Synthesis and characterization of bisitaconimides. I

This article describes the synthesis and characterization of bisitaconimides on the basis of 4,4′‐diaminodiphenylether, 2,2′‐bis[4‐(4‐aminophenoxy)phenyl]propane, 1,3‐bis(4‐aminophenoxy)benzene, and 1,4‐bis (4‐aminophenoxy)benzene. Isomerization of the itaconimides to citraconimides (varying in the range of 25–40%) was observed during synthesis. The curing exotherm and thermal stability of the cured resins depended on the backbone structure of itaconimides. The curing exotherm immediately followed the melting endotherms. These resins cured at lower temperatures than bismaleimides but thermal stability of cured bismaleimides was higher than bisitaconimides. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2277–2282, 2002     

Synthesis and Biological Evaluation of Iodoglucoazomycin (I‐GAZ), an Azomycin–Glucose Adduct with Putative Applications in Diagnostic Imaging and Radiotherapy of Hypoxic Tumors

Iodoglucoazomycin (I‐GAZ; N‐(2‐iodo‐3‐(6‐O‐glucosyl)propyl)‐2‐nitroimidazole), a non‐glycosidic nitroimidazole–6‐O‐glucose adduct, was synthesized, radioiodinated, and evaluated as a substrate of glucose transporter 1 (GLUT1) for radiotheranostic (therapy+diagnostic) management of hypoxic tumors. Nucleophilic iodination of the nosylate synthon of I‐GAZ followed by deprotection afforded I‐GAZ in 74 % overall yield. I‐GAZ was radioiodinated via ‘exchange’ labeling using [^123/131I]iodide (50–70 % RCY) and then purified by Sep‐Pak? (>96 % RCP). [¹³¹I]I‐GAZ was stable in 2 % ethanolic solution in sterile water for 14 days when stored at 5 °C. In cell culture, I‐GAZ was found to be nontoxic to EMT‐6 cells at concentrations <0.5 mm , and weakly radiosensitizing (SER 1.1 at 10 % survival of EMT‐6 cells; 1.2 at 0.1 % survival in MCF‐7 cells). The hypoxic/normoxic uptake ratio of [¹²³I]I‐GAZ in EMT‐6 cells was 1.46 at 2 h, and under normoxic conditions the uptake of [¹²³I]I‐GAZ by EMT‐6 cells was unaltered in the presence of 5 mm glucose. The biodistribution of [¹³¹I]I‐GAZ in EMT‐6 tumor‐bearing Balb/c mice demonstrated rapid clearance from blood and extensive renal and hepatic excretion. Tumor/blood and tumor/muscle ratios reached ～3 and 8, respectively, at 4 h post‐injection. Regression analysis of the first order polynomial plots of the blood and tumor radioactivity concentrations supported a perfusion–excretion model with low hypoxia‐dependent binding. [¹³¹I]I‐GAZ was found to be stable in vivo, and did not deiodinate.     

Wettability and interfacial phenomena investigations on high-density polyethylene and petroleum coke

An in-depth wettability and interfacial phenomena investigation was carried out to study interactions between high density polyethylene (HDPE) and petroleum coke. The aim is to investigate the effect of temperature and contact times on possible interactions and adhesion characteristics for partially substituting coal-tar pitch binder with waste polymers. Using a sessile drop arrangement, experimental assemblies consisting of ground HDPE and a petroleum coke substrate were heat treated in the temperature range of 150–350°C for 15–60 min. Contact angles between molten HDPE and petroleum coke surface and depth of penetration of HDPE into petroleum coke substrate were measured. The highest contact angle (131.5°) was observed at 250°C after 15 min. and lowest contact angle (30.9°) was observed at 350°C after 60 min. Highest penetration depth (75 μm) was observed at 350°C after 60 min and lowest penetration (13 μm) at 200°C after 15 min. Analysis of results showed that increasing time and temperature of heat treatment had a significant impact on the interactions of molten HDPE with petroleum coke. Longer residence time and higher temperatures increased the extent of melting of HDPE, which in turn resulted in improved wettability and deeper penetration into petroleum coke substrate. HDPE was found to bind and adhere strongly with petroleum coke. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Flame retardants in building insulation: a case for re-evaluating building codes

