Kinetic studies of the decomposition of flame retardant containing high-impact polystyrene

The thermal decomposition of flame retardant free high-impact polystyrene (HIPS) and four HIPS samples containing brominated flame retardants has been studied using TGA at different heating rates between 2.5 and 10 K min⁻¹. Decabromodiphenyl ether (DPE) and decabromodibenzyl (DDB) were used as flame retardants, and two of the samples contained antimony trioxide (Sb₂O₃) synergist besides the brominated additives. The activation energies (E_A) and frequency factors (k₀) were calculated by the methods of Kissinger and Ozawa. A compensation effect was observed and used for the identification of changes in the degradation kinetics. In a third step, the kinetic model of the reaction was determined. Both Kissinger and Ozawa showed that the HIPS degraded with an E_A of 200 kJ mol⁻¹. The choice of the flame retardant had, however, little impact on the TGA plot. The addition of a flame retardant as well as the addition of Sb₂O₃ reduced the E_A. Fire retardant free HIPS degraded mainly by power-law kinetics, while the addition of a flame retardant caused the mechanism to change to a phase-boundary controlled mechanism after a weight loss of 80 wt%.     

Synthesis and Characterization of Gelatin-Siloxane Hybrids Derived through Sol-Gel Procedure

A new type of inorganic-organic hybrid materials incorporating gelatin and 3-(glycidoxypropyl) trimethoxysilane (GPSM) was prepared through sol-gel processing. A solid-state ²⁹Si NMR analysis indicated that all the methoxy silane groups of GPSM were polymerized to yield —Si—O—Si— bridging bonds. An amino acid analysis confirmed grafting reactions of GPSM against gelatin chains. The increasing GPSM/gelatin ratio stimulated gel formation, phase separation, and the density of GPSM-crosslinking of the gelatin chains as well as it changed the micro- and macro- structures and the viscoelastic properties of the final products.     

Carbon–carbon bond formation via benzoyl umpolung attained by photoinduced electron-transfer with benzimidazolines

A photoreaction between benzoyl compounds, such as benzoylformate derivatives, and 2-(p-anisyl)-1,3-dimethylbenzimidazoline in the presence of allyl bromide was found to give various allylated alcohols. In the reaction of benzoylformates, α-hydroxy ester enolates, for which the negative charge occurs on the carbonyl carbon of benzoyl (umpolung reactivity), are proposed to be generated as intermediates by electron-transfer from benzimidazolines to the photoexcited benzoylformates; these species react with allyl bromide to produce α-allyl-α-hydroxy esters.     

Wet deposition of titania-apatite composite in cotton fibrils

Titania consisting of rutile and anatase was precipitated on and inside of cotton fibrils when cotton was soaked in an aqueous solution of 30 mM TiOSO₄ and 30 mM H₂O₂ kept at 80°C for 24 h. As the resultant titania-cotton fibrils were soaked in a simulated body fluid (Kokubo solution), apatite was deposited on the fibrils to yield cotton-titania-apatite composites within 1 d. Thus, the present study provided a simple technique to prepare titania-apatite composites and coatings on organic materials at low temperature. Presented at the Sol-gel 2005 in Los Angeles     

Low‐CTE photosensitive polyimide based on semialicyclic poly(amic acid) and photobase generator

A negative‐type photosensitive polyimide (PSPI) based on semialicyclic poly(amic acid) (PAA), poly(trans‐1,4‐cyclohexylenediphenylene amic acid), and {[(4,5‐dimethoxy‐2‐nitrobenzyl)oxy]carbonyl} 2,6‐dimethylpiperidine (DNCDP) as a photobase generator has been developed as a next‐generation buffer coat material. The semialicyclic PAA was synthesized from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and trans‐1,4‐cyclohexyldiamine in the presence of acetic acid, and the PAA polymerization solution was directly used for PSPI formulation. This PSPI, consisting of PAA (80 wt %) and DNCDP (20 wt %), showed high sensitivity of 70 mJ/cm² and high contrast of 10.3, when it was exposed to a 365‐nm line (i‐line), postexposure baked at 190 °C for 5 min, and developed with 2.38 wt % tetramethylammonium hydroxide aqueous solution containing 20 wt % isopropanol at 25 °C. A clear negative image of 6‐μm line and space pattern was printed on a film, which was exposed to 500 mJ/cm² of i‐line by a contact printing mode and fully converted to poly(trans‐1,4‐cyclohexylenebiphenylene imide) pattern upon heating at 250 °C for 1 h. The PSPI film had a low coefficient of thermal expansion of 16 ppm/K compared to typical PIs, such as prepared from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and 4,4′‐oxydianiline. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1317–1323, 2010     

Adoption of a genetic algorithm (GA) for tomographic reconstruction of line-of-sight optical images

 A new tomographic reconstruction scheme is proposed that uses a genetic algorithm (GA), a robust and combinatorial function optimization based on the mechanics of the genetic principle. The paper first discusses the implicitly parallel and scaled random nature of the GA optimization using an illustrative example. An introduction of the elementary distribution function (EDF) to constitute the cross-sectional field shows a successful adoption of GA for optical tomography. The GA-based tomography was examined for interferometric projections of computer-synthesized phantom density fields. The GA-based tomography shows accurate and stable image reconstruction, particularly for limited projections. Received: 6 November 1995 / Accepted: 6 May 1996     

Study of theω π + system

The mass spectra of theω π ⁰ system, produced inπ ^? p charge-exchange reactions at 38 GeV/c and 100 GeV/c, show a new neutral state with a mass of 2200±20 MeV and a width of 260±50 MeV. Likeρ ₃(1690), this meson,X(2200), is produced through one-pion-exchange.X(2200)J ^PC is likely 1^??. It might be a 2³ D ₁ radial-orbital excitation ofρ ⁰. Its production cross section falls with energy quadratically, in agreement with one-pion-exchange. The cross sections forb ₁(1235) andρ ₃(1690) production have also been measured; their energy dependences have been determined.     

Asymmetric α-2-tosylethenylation of N,N-dialkyl-L-amino acid esters via the formation of non-racemic ammonium enolates

Asymmetric α-2-tosylethenylation of (S)-2-(pyrrolidin-1-yl)propanoic acid esters was shown to produce good yields with high enantioselectivities. The reaction proceeds via the formation of a non-racemic ammonium enolate without an external source of chirality.     

Bipolar reverse osmosis membrane for separating mono-and divalent ions

Bipolar reverse osmosis membranes that have both negatively and positively charged layers have been prepared to enhance the selectivity towards mono- and divalent ions in respect of both cations and anions. Positively charged layers are formed on low pressure reverse osmosis membranes having negative charge (NTR-7410 and 7450) by an adsorption method using polyethyleneimine (PEI) or a quaternary ammonium polyelectrolyte (QAP). These layers attach to the membrane's dense layer, which is made of sulfonated polyether sulfone. The selectivity of mono- and divalent ions is proven by experimental results for single electrolytes (NaCl, Na₂SO₄ and MgCl₂). Although negatively charged membranes repulse divalent anions more strongly than cations and monovalent anions, bipolar reverse osmosis membranes reject both divalent cations and divalent anions better than monovalent ions. An optimal preparation method for bipolar membranes showing selectivity towards mono- and divalent ions were developed. The bipolar membranes showed good ion selectivity for artificial sea water.     

Light scattering properties of a rough-ended optical fibre

Uniform wide-angle irradiation of a laser beam is achieved by roughening chemically the output end of an optical fibre. The angular distribution of the scattered light is analysed experimentally as a function of the incident angle of the laser beam into the input end of the fibre and the length of the rough core surface at its output end.