Morphology, thermal, mechanical properties and ageing of nylon 6,6/graphene nanofibers as Nano2 materials

Nylon 6,6 nanofibers loaded with different Graphene (G) amounts were successfully produced with stable process and good fiber quality, using an optimized solvent system suitable both for electrospinning and for G-suspension. G addition is found to significantly affect diameter but not thermal behaviour. A new phenomenological model is proposed for the interpretation of mechanical behaviour of nanofibrous mat, trying to take into account the nanofibrous morphology. The model highlights a G contribution to mechanical properties that mainly affects the initial steps of deformation where fibers stretch, slide, twist and re-orient. Finally, the nanofibers were analysed after 20 months ageing, showing no significant alteration with respect to the pristine ones, thus the lack of detrimental ageing-effects due to G addition

Production of Thermoplastic Composite Filaments for Additive Manufacturing using Recycled Carbon Fibers

The present work reports the use of recycled carbon fibers (rCF), obtained from pyro-gasification treatment of carbon fibers reinforced polymers (CFRP), to produce a thermoplastic composite filament for additive manufacturing, in particular fused deposition modeling (FDM) process. Polylactic acid (PLA), a thermoplastic biobased and biodegradable polymer, is used as matrix for the composite filament, as it is the most common plastic used in FDM due to its good mechanical properties, stiffness, and strength. Upon production process optimization, filaments with rCF loadings of 5 and 10% wt are produced and analyzed. A particular attention is devoted to the evaluation of the production process on the carbon fibers (CFs) length and the study of the thermal and mechanical properties of the obtained composite materials

Side-Chain Multifunctional Photoresponsive Polymeric Materials

The contribute reviews the recent literature concerning the state-of-the-art of the research on amorphous polymeric derivatives bearing side-chain photoactive moieties such as the azo-aromatic and the carbazole chromophore as functional groups, in addition to the presence of structural or chemical features suitable to also provide the macromolecules of chiral properties

Water-Resistant Photo-Crosslinked PEO/PEGDA Electrospun Nanofibers for Application in Catalysis

Catalysts are used for producing the vast majority of chemical products. Usually, catalytic membranes are inorganic. However, when dealing with reactions conducted at low temperatures, such as in the production of fine chemicals, polymeric catalytic membranes are preferred due to a more competitive cost and easier tunability compared to inorganic ones. In the present work, nanofibrous mats made of poly(ethylene oxide), PEO, and poly(ethylene glycol) diacrylate, PEGDA, blends with the Au/Pd catalyst are proposed as catalytic membranes for water phase and low-temperature reactions. While PEO is a water-soluble polymer, its blending with PEGDA can be exploited to make the overall PEO/PEGDA blend nanofibers water-resistant upon photo-crosslinking. Thus, after the optimization of the blend solution (PEO molecular weight, PEO/PEGDA ratio, photoinitiator amount), electrospinning process, and UV irradiation time, the resulting nanofibrous mat is able to maintain the nanostructure in water. The addition of the Au-6/Pd-1 catalyst (supported on TiO2) in the PEO/PEGDA blend allows the production of a catalytic nanofibrous membrane. The reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP), taken as a water phase model reaction, demonstrates the potential usage of PEO-based membranes in catalysis

Rubbery nanofibrous interleaves enhance fracture toughness and damping of CFRP laminates

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How Nanofibers Carry the Load: Toward a Universal and Reliable Approach for Tensile Testing of Polymeric Nanofibrous Membranes

