Synthesis of flame retardant polyester‐urethanes and their applications in nanoclay composites and coatings

This paper describes the synthesis of phosphorus‐containing polyester‐urethanes and their applications in nanoclay composites and coatings. Polyester was prepared by the reaction of bis(bisphenol‐A) monophenyl phosphonate, maleic anhydride and phthalic anhydride. The polyester was reacted with various diols such as ethylene glycol, diethylene glycol and propylene glycol to obtain polyester polyols. Synthesized polyester polyols were characterized by chemical analysis and instrumental analysis and was used further to react with different isocyanates to develop polyester‐urethanes. The synthesized polyester‐urethanes were blended with organo‐modified montmorillonite nanoclay (1 wt%, 3 wt% and 5 wt%) and were cast in a mold and coated on mild steel panels. The thermal stability of neat polyester‐urethane and the nanoclay composites was determined by thermogravimetric analysis. The flame retardant properties of cast films and their composites were determined by the limiting oxygen index and UL‐94 test methods. The physical and mechanical properties of coatings such as pot life, drying properties, scratch hardness, pencil hardness, impact resistance, adhesion and flexibility were investigated. The chemical resistance properties of the coatings were also determined in different reagents. The data reveal that the polyester‐urethane nanoclay composites with 3 wt% clay hold promise for use in effective flame retardant coatings. © 2013 Society of Chemical Industry     

Editorial: Biodegradable Materials

This Special Issue “Biodegradable Materials” features research and review papers concerning recent advances on the development, synthesis, testing and characterisation of biomaterials. These biomaterials, derived from natural and renewable sources, offer a potential alternative to existing non-biodegradable materials with application to the food and biomedical industries amongst many others. In this Special Issue, the work is expanded to include the combined use of fillers that can enhance the properties of biomaterials prepared as films. The future application of these biomaterials could have an impact not only at the economic level, but also for the improvement of the environment.     

Novel approach for attapulgite/poly(acrylic acid) (ATP/PAA) nanocomposite microgels as selective adsorbent for Pb(II) Ion

A novel approach was developed for the preparation of the attapulgite/poly(acrylic acid) (ATP/PAA) nanocomposite microgels via the “one-pot” inverse suspension radical polymerization of acrylic acid (AA) with the multi-functionalized attapulgite nanorods (org-ATP) as the sole crosslinker. The parameters of the feeding ratio of the functional attapulgite (org-ATP) nanorods and AA (org-ATP/AA), oil (liquid paraffin)–water ratio, and feeding ratios of dispersing agent (sodium dodecyl benzene sulfonate (SDBS)) and initiator (ammonium persulfate (APS)) were optimized via 4-Variable 3-Level Orthogonal experiments. Under the optimized preparation condition, more than 85% of the monomer AA had been grafted onto the org-ATP nanorods to form the 3-dimensional network of the ATP/PAA nanocomposite microgel. The ATP/PAA nanocomposite microgel exhibited better mechanical stabilities (resistance to pressure and resistance to agitation) and selective adsorption to heavy metal ions, especially to Pb²⁺. The adsorbed Pb²⁺ ion could be completely eluted with HCl solution. The better mechanical stability and regeneration make it potential adsorbent for the heavy metal contaminated water.     

超级电容器用MnO_2基纳米复合材料的进展

介绍二氧化锰(MnO_2)的结构及储能机理,综述近年来MnO_2作为赝电容材料,通过不同材料改性,以提高电化学性能的研究进展。这些材料主要有碳材料、导电聚合物、金属和金属氧化物/硫化物等。展望由MnO_2基纳米复合材料构建的核壳结构的发展趋势。     

Improvement of β-phase crystal formation in a BaTiO_3-modified PVDF membrane

In this paper,low temperature plasma is used to modify the surface of barium titanate(BaTiO_3)nanoparticles in order to enhance the interfacial compatibility between ferroelectric poly(vinylidene fluoride)(PVDF) and BaTiO_3 nanoparticles.The results demonstrate that oxygenic groups are successfully attached to the BaTiO_3 surface,and the quantity of the functional groups increases with the treatment voltage.Furthermore,the effect of modified BaTiO_3 nanoparticles on the morphology and crystal structure of the PVDF/BaTiO_3 membrane is investigated.The results reveal that the dispersion of BaTiO_3 nanoparticles in the PVDF matrix was greatly improved due to the modification of the BaTiO_3 nanoparticles by air plasma.It is worth noting that the formation of a β-phase in a PVDF/modified BaTiO_3 membrane is observably promoted,which results from the strong interaction between PVDF chains and oxygenic groups fixed on the BaTiO_3 surface and the better dispersion of BaTiO_3 nanoparticles in the PVDF matrix.Besides,the PVDF/modified BaTiO_3 membrane at the treatment voltage of 24 k V exhibits a lower water contact angle(≈68.4°) compared with the unmodified one(≈86.7°).Meanwhile,the dielectric constant of PVDF/BaTiO_3 nanocomposites increases with the increase of working voltage.     