US building codes balance the consideration of hazards to public safety, health and general welfare. Current codes require foam plastic insulation materials to have both protection by a thermal barrier and compliance with Steiner Tunnel test requirements. The Steiner Tunnel test is met by adding flame-retardant chemicals to the foam. Studies demonstrate that the Steiner Tunnel test does not give reliable fire safety results for foam plastic insulations. Foams that meet the Steiner Tunnel test still pose a fire hazard if used without a code-mandated thermal barrier. Insulations protected by a thermal barrier are fire safe and the use of flame retardants does not provide any additional benefit. Evidence is examined of the health and ecological impacts from the added flame-retardant chemicals. Changing the building codes could prevent health and environmental harm from the toxicity of these substances without a reduction in fire safety. Plastic foam insulations that are protected by a thermal barrier should be exempted from the Steiner Tunnel test and the need to use flame retardants. This change would align US codes with code regulations in Sweden and Norway and ensure the fire safety as well as improve health and environmental impacts.

Les codes de construction américains prennent en compte de manière équilibrée les dangers pour la sécurité publique, la santé et le bien-être général. Les codes actuels exigent que les matériaux d'isolation en mousse de plastique possèdent à la fois une protection assurée par une barrière thermique et une conformité aux exigences des tests en tunnel Steiner. Il est satisfait à l'essai en tunnel Steiner par l'ajout à la mousse de produits chimiques retardateurs de flamme. Les études démontrent que l'essai en tunnel Steiner ne donne pas de résultats fiables en matière de sécurité incendie concernant les isolations en mousse de plastique. Les mousses qui satisfont à cet essai présentent encore un risque incendie en cas d'utilisation sans une barrière thermique prescrite par un code. Les isolations protégées par une barrière thermique sont ignifuges et l'utilisation de retardateurs de flamme n'apporte aucun avantage supplémentaire. Sont examinés les éléments probants relatifs aux incidences sur la santé et l'environnement des produits chimiques retardateurs de flamme qui sont ajoutés. La modification des codes de construction pourrait prévenir les dommages en matière de santé et d'environnement dus à la toxicité de ces substances sans réduction de la sécurité incendie. Les isolations en mousse de plastique qui sont protégées par une barrière thermique devraient être dispensées de l'essai en tunnel Steiner et de la nécessité d'utiliser des retardateurs de flamme. Ce changement alignerait les codes américains sur les règles des codes en vigueur en Suède et en Norvège et garantirait la sécurité incendie tout en améliorant les incidences sur la santé et l'environnement.

Mots clés: codes de construction?sécurité incendie?retardateurs de flamme?inflammabilité?isolation?santé publique?Tunnel Steiner?barrière thermique?toxicité     

Copolymerization of methyl methacrylate with N-(methoxyphenyl) itaconimides

This article describes the synthesis and characterization of N-(3-methoxyphenyl) itaconimide (MAI) and N-(4-methoxyphenyl) itaconimide (PAI) obtained by the reaction of itaconic anhydride with m-anisidine and p-anisidine, respectively. Structural and thermal characterization of MAI and PAI monomers was performed with Fourier transform infrared (FTIR), ¹H-NMR, differential scanning calorimetry (DSC), and thermogravimetric analysis. Copolymerization of methyl methacrylate (MMA) with various amounts of MAI or PAI ranging from 0.1 to 0.5 was performed in solution with azobisisobutyronitrile as an initiator. Structural and molecular characterization of copolymers was performed with FTIR, ¹H-NMR, elemental analysis, and gel permeation chromatography. The nitrogen percentage was used to calculate the copolymer composition. The monomer reactivity ratios for MMA–MAI copolymers were found to be 1.00 ± 0.01 for MMA and 0.99 ± 0.07 for MAI; those for MMA–PAI copolymers were 0.93 ± 0.02 for MMA and 1.11 ± 0.10 for PAI. The molecular weights of the copolymers were in the range of 0.94–9.7 × 10³ (number-average molecular weight) and 3.3–101.8 × 10³ (weight-average molecular weight), with polydispersity indices in the range of 1.5–4.1. The molecular weight decreased with the increasing molar fraction of imide in the polymer backbone. The glass-transition temperature, as determined from DSC scans, increased with increasing amounts of itaconimides in the copolymers. A significant improvement in the char yield, as determined by thermogravimetry, was observed upon copolymerization. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of functionality of polyhedral oligomeric silsesquioxane [POSS] on the properties of sulfonated poly(ether ether ketone) [SPEEK] based hybrid nanocomposite proton exchange membranes for fuel cell applications

