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<P>The compatibility of thermally reduced graphene (TRG) with multiblock copolyesters, composed of poly(butylene terephthalate) (PBT) segments and poly(tetramethylene ether) glycol segments, was examined in detail. The morphology observed by optical microscopy and scanning electron microscopy showed that the compatibility was enhanced with increasing content of the PBT segment in the polyester. This compatibility behavior was analyzed quantitatively, by using the percolation threshold of electrical conductivity, and then further analyzed by using the Hansen solubility parameters to provide a general quantitative guideline to predict the compatibility of TRG with various polymers. The results suggest that the total solubility parameter, (T), value of TRG is larger than 24.0 (MPa)(1/2), and thus that the compatibility with polymer is enhanced as the (T) value of a polymer increases toward 24.0 (MPa)(1/2). However, this prediction does not fit well in the presence of a comonomer such as acrylic acid, which has a high tendency to hydrogen bond with itself.</P>
<P>Pervaporation is an important alternative membrane separation process compared to the distillation technique, and a relatively high separation factor is required to lower the energy demand. Solution processable nanocomposite membranes prepared by incorporating functionalized graphene sheets (FGS) loaded in various concentrations into the chitosan matrix have been employed for the pervaporative dehydration of ethanol and isopropanol. Incorporation of FGS leads to an increase of surface hydrophilicity of the chitosan membranes along with an increase in membrane tortuosity that was favorable to the selective permeation of water molecules. The nanocomposite membrane containing 2.5 wt % FGS gave the highest selectivities of 7781 and 1093 for isopropanol–water and ethanol–water mixtures, respectively, when tested for 10 wt % water-containing feed mixture. Membranes were characterized by wide-angle XRD, SEM, contact angle, and optical profilometry techniques. The Flory–Huggins theory was employed to estimate the polymer–solvent interaction parameter. Diffusion values and Arrhenius activation energy parameters provided quantitative evidence for the observed increase in water selectivity at higher loading of FGS.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/iecred/2014/iecred.2014.53.issue-37/ie502751h/production/images/medium/ie-2014-02751h_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ie502751h'>ACS Electronic Supporting Info</A></P>
Graphite oxides (GOs) at various oxidation states were examined as fire retardants of epoxy resin. Excessive oxidation is detrimental to the fire retardant effect of GO because it generated a weak GO with reduced intumescent ability. GO manifested optimum fire retardant properties when it was properly oxidized due to the effective intumescence, demonstrating that intumescent GO needs to be strong enough to effectively push the epoxy resin matrix apart to cause efficient intumescence and generate a solid remnant char that acts as an efficient barrier. The fire retardant effect of GO was also reduced when a dispersion of GO in the epoxy resin was enhanced by sonication. This shows that the fine dispersion and disordering of layered structure of GO by the intercalation of epoxy molecules into the gallery of GO also reduced the intumescent ability, and the fire retardant effects of GO.
<P>BACKGROUND: Functionalized graphene sheet (FGS) was recently introduced as a new nano-sized conductive filler, but little work has yet examined the possibility of using FGS as a nanofiller in the preparation of polymer nanocomposites. In particular, there are currently no published papers that evaluate polyurethane/FGS nanocomposites. The purpose of this study was to prepare a polyurethane/FGS nanocomposite and examine the morphological and physical properties of the material.</P><P>RESULTS: A cast nanocomposite film was prepared from a mixture of thermoplastic polyurethane (TPU) solution and FGS suspended in methyl ethyl ketone. The FGS dispersed on the nanoscale throughout the TPU matrix and effectively enhanced the conductivity. A nanocomposite containing 2 parts of FGS per 100 parts of TPU had an electrical conductivity of 10<SUP>−4</SUP> S cm<SUP>−1</SUP>, a 10<SUP>7</SUP> times increase over that of pristine TPU. The dynamic mechanical properties showed that the FGS efficiently reinforced the TPU matrix, particularly in the temperature region above the soft segment melt.</P><P>CONCLUSION: Our results show that FGS has a high affinity for TPU, and it could therefore be used effectively in the preparation of TPU/FGS nanocomposites without any further chemical surface treatment. This indicates that FGS is an effective and convenient new material that could be used for the modification of polyurethane. It could also be used in place of other nano-sized conductive fillers, such as carbon nanotubes. Copyright © 2009 Society of Chemical Industry</P>
Choi, Sang Hyop,Kim, Dong Hoon,Raghu, Anjanapura V.,Reddy, Kakarla Raghava,Lee, Hyung-Il,Yoon, Koo Sik,Jeong, Han Mo,Kim, Byung Kyu Informa UK (TaylorFrancis) 2012 Journal of macromolecular science. Part B Vol.51 No.1
<P><B>Abstract</B></P> <P>Graphene was oxidized with H<SUB>2</SUB>O<SUB>2</SUB> to introduce additional anchoring sites for effective alumina coating on graphene by the sol–gel method. The X-ray photoelectron spectroscopy studies showed that the oxygen-containing groups such as hydroxyl group useful for coating were introduced by the oxidation. The transmission electron microscopy images and thermogravimetric analysis data demonstrated that the additional anchoring sites enhanced the efficiency of the alumina coating. A small amount of alumina-coated graphene synergistically improved the thermal conductivity of the alumina sphere/thermoplastic polyurethane (TPU) composite without any increase in the electrical conductivity, because the electrical conductivity of graphene effectively decreased by the alumina coating. Moreover, the synergistic effect of a small amount of graphene was enhanced by the alumina coating, and the stiffening of the alumina sphere/TPU composite due to the added graphene was alleviated by the alumina coating.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Oxidation of graphene with H<SUB>2</SUB>O<SUB>2</SUB> introduced anchoring sites for alumina coating. </LI> <LI> The anchoring sites improved the efficiency of alumina coating on graphene. </LI> <LI> The alumina-coated graphene synergistically enhanced the thermal conductivity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>