Functionalised graphene sheets as effective high dielectric constant fillers

A new functionalised graphene sheet (FGS) filled poly(dimethyl)siloxane insulator nanocomposite has been developed with high dielectric constant, making it well suited for applications in flexible electronics. The dielectric permittivity increased tenfold at 10 Hz and 2 wt.% FGS, while preserving low dielectric losses and good mechanical properties. The presence of functional groups on the graphene sheet surface improved the compatibility nanofiller/polymer at the interface, reducing the polarisation process. This study demonstrates that functionalised graphene sheets are ideal nanofillers for the development of new polymer composites with high dielectric constant values.PACS: 78.20.Ci, 72.80.Tm, 62.23.Kn     

Structural modification of expandable polystyrene. II. Copolymerization with silicone acrylate

Conventional expandable polystyrene (EPS) was modified by the preparation of copolymers containing 0.10%, 0.25%, and 0.50% silicone acrylate. Copolymeric expandable polystyrene (CEPS) samples were characterized with various techniques. ¹H‐NMR spectroscopy was used for the determination of composition, and gel permeation chromatography was used for the determination of molecular weight and molecular weight distribution. Differential scanning calorimetry showed that the glass‐transition temperatures of the CEPS samples increased with an increasing silicone acrylate content. The surface properties of the copolymers were investigated by contact angle measurement and SEM imaging. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 128–132, 2006     

Viscosity of polydimethylsiloxane gum: Shear and temperature dependence from dynamic and capillary rheometry

The rheology of Dow Corning polydimethylsiloxane gum (PDMS/silicone gum) was studied over a time range of 10^?2 to 10⁵ s^?1 and a temperature range of 23–150°C using both capillary and dynamic rheometry. A low shear Newtonian region is observed at room temperature below 0.01 rad/s (increasing to 0.1 rad/s at 150°C) for which an Arrhenius activation energy for a viscous flow of 13.3 kJ/mol was determined. The Cox–Merz rule for merging of shear and complex viscosities is found to be valid up to 10 s^?1. Viscosity is found to be independent of temperature above 100 s^?1, where terminal power‐law flow is encountered. This is exhibited in the dynamic data as equal plateau moduli for the various temperature curves. Gross wall slippage is seen in capillary flows above approximately 100 s^?1, corresponding to a stress value of 70–100 kPa. Slip‐stick (spurt) flow is not observed. The viscosity data are best fitted by the Carreau–Yasuda model with a fitting parameter a of 0.7, a power‐law index n of 0.05 (low because of slip effect), and a zero shear viscosity of 32 kPa s at 23°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2533–2540, 2002     

Polymerizations of hexamethylcyclosiloxane catalyzed by metal sulfonate/acid chloride combinations

Hexamethylcyclotrisiloxane (D₃) was polymerized in bulk at 100°C, and the conversion was monitored by ¹H‐NMR spectroscopy. Various metal triflates, which were inactive as neat salts, were combined with chlorosilanes, chlorostannanes, phenyl phosphonyl chloride, and carboxylic acid chlorides, which were also inactive when added alone. Most 1 : 1 combinations proved to produce active catalysts for the ring‐opening polymerization of D₃. When the anions of sodium salts were varied alkylsulfonates and the sulfates were more reactive than the triflate. The samarium triflate/diphenyldichlorosilane combination was found to be the most reactive catalyst on the basis of the triflate ions. Regardless of the catalyst combination, the main reaction products in the early stages of all polymerizations were octamethylcyclotetrasiloxane (D₄) and decamethylcyclopentasiloxane (D₅). The polymerization mechanism is discussed. The reactive catalyst combinations also polymerized D₄ at 100°C. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Coating of macroemulsion and microemulsion silicones on poly(ethylene terephthalate) fibers: Evaluation of the thermal properties and flammability