Organic–inorganic hybrid nanocomposite membranes were prepared using three different types of POSS i.e., PEG POSS^® cage mixture (PPOSS), trisilanol phenyl POSS^® (TSP POSS) and trisulfonic acid isobutyl POSS^® (SPOSS) at a fixed loading of 2% (w/w) as filler and SPEEK with degree of sulfonation (DS) 55% as polymer matrix. The influence of POSS functionality on hybrid membrane's thermo-mechanical properties, morphology, water uptake and proton conductivity was investigated. Thermal and mechanical stability of hybrid membranes increased upon incorporation of POSS. The size and distribution of POSS particles into SPEEK matrix was studied using transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) and it was found that TSP POSS and PPOSS based membranes showed smaller particle size and uniform distribution as compared to SPOSS based membranes which consequently affect the water uptake and proton conductivity of these hybrid membranes. The water uptake studies were carried out at three different temperatures i.e. 30, 80, 100 °C for 24 h and POSS based composite membranes showed higher water uptake and proton conductivity compared to neat SPEEK membranes. The highest proton conductivity (64.6 mS/cm) was observed for TSP POSS containing membrane which is more than double of neat SPEEK (31.3 mS/cm) membrane. The composite membrane containing TSP POSS can be considered as suitable membrane for PEMFCs applications.     

Schlegel description of grain form evolution in grain growth

The paths of evolution of topological grain forms during grain growth are described in terms of number of faces, edges per face and face arrangements, as depicted by Schlegel diagrams and the topological events that change them. This “Schlegel tree” describes transitions to higher face classes by grain encounters at corners and to lower face classes by grain-pair separation at three-edged faces. Transitions within face classes are described through rearrangements that occur to neighboring grains during these events. The process is further described by probabilities of the different paths in terms of numbers of edges, corners and three-edged faces at which face gain and loss events occur. Schlegel data from separated grains and three-dimensional Monte Carlo and front-tracking simulations show good comparison. Grain form frequencies increase with increasing number of transition paths into them from other forms. The highest frequency forms have few or no three-edged faces, while those with the most three-edged faces are present the least. These observations suggest that three-edged faces are catalysts for topological change, and forms with higher frequencies of these have shorter residence times before transitioning to lower classes.     

Simultaneous Decarburization and Oxidation Reactions Occurring in Silicon and Ferrosilicon Alloys at 1823 K

We present high temperature investigations on ferrosilicon alloys (Si: 24.7, 74, and 98.5%); silicon oxidation and decarburization studies in steelmaking have generally been limited to Fe‐based alloys containing up to 3.5 wt% Si. The effect of alloy composition, oxygen partial pressure and gas flow rate on interactions at 1823 K is evaluated. Decarburization and silicon oxidation reactions were found to occur simultaneously with significant differences observed in the weight gain and carbon loss. The net weight gain in these alloys was found to be due to the combined influence of decarburization (weight loss due to the generation of a gaseous product) and silicon oxidation (weight gain due to silica formation on the sample surface). There was a clear evidence for two rate regimes: the rate of decarburization was found to be much higher during the initial 2 min and a much slower rate was observed in later stages for all specimens. These rate regimes are explained in terms of the extent of surface coverage with the reaction product silica. No significant effect was found on the decarburization rates when the proportion of oxidizing gas (CO₂) was increased from 20 to 100%. The outcomes of this investigation will assist with the development of mechanisms governing the reactions of molten ferrosilicon and silicon alloys during their interactions with gaseous phases in the cupola process.     

Thermal behavior of graft copolymers of cotton cellulose and acrylate monomers

Cotton cellulose yarn was grafted with methyl acrylate, ethyl acrylate, n-butyl acrylate, and methyl methacrylate at various percentages of grafting. The effects of concentration of the initiator, concentration of the acid, and of temperature on grafting was studied and the mechanism discussed. The effect of reactivity of the monomer on the percentage graft-on is pointed out. Thermal behavior of natural and grafted cotton yarn was studied using dynamic thermogravimetry in air at a heating rate of 6°C/min up to a temperature of 500°C. The thermal stabilities of the samples grafted with various acrylate monomers to various percentages of grafting were computed from their primary thermograms by calculating the values of IDT, IPDT, and E^*. The results show that the thermal stability increases with increase in graft-on per cent, and the thermal stabilities of natural cotton and cotton grafted with different monomers are in the order ethyl > methyl > natural cellulose > methyl methacrylate > n-butyl acrylate.