic effect of the two fillers, and the role of the cross-linker, in enhancing the structural and functional properties of the chitosan polymer, was investigated. XPS results confirm the chemical interaction between borate ions and hydroxyl groups of chitosan, GO, and CNCs. The morphological characterization shows that the GO sheets are oriented along the casting surface, whereas the CNC particles are homogenously distributed in the sample. Results of tensile tests reveal that the presence of graphene oxide enhances the elastic modulus, tensile strength, elongation at break, and toughness of chitosan, while cellulose and borate induce an increase in the elastic modulus and stress at the yield point. In particular, the borate-crosslinked chitosan-based sample containing 0.5 wt% of GO and 0.5 wt% of CNCs shows an elongation at a break value of 30.2% and a toughness value of 988 J*m-3 which are improved by 124% and 216%, respectively, compared with the pristine chitosan. Moreover, the water permeability results show that the presence of graphene oxide slightly increases the water barrier properties, whereas the borate and cellulose nanocrystals significantly reduce the water vapor permeability of the polymer by about 50%. Thus, by modulating the content of the two reinforcing fillers, it is possible to obtain chitosan-based nanocomposites with enhanced mechanical and water barrier properties which can be potentially used in various applications such as food and electronic packaging.

MWCNT/rGO/natural rubber latex dispersions for innovative, piezo-resistive and cement-based composite sensors.

The present study is focused on the development and characterization of innovative cementitious-based composite sensors. In particular, multifunctional cement mortars with enhanced piezoresistive properties are realized by exploiting the concept of confinement of Multiwall Carbon Nanotubes (MWCNTs) and reduced Graphene Oxide (rGO) in a three-dimensional percolated network through the use of a natural-rubber latex aqueous dispersion. The manufactured cement-based composites were characterized by means of Inelastic Neutron Scattering to assess the hydration reactions and the interactions between natural rubber and the hydrated-cement phases and by Scanning Electron Microscopy and X-Ray diffraction to evaluate the morphological and mineralogical structure, respectively. Piezo-resistive properties to assess electro-mechanical behavior in strain condition are also measured. The results show that the presence of natural rubber latex allows to obtain a three-dimensional rGO/MWCNTs segregate structure which catalyzes the formation of hydrated phases of the cement and increases the piezo-resistive sensitivity of mortar composites, representing a reliable approach in developing innovative mortar-based piezoresistive strain sensors.

Effect of carbonaceous fillers on adsorption behavior of multifunctional diatomite-based foams for wastewater treatment.

Nowadays the study of the potential applications of multifunctional materials for environmental remediation is one of the main goals of the materials engineering. Multifunctional porous materials, MPMs, incorporate, all in once, different and multiple functionalities that make them suitable for several uses and can satisfy many purposes at the same time. Multifunctional diatomite-based foams with a hierarchical porosity, already produced and characterized to be applied in building as well as aerospace sectors, are proposed as adsorbents for inorganic and organic pollutants removal from wastewaters. Then, the effect of the addition of different carbonaceous nanofillers (graphite, graphene and graphene oxide) on the water purification efficiency of the adsorbent was evaluated. Firstly, pristine MPM showed the best performance in adsorbing Indigo Carmine due to its intrinsic chemism and hierarchical porosity (at macro-, micro- and nano-level), but it is not the best with respect to the Cd2+ adsorption, if compared with the nanocomposites. Among the nanocomposite products, both graphene- and graphene oxide-MPM samples showed a significantly improved adsorption capacity towards Cd2+. This behavior is due to the synergistic effect of the finer morphology, higher available foam surface, and the highly exfoliated fillers, graphene and graphene oxide, which permit a better dispersion into the matrix.

Process strategy to fabricate a hierarchical porosity gradient in diatomite-based foams by 3D printing.

Motivated by the hierarchical micro and nanoscale features in terms of porosity of diatomite, the production of ceramic-graded porous foams with tailored porosity, obtained by using it as raw material, has been proposed. The main challenge during the foam-production process has been the preservation of diatomite nanometric porosity and the addition of other levels of hierarchical porosity. The coupled use of two techniques of direct foaming (chemical and mechanical), combined with the use of 3D printing inverse replica method, assured the achievement of porosity of, respectively, microscopic and macroscopic dimensions. Optical and scanning electron microscopies have been performed for an in-depth characterization of the final microstructure. XRD analysis has been carried out to check the influence of sacrificial templates on the matrix mineralogical composition. The porosity of the diatomite-based foams has been investigated by means of nitrogen-adsorption analysis and mercury-intrusion porosimetry. The experimental tests confirmed the presence of different porous architectures ranging over several orders of magnitudes, giving rise to complex systems, characterized by hierarchical levels of porosity. The presence of porosity of graded dimensions affects the final mechanical performances of the macroporous diatomite-based foams, while their mineralogical composition does not result to be affected by the addition of templates.

Tuning of polyurethane foam mechanical and thermal properties using ball-milled cellulose.