Nanofibrous nonwovens show high versatility and outstanding properties, with reduced weight. Porous morphology, high material flexibility and deformability challenge their mechanical testing, severely affecting results reliability. Still today, a specific technical standard method to carry out tensile testing of nonwoven nanofibrous mats is lacking, as well as studies concerning tensile test data reliability. In this work, an accurate, systematic, and critical study is presented concerning tensile testing of nonwovens, using electrospun Nylon 66 random nanofibrous mats as a case study. Nanofibers diameter and specimen geometry are investigated to thoroughly describe the nanomat tensile behavior, also considering the polymer thermal properties, and the nanofibers crossings number as a function of the nanofibers diameter. Below a threshold value, which lies between 150 and 250 nm, the overall mat mechanical behavior changes from ductile to brittle, showing enhanced elastic modulus for a high number of nanofibers crossings. While specimen geometry does not affect tensile results. Stress–strain data are analyzed using a phenomenological data fitting model to better interpret the tensile behavior. The experimental results demonstrate the high reliability of the proposed mass-based load normalization, providing a simple, effective, and universally suitable method for obtaining high reproducible tensile stress–strain curves

How Nanofibers Carry the Load: Toward a Universal and Reliable Approach for Tensile Testing of Polymeric Nanofibrous Membranes

Nanofibrous nonwovens show high versatility and outstanding properties, with reduced weight. Porous morphology, high material flexibility and deformability challenge their mechanical testing, severely affecting results reliability. Still today, a specific technical standard method to carry out tensile testing of nonwoven nanofibrous mats is lacking, as well as studies concerning tensile test data reliability. In this work, an accurate, systematic, and critical study is presented concerning tensile testing of nonwovens, using electrospun Nylon 66 random nanofibrous mats as a case study. Nanofibers diameter and specimen geometry are investigated to thoroughly describe the nanomat tensile behavior, also considering the polymer thermal properties, and the nanofibers crossings number as a function of the nanofibers diameter. Below a threshold value, which lies between 150 and 250 nm, the overall mat mechanical behavior changes from ductile to brittle, showing enhanced elastic modulus for a high number of nanofibers crossings. While specimen geometry does not affect tensile results. Stress\u2013strain data are analyzed using a phenomenological data fitting model to better interpret the tensile behavior. The experimental results demonstrate the high reliability of the proposed mass-based load normalization, providing a simple, effective, and universally suitable method for obtaining high reproducible tensile stress\u2013strain curves

Managing heat phenomena in epoxy composites production via graphenic derivatives: synthesis, properties and industrial production simulation of graphene and graphene oxide containing composites

A commercial two-components epoxy resin formulation was successfully modified by adding graphene and related materials (GRMs) and the effect of these nanofillers was assessed on their thermomechanical properties as well as on the simulation of their industrial application for the production of thick composites objects with interesting results. GMRs were added in different concentrations in order to improve thermo-mechanical properties of the nano-composite thermoset. Different dispersion methods were taken into account in order to produce stable long-lasting dispersion of the GRMs, that can withstand a commercial shelf life. Addition of the GRMs improves the glass transition temperature of the nanocomposite up to 20 °C with respect to the plain commercial formulation, and both stress and elongation at break increase up to almost 4 times the original values. Moreover, the industrial curing of some of the more promising modified resins was computer-simulated when the two-components resins are used to produce a carbon-fibre reinforced thick composite beam. Simulation results show that some of the applied GRMs helps reducing or even completely preventing the overheat phenomena that are well renown to induce significant thermal stresses negatively affecting the final object performances. These interesting effects would contribute reducing the time required for a single industrial production cycle, since no time for overheat dispersion is required, thus helping increasing the production rate

Synthesis of functionalized iron N-heterocyclic carbene complexes and their potential application as flame behavior modifier in cross linked epoxy resins

The design of new flame retardants (FR) that avoid the use of halogen and phosphorus additives is challenging and urgent. Herein we report on the synthesis of bis-amino functionalized N-heterocyclic carbene cyclopentadienone iron complexes aimed at promoting the production of iron containing epoxy resins. Iron complexes are successfully employed to obtain high Tg thermosets with as low as 5% hardener content. Moreover the obtained resins display an impressive charring ability that paves the way to the application of such systems for material with improved flame behavior

Erratum to 'Core Biopsies from Prostate Cancer Patients in Active Surveillance Protocols Harbor PTEN and MYC Alterations'[European Urology Oncology 2 (2019) 277-285].

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