Production of biodiesel from castor oil using iron (II) doped zinc oxide nanocatalyst

The depletion of fossil fuels has caused the price of petroleum to rise remarkably and created need for alternative energy such as biodiesel. In the present study, the biodiesel was produced from castor oil using ferromagnetic zinc oxide nanocomposite as heterogeneous catalyst for transesterification reaction. Single phase of nanocatalyst were confirmed by X-Ray Diffraction analysis. The spherical shape of the aggregated nanocatalyst was observed in Scanning Electron Microscopy. Magnetic properties were analysed using vibrating sample magnetometer. Atomic Force Microscopic analysis revealed the larger surface area and roughness of nanocatalyst. The biodiesel yield of 91% (w/w) was obtained in 50 min at 55 °C with 14 wt % catalyst loading and 12:1 methanol/oil ratio and was confirmed by Gas chromatograph with Mass Spectrometer. The result showed that the iron (II) doped ZnO nanocatalyst is a promising catalyst for the production of biodiesel via heterogeneous catalytic transesterification under milder reaction conditions.     

Piezoelectric sensor based on electrospun PVDF-MWCNT-Cloisite 30B hybrid nanocomposites

Piezoelectric materials have attracted substantial interest in applications such as sensors and actuators. Ferroelectric and piezoelectric polymeric fibers doped with nanoparticles are made for use in nanoscale electronic devices. In this paper, we report on poly (vinylidene fluoride) (PVDF) nanocomposites doped with different ratios of multi-walled carbon nanotube (MWCNT) and Cloisite 30B (OMMT) nanoclay prepared by electrospinning technique. The effect of different ratios of OMMT and MWCNT nanofillers and potential synergistic effect of these fillers on the crystalline structure of PVDF and the performance of resulting piezo-device were studied. Results showed that OMMT increases beta phase crystals and piezoelectric properties of PVDF as compared with MWCNT. Meanwhile, MWCNT decreases impedance and increases dielectric constant of PVDF as compared with OMMT. The acoustic absorption behavior of PVDF/MWCNT/OMMT hybrid nanocomposite was also investigated. It was found that the sound absorption efficiency of PVDF/MWCNT/OMMT hybrid nanocomposites was increased compared with that of pure PVDF fibers and film. No synergistic effect of OMMT and MWCNT on the properties of PVDF was observed.     

UV‐cured epoxy/graphene nanocomposite films: preparation,structure and electric heating performance

UV‐cured epoxy/graphene nanocomposite films with ca 100 µm thickness were manufactured by a facile cationic photopolymerization of 3,4‐epoxycyclohexylmethyl‐3′,4′‐epoxycyclohexane carboxylate mixtures including graphene sheets of 0.3 ? 10.0 wt%, which was initiated by triarylsulfonium hexafluoroantimonate salts. The microstructure and thermal and electrical properties of the UV‐cured epoxy/graphene nanocomposite films were investigated as a function of the graphene content. X‐ray diffraction patterns and TEM images confirm that graphene sheets are well dispersed in the UV‐cured epoxy resin matrix even with a high graphene content of 10.0 wt%. The electrical resistance of the nanocomposite films decreased dramatically from ca 10¹² Ω to ca 10² Ω with increasing graphene content, especially at a percolation threshold of 2.0 ? 3.0 wt%. Accordingly, the UV‐cured nanocomposite films including 5.0 ? 10.0 wt% graphene showed excellent electric heating performance in terms of temperature response as well as electric power efficiency at a given applied voltage. For a nanocomposite film with 10.0 wt% graphene, the maximum temperature of ca 138 °C was attained at an applied voltage of 15 V and a high electric power efficiency of ca 3.0 ± 0.3 mW °C^?1 was achieved. © 2014 Society of Chemical Industry     

Highly-reproducible nonvolatile memristive devices based on polyvinylpyrrolidone: Graphene quantum-dot nanocomposites

The properties of nonvolatile memristive devices (NMD) fabricated utilizing organic/inorganic hybrid nanocomposites were investigated due to their superior advantages such as mechanical flexibility, low cost, low-power consumption, simple technological process in fabrication and high reproducibility. The current-voltage (I-V) curves for the Al/polyvinylpyrrolidone (PVP): graphene quantum-dot (GQD)/indium-tin-oxide (ITO) memristive devices showed current bistability characteristics at 300 K. The window margins corresponding to the high-conductivity (ON) state and the low-conductivity (OFF) state of the devices increased with increasing concentration of the GQDs. The ON/OFF ratio of the optimized device was 1 × 10⁴, which was the largest memory margin among the devices fabricated in this research. The endurance number of ON/OFF switching was above 1 × 10² cycles, and the retention time was relatively constant, maintaining a value above 10⁴ s. The devices showed high reproducibility with the writing voltage being distributed between −0.5 and −1.5 V and the erasing voltage being distributed between 2 and 3 V. The ON state currents remained between 0.02 and 0.03 A, and the OFF state currents stayed between 10⁻⁶ and 10⁻⁴ A. The carrier transport mechanisms are illustrated by using both the results obtained by fitting the I-V curves and the energy band diagrams of the devices.