Cystalline-Cc and ultra-milled Amorphous-Ca cellulose were used as reactive filler to tune the performances of composite polyurethane-cellulose-foams, PUC. The effect of Cc and Ca on chemo-physical and mechanical properties of PUC was analysed through FTIR, morphological analysis, thermal conductivity and compression measurements. FTIR results show that, both Cc and Ca react with isocyanate through the OH functional groups contributing to the formation of a tough cellulose-polyurethane network. Morphological observations show that the addition of both Cc and Ca induces a decrease of average cell-size compared to the pristine-PU, thus confirming that they act as nucleating agent. In addition, the better dispersion of the Ca in the polyol, with respect to Cc induces, a finer cell leading to a reduction of the thermal conductivity around 33 % (for the composite loaded with 20 %wt-Ca) with respect to pristine-PU. Finally, the addition of Ca highly reactive modifies the mechanical behaviour from rigid-brittle to semi-rigid.

Optimization of dye adsorption capacity and mechanical strength of chitosan aerogels through crosslinking strategy and graphene oxide addition.

Chitosan (CS) aerogels were prepared by freeze-drying as potential adsorbents for water purification, and the effect of the strategy of crosslinking was investigated by varying the amount of crosslinker (glutaraldehyde) and the sequence of steps for the preparation of the aerogel. Two procedures were compared, in which the crosslinking step was carried out before or after the freeze-drying of the starting CS solution. When crosslinking was postponed after the freeze-drying step, the adsorption capacity towards an anionic dye, such as indigo carmine, considerably increased (up to +45%), reaching values as high as 534.4 ± 30.5 mg g-1. The same crosslinking strategy ensured a comparable improvement also in nanocomposite aerogels containing graphene oxide (GO), which was added to enhance the mechanical strength and provide adsorption capacity towards cationic dyes. Besides possessing good mechanical strength (compressive modulus higher than 1 MPa), the CS/GO aerogels were able to bind also cationic pollutants such as methylene blue. The maximum uptake capacity increased from 4.3 ± 1.6 to 168.6 ± 9.6 mg of cationic dye adsorbed per gram of adsorbent with respect to pristine CS aerogels.

Characterization of sustainable polyhydroxyls, produced from bio-based feedstock, and polyurethane and copolymer urethane-amide foams.

This manuscript presents data related to the research article entitled "Synthesis and characterization of sustainable polyurethane foams based on polyhydroxyls with different terminal groups" (DOI: 10.1016/j.polymer.2018.06.077) [1]. We provide Supplementary data on the chemical properties, in terms of FTIR characterization, of polyhydroxyls produced starting from bio-based feedstock (biosuccinic acid and 1,4 butandiol) and thermal properties (glass transition temperature-Tg and thermal degradation behavior) of polyurethane and copolymer urethane-amide foams manufactured from the aforementioned polyhydroxyls. The FTIR characterization elucidates the chemical structure of polyhydroxyls and allows to make some hypothesis on their reaction routes with the isocyanate molecules. The thermal characterization revealed that the addition of bio-based polyhydroxyls to the sample formulations improves both the glass transition and degradation temperature of the foams. These foamed products exhibit potential performances to be applied as a substitute for conventional polyurethane foams.

Treatment and recycling of asbestos-cement containing waste.

The remediation of industrial buildings covered with asbestos-cement roofs is one of the most important issues in asbestos risk management. The relevant Italian Directives call for the above waste to be treated prior to disposal on landfill. Processes able to eliminate the hazard of these wastes are very attractive because the treated products can be recycled as mineral components in building materials. In this work, asbestos-cement waste is milled by means of a high energy ring mill for up to 4h. The very fine powders obtained at all milling times are characterized to check the mineralogical and morphological transformation of the asbestos phases. Specifically, after 120 min of milling, the disappearance of the chrysotile OH stretching modes at 3690 cm(-1), of the main crystalline chrysotile peaks and of the fibrous phase are detected by means of infrared spectroscopy and X-ray diffraction and scanning electron microscopy analyses, respectively. The hydraulic behavior of the milled powders in presence of lime is also tested at different times. The results of thermal analyses show that the endothermic effects associated to the neo-formed binding phases significantly increase with curing time. Furthermore, the technological efficacy of the recycling process is evaluated by preparing and testing hydraulic lime and milled powder-based mortars. The complete test set gives good results in terms of the hydration kinetics and mechanical properties of the building materials studied. In fact, values of reacted lime around 40% and values of compressive strength in the range of 2.17 and 2.29 MPa, are measured.

Heavy metal stabilization by means of innovative alumino-silicate matrix.

Powdered tuff mixed with NaOH solution has been hydrothermally cured at temperatures ranging from 90 to 150 degrees C. Hardening takes place due to the formation of an amorphous binding phase. At the lowest temperature tested a non-autoclaved process can be carried out. Values of unconfined compressive strength were found to vary from 15.5 MPa to 28.9 MPa depending on reaction conditions. The matrix was tested as a binder for the stabilization of model systems containing cadmium, chromium and lead and for a real system containing a secondary lead smelter slag. The stabilization process was tested from both the environmental and technological points of view by means of leahcing tests and compressive strength measurement. Basic characterization leaching tests carried out with the model systems showed that metal release from hardened paste is below 1%. Compliance leaching test carried out with the real system showed that lead release is below the limit set by law. From the technological pont of view, it was found that unconfined compressive strength is always higher for the real system. Specifically, this system showed compressive strength increasing with slag content to values exceeding 86.5 MPa.