Influence of natural additives on the properties of a milk-based compostable bioplastic.

The ongoing revolution in the plastic sector is the use of renewable and compostable materials obtained from biomass. However, their mechanical strength and thermal stability are generally not sufficient for practical applications. This study investigates the influence of natural additives on the physical-mechanical properties of a new biobased compostable bioplastic, SP-Milk®, produced from milk scraps. To provide this matrix the appropriate mechanical and thermal properties for daily use while leaving its compostability unchanged, the effect of incorporating vegetal fibres and organic particulates into the bulk bioplastic was investigated. Mechanical tests showed that fibres with a length of 2 mm are capable of increasing ductility by up to 97% compared with the original matrix, whereas fibres with a length of 10 mm led to a more effective reinforcement due to the residual resistance effect, increasing the final compressive strain from 20% (original matrix) to 70.9%. The addition of particulate yielded a harder and more resistant material, and the elastic modulus increased by 21%, although with loss of ductility, compared to SP-Milk® alone. The combination of fibres and particles resulted in the preservation of the positive effects of both components, showing a higher elastic modulus (240 ± 20 MPa, compared to 199 ± 12 MPa for the matrix), higher ductility (+50%) and higher strain at failure (+30%), compared with the matrix. Excellent compatibility between the polymeric matrix and both the fibres and the granules was confirmed using scanning electron microscopy. The thermal analysis demonstrated improved thermal stability particularly because of the effect of the combination of granules and fibres. The results validate that natural reinforcement agents are effective and ecologically advantageous.

Characterization of Conductive Carbon Nanotubes/Polymer Composites for Stretchable Sensors and Transducers.

The increasing interest in stretchable conductive composite materials, that can be versatile and suitable for wide-ranging application, has sparked a growing demand for studies of scalable fabrication techniques and specifically tailored geometries. Thanks to the combination of the conductivity and robustness of carbon nanotube (CNT) materials with the viscoelastic properties of polymer films, in particular their stretchability, "surface composites" made of a CNT on polymeric films are a promising way to obtain a low-cost, conductive, elastic, moldable, and patternable material. The use of polymers selected for specific applications, however, requires targeted studies to deeply understand the interface interactions between a CNT and the surface of such polymer films, and in particular the stability and durability of a CNT grafting onto the polymer itself. Here, we present an investigation of the interface properties for a selected group of polymer film substrates with different viscoelastic properties by means of a series of different and complementary experimental techniques. Specifically, we studied the interaction of a single-wall carbon nanotube (SWCNT) deposited on two couples of different polymeric substrates, each one chosen as representative of thermoplastic polymers (i.e., low-density polyethylene (LDPE) and polypropylene (PP)) and thermosetting elastomers (i.e., polyisoprene (PI) and polydimethylsiloxane (PDMS)), respectively. Our results demonstrate that the characteristics of the interface significantly differ for the two classes of polymers with a deeper penetration (up to about 100 µm) into the polymer bulk for the thermosetting substrates. Consequently, the resistance per unit length varies in different ranges, from 1-10 kΩ/cm for typical thermoplastic composite devices (30 µm thick and 2 mm wide) to 0.5-3 MΩ/cm for typical thermosetting elastomer devices (150 µm thick and 2 mm wide). For these reasons, the composites show the different mechanical and electrical responses, therefore suggesting different areas of application of the devices based on such materials.

Tailoring the structural and microstructural properties of nanosized tantalum oxide for high temperature electrochemical gas sensors.

Ta2O5 nanopowders to be used as sensing electrodes in high temperature electrochemical gas sensors for hydrocarbons detection were synthesized using a sol-gel method and their structural and microstructural properties were investigated. The as-synthesized powders were heated at different temperatures in the range 250-1000 degrees C and characterized by TG-DTA, XRD, SEM, TEM and FT-IR. This investigation allowed to identify the correct thermal treatments to achieve the microstructural, textural and functional stability of materials working at high temperature, preserving their nano-metric grain size. Planar sensors fabricated by using Ta2O5 powders treated at 750 degrees C showed promising results for the selective detection of propylene at high temperature (700 degrees C). The good stability of the sensing response after gas exposure at high temperature was correlated to the stable microstructure the electrodes. Thus, Ta2O5 powders seems good candidate as sensing electrode for sensors for automotive exhausts monitoring.

A simple and versatile Sol-Gel method for the synthesis of functional nanocrystalline oxides.

MxOy nanometric powders (Nb2O5, In2O3, and ZrO2) have been efficiently synthesized at low temperatures with the use of simple precursors and with no acid or base catalysis or stabilizing agents. The powders have been characterized by Thermogravimetry/Differential Thermal Analysis, X-ray diffraction, and scanning electron microscopy. The oxides obtained have well-defined crystalline structures, exhibit homogeneity, and crystallite sizes ranging from 9 to 16 nm in diameter.