Multifunctional leather finishing vs. applications, through the addition of well-dispersed flower-like nanoparticles

In the present paper, multifunctional flower-like nanoparticles were synthesized to be used in the leather finishing. They are capable of conferring simultaneously and synergistic antimicrobial, self-cleaning, light resistance, hydrophobic, mechanical, thermal, and fluorescent properties due to the presence of Ag, TiO2, and SiO2 NPs. These nanoparticles form a "flower-like" structure in which the "pistil" is made up of TiO2 and the "petals" that surround it of silver nanoparticles and silica nanoparticles, whose dimensions are of the order of ten nanometers. Their surfaces enjoy abundant hydrophilic functionalities to be dispersed within inks commonly used during the leather finishing process. Leathers functionalized with these nanomaterials showed significantly improved self-cleaning properties after 15 h of exposure to UV light, and antibacterial properties 10 times higher than that shown by the untreated samples. Aging tests were performed (ISO 105-B02, ISO 17228, SAEJ 2412). ΔE, color variation decreased by approximately 30%, if compared with samples not refined with flower-like NPs. Furthermore, the results of the mechanical tests (ISO 17076, FCA 50444) evidence amazing properties, e.g. abrasion resistance more than significantly improved, increase in resistance from 1500 cycles for the untreated samples to 3000 cycles for the leathers finished with flower-like NPs. The contact angle analysis, capturing the angle that traces the air-water to water-substrate interface from the origin of the air-water-substrate contact point at the edge, is practically unchanged after 10 s in the case of nanoparticles containing finishing.

Advanced Nanomechanical Characterization of Biopolymer Films Containing GNPs and MWCNTs in Hybrid Composite Structure

Nanomechanical definition of the properties of composite specimens based on polylactic acid (PLA) was made in the present study. Research activities with accent on biodegradable polymer nanocomposites have fundamental significance originated from the worldwide plastic waste pollution. To receive hybrid nanocomposites with high level of homogeneity, the low cost and environmentally friendly melt extrusion method has been applied. The role of graphene nanoplatelets (GNPs) and multiwall carbon nanotubes (MWCNTs) as reinforcing nanoparticles dispersed in the polymer matrix was thoroughly investigated. Quasi-static nanoindentation analysis was enriched by performance of accelerated property mapping and nanodynamic mechanical testing in order to fully describe the nanoscale surface homogeneity and stress relaxation behavior of the nanocomposite specimens. That novelty of the research approach had a well-marked contribution over the detection of the new samples’ nanomechanical features as a function of the type of carbon nanofiller. Refined nanoscratch experiments uncovered the resistance of the materials against notches by means of measurement of the coefficient of friction and accurate estimation of the residual penetration depth.

Essential Nanostructure Parameters to Govern Reinforcement and Functionality of Poly(lactic) Acid Nanocomposites with Graphene and Carbon Nanotubes for 3D Printing Application

Poly(lactic) acid nanocomposites filled with graphene nanoplatelets (GNPs) and multiwall carbon nanotubes (MWCNTs) are studied, varying the filler size, shape, and content within 1.5-12 wt.%. The effects of the intrinsic characteristics of nanofillers and structural organization of nanocomposites on mechanical, electrical, thermal, and electromagnetic properties enhancement are investigated. Three essential rheological parameters are identified, which determine rheology-structure-property relations in nanocomposites: the degree of dispersion, percolation threshold, and interfacial interactions. Above the percolation threshold, depending on the degree of dispersion, three structural organizations are observed in nanocomposites: homogeneous network (MWCNTs), segregated network (MWCNTs), and aggregated structure (GNPs). The rheological and structural parameters depend strongly on the type, size, shape, specific surface area, and functionalization of the fillers. Consequently, the homogeneous and segregated network structures resulted in a significant enhancement of tensile mechanical properties and a very low electrical percolation threshold, in contrast to the aggregated structure. The high filler density in the polymer and the low number of graphite walls in MWCNTs are found to be determinant for the remarkable shielding efficiency (close to 100%) of nanocomposites. Moreover, the 2D shaped GNPs predominantly enhance the thermal conductivity compared to the 1D shaped MWCNTs. The proposed essential structural parameters may be successfully used for the design of polymer nanocomposites with enhanced multifunctional properties for 3D printing applications.

Ozone decomposition on Ag/SiO2 and Ag/clinoptilolite catalysts at ambient temperature

Silver modified zeolite (Bulgarian natural clinoptilolite) and Ag/silica catalysts were synthesized by ion exchange and incipient wet impregnation method respectively and characterized by different techniques. DC arc-AES was used for Ag detection. XRD spectra show that Ag is loaded over the surface of the SiO(2) sample and that after the ion-exchange process the HEU type structure of clinoptilolite is retained. UV-VIS (specific reflection at 310 nm) and IR (band at 695 cm(-1)) spectroscopy analysis proved that silver is loaded as a T-atom into zeolite channels as Ag(+), instead of Na(+), Ca(2+), or K(+) ions, existing in the natural clinoptilolite form. The samples Ag/SiO(2) and Ag-clinoptilolite were tested as catalysts for decomposition of gas phase ozone. Very high catalytic activity (up to 99%) was observed and at the same time the catalysts remained active over time at room temperature.