Silicone softeners are widely used in the textile industry to improve the soft handling and aesthetic feel of textiles. These compounds can influence the thermal characteristics and flammability of polyester fabrics, which need to be addressed as important issues of human safety. To do this, the thermal degradation and flammability of macroemulsion and microemulsion silicone coated polyester fibers were studied with various analytical techniques, namely, differential scanning calorimetry, thermogravimetric analysis, dynamical mechanical thermal analysis, and limited oxygen index testing. It has been stated that the electrostatic and hydrophobic interactions of silicone emulsions with polyester can affect their thermal stability. On the other hand, the silicone emulsions present on the surface of poly(ethylene terephthalate) provide a three-dimensional scaffold, which produces faster combustion than pyrolysis. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Flame‐retardant epoxy resin from a caged bicyclic phosphate quadridentate silicon complex

The synergistic effects of phosphorus–silicon in a caged bicyclic phosphate quadridentate silicon complex (CPQS) on the flame retardancy of epoxy resin (EP) were studied with the limiting oxygen index, the UL‐94 test, thermogravimetric analysis, real time Fourier transform infrared spectroscopy, X‐ray powder diffraction, and scanning electron microscopy. The limiting oxygen index data, UL‐94 test, and thermogravimetric analysis results showed that the use of phosphorus and silicon together had a synergistic effect on the flame retardancy of EP. The Fourier transform infrared results and X‐ray powder diffraction measurements provided evidence that CPQS could promote the formation of char with silicophosphate and phosphocarbonaceous structures. The morphological structures observed by scanning electron microscopy demonstrated that more compact charred layers were formed in samples with CPQS than in those with 1‐oxo‐1‐phospha‐2,6,7‐trioxabicyclo[2.2.2]‐4‐hydroxymethyl octane and tetraethoxysilane. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical,surface, and thermal properties of polyamideimide–polydimethylsiloxane nanocomposites fabricated by sol–gel process

Polyamideimide (PAI)–epoxysilane (coupling agent) composites were reacted with oligomeric polydimethylsiloxane (PDMS), a condensation product of difunctional silane, by using the sol–gel process, and were then dried into films. After this procedure, the surface, mechanical, and thermal properties were measured. The study showed that PDMS existed in the PAI matrix by the use of FTIR. With respect to mechanical properties, the maximum elongation and toughness were increased in the PAI with silane groups, although the maximum tensile strength was slightly decreased. In this experiment, PAI–30 wt % epoxysilane composite had the best mechanical properties. The intensive dispersion of the silane groups on the surface of PAI was confirmed through XPS measurement. As a function of the siloxane contents, the TGA curve shows less thermal stability in terms of their initial weight loss. However, in an oxygen atmosphere at about 700°C, the series of PAI–siloxane composites indicated a significant increase in char concentration. In the end, PAI with a relevant amount of silane groups was improved in both toughness and surface properties. This experiment showed that PDMS added to PAI had better properties than those of classical materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1774–1783, 2004     

Oxygen microwave plasma treatment of silicone elastomer: Kinetic behavior and surface composition

Silicone elastomers were surface modified by oxygen microwave plasma under different conditions and the elemental composition was followed by X‐ray photoelectron spectroscopy (XPS). The changes in elemental composition were mapped by a method based on ternary XPS diagrams that we have recently developed. Already at the shortest treatment times, 5 s, the change in surface composition is more than one‐half the maximum change obtained on prolonged exposure. After this initial change, the surface gradually oxidizes toward the final composition. Curve resolutions of C1s and Si2p XPS data showed that the initial jump in surface composition is caused by an oxidation of silicon where one of the two methyl groups are replaced by an oxygen. The second methyl group appears to be more difficult to remove, but as the treatment progresses, the number of oxygen bonded to silicon gradually increases. The dominating form of carbon acts as unoxidized methyl groups throughout the process, but the total carbon percentage decreases as the treatment progresses. This indicates either that the methyl groups are removed without prior oxidation or that the methyl groups are removed shortly after oxidation. A silica‐like surface layer was formed on prolonged plasma treatment under all the investigated conditions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 4098–4104, 2004     

有机硅副产高沸物的催化裂解及技术经济份析

本文简述了国内外高沸物催化裂解技术(综合利用)简况,着重阐述了本公司工业化开发成果,指出了该项开发的技术经济利益并提出适当建议。