Layer-by-layer assembly of silica-based flame retardant thin film on PET fabric

A novel method to improve flame retardant properties of textile fabric using multilayered thin films was evaluated. In this work, PET fabrics were coated with silica nanoparticles using layer-by-layer assembly. Five bilayers of positively and negatively charged colloidal silica (<10 nm average thickness) increased time to ignition and decreased heat release rate peak of PET fabric by 45% and 20%, respectively. In vertical burn test, this same nanocoating dramatically reduced burn time and eliminated melt dripping. This study demonstrates the ability to impart flame retardant behavior using a water-based, environmentally-friendly protective coating.     

Hydrotalcite and nanometric silica as finishing additives to enhance the thermal stability and flame retardancy of cotton

Suspensions of nanoparticles (namely, hydrotalcite and nanometric silica) have been employed during the finishing of cotton in order to improve its thermal stability and/or flame retardancy. The immersion approach has also been coupled to a surface pre-treatment of the textile by cold oxygen plasma in order to load a higher amount of nanoparticles onto fibres. The time of immersion and the resulting distribution of the nanoparticles onto the fibres, evaluated by scanning electron microscopy in combination with elemental analysis, have been thoroughly investigated. The present study has shown that the above parameters are functions of nanoparticle type. Pre-treatment by cold plasma has been found to be more effective than the immersion only. As far as the thermal stability and the combustion behaviour of treated cotton are concerned, the nanoparticles turned out to be able to delay the degradation in air, modifying mechanism and kinetics, and at the same time enhancing the flame retardancy of cotton by increasing the time to ignition and decreasing the heat release rate peak during the combustion. The joint effect of the two nanoparticles has also been evaluated and found more efficient than the effect of single species.     

Synthesis of bromoallenyl pyrrolidines via 1,4-addition to 1,3-enynes

The discovery of the novel reactivity of conjugated enynes,mediated by readily available halogenation reagents,opens a broad range of mechanistically unique pathways for the synthesis of highly functionalized chiral allene derivatives.Bromoallenyl pyrrolidines can be synthesized via 1,4-addition of sulfonamide nitrogen nucleophiles and halogens to conjugated enynes.This process can lead to simultaneous formation of a highly functionalized axially chiral allene and a stereogenic center under economical and e...     

Dispersive and non-dispersive hole transport in fluorene-arylamine copolymers

Hole transport in two fluorene-arylenediamine copolymers is studied by means of time-of-flight (ToF) and space-charge-limited dark-injection (SCL DI) transient current methods. Non-dispersive and dispersive hole transport is observed for a range of sample thicknesses, applied electric fields and temperatures.     

Structural-transformation-induced Drastic Luminescence Changes in an Organic-Inorganic Hybrid [ReN(CN)4]2− Salt Triggered by Chemical Stimuli

We synthesized a (1-propylpyridinium)₂[ReN(CN)₄]-type organic–inorganic hybrid exhibiting water-vapor-induced drastic structural changes of the [ReN(CN)₄]²⁻ assemblies. Specifically, upon exposure to water vapor, dehydrated nitrido-bridged chains were converted to hydrated cyanido-bridged tetranuclear clusters via rearrangements of large molecular building units in the crystals. These switchable assembly forms display substantially different photo-physical properties, although in both cases the emission is caused by a metal-centered d–d transition. The nitrido-bridged chain exhibited a near-infrared (749 nm) emission, which blue-shifted as the temperature increased, while a visible (561 nm) emission and its red shift was demonstrated by the cyanido-bridged cluster.     

The use of thermographic technique in the evaluation of polymers combustion and fire retardants performance

The combustion behaviour of polymeric materials either fire retarded or not, burning in the Glow Wire and UL 94 tests, was characterised by means of thermography. It is shown that the distribution of temperatures in the gas and condensed phase of the burning specimen thus recorded, supplies fundamental complementary information for the characterisation of the combustion process.     

The use of fluorinated additives in fire retardance of polymers

Polytetrafluoroethylene (PTFE) is shown to improve fire retardance characteristics of brominated compounds/antimony trioxide systems added to polymers burning with or without dripping, as for example high-impact polystyrene or acrylonitrilebutadiene-styrene terpolymer, respectively. The action of PTFE seems to be the reduction of intrinsic flammability of the material as shown by parallel improvement of Underwriters Laboratories (UL94) tests and oxygen index parameters. A mechanistic interpretation is tentatively proposed which takes into account the very high effectiveness of PTFE.