Toughening of epoxy resin using acrylate‐based liquid rubbers

Carboxyl‐terminated poly(2‐ethylhexyl acrylate) (CTPEHA) liquid rubbers of different molecular weights and functionalities (LR‐1 to LR‐6) were synthesized by bulk and solution polymerization techniques. The liquid rubbers were characterized by nonaqueous titration, vapor pressure osmometry, and gel permeation chromatography. The CTPEHA oligomers were prereacted with the epoxy resin, and the modified epoxy networks were made by curing with an ambient‐temperature curing agent. The impact properties of the modified epoxy networks were evaluated, and the effects of molecular weight, functionality of the liquid rubber, and ductility of the matrix on the impact strength of the modified networks were investigated. The morphology of the toughening behavior was analyzed using a scanning electron microscope. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 716–723, 2000     

Amine-terminated polysulfone as modifier for epoxy resin

The synthesis of carboxyl-terminated poly(ethylene glycol adipate) (CTPA) and amine-terminated poly(amide sulfone) (ATPS) based on the CTPA and 4,4′-diaminodiphenyl sulfone (DDS) is described. The products were characterized by IR and ¹³C-NMR spectroscopic analysis, nonaqueous titration, viscosity measurement, and solubility characteristics. The developed ATPS was incorporated as a modifier into the epoxy matrix and its effect was studied by DSC and DMTA. It was found that ATPS forms a compatible blend with epoxy and imparts flexibility to the epoxy matrix. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:901–907, 1997     

Status of ceramic breeder pebble bed thermo-mechanics R&D and impact on breeder material mechanical strength

Among the international fusion solid breeder blanket community, there exists steady progress on the experimental, phenomenological, and numerical characterizations of the pebble bed effective thermo physical and mechanical properties, and of thermomechanic state of the bed under prototypical operating conditions. This paper summarizes recent achievements in pebble bed thermomechanics that were carried out by members of the IEA Fusion Nuclear Technology Subtask I Solid Breeding Blanket. A major goal is on developing predictive capability while identifying a pre-conditioned equilibrium stress state that would warrant pebble bed integrity during operations. The paper reviews and synthesizes existing computational modeling approaches for pebble bed thermomechanics prediction, and differentiating points of convergence/divergence among existing approaches. The progress toward modeling benchmark is also discussed. These advancements have led to a framework to help navigate future research.     

Studies on polyethylene oxide and phenolic resin blends

Blends of poly(ethylene oxide) (PEO) and novolac type phenolic resin were prepared by a solution cast method using acetonitrile as a solvent. In this work, we have investigated the PEO/phenolic blends having low phenolic content (0 to 30 wt %) with the objective in mind to design a crystallizable component for a shape memory polymer system having adjustable switching temperature. The blends were characterized by Fourier transform infrared (FTIR) spectroscopy, polarized optical microscopy (POM), and differential scanning calorimetry (DSC). The rate of crystallization and crystallinity (calculated from heat of crystallization value) decrease with increase in novolac content. FTIR analysis indicates the existence of H‐bonding between hydroxyl groups of novolac and ether groups of PEO. POM studies indicate that size of Maltese cross section decreases with increase in novolac content and in the blends containing higher novolac content less regular leaf like texture was obtained. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Sequestration of zinc from zinc oxide nanoparticles and life cycle effects in the sediment dweller amphipod Corophium volutator

We studied the effects of ZnO nanoparticles [ZnO NPs, primary particle size 35 ± 10 nm (circular diameter, TEM)], bulk [160 ± 81 nm (circular diameter, TEM)], and Zn ions (from ZnCl(2)) on mortality, growth, and reproductive endpoints in the sediment dwelling marine amphipod Corophium volutator over a complete lifecycle (100 days). ZnO NPs were characterized by size, aggregation, morphology, dissolution, and surface properties. ZnO NPs underwent aggregation and partial dissolution in the seawater exposure medium, resulting in a size distribution that ranged in size from discrete nanoparticles to the largest aggregate of several micrometers. Exposure via water to all forms of zinc in the range of 0.2-1.0 mg L(-1) delayed growth and affected the reproductive outcome of the exposed populations. STEM-EDX analysis was used to characterize insoluble zinc precipitates (sphaerites) of high sulfur content, which accumulated in the hepatopancreas following exposures. The elemental composition of the sphaerites did not differ for ZnO NP, Zn(2+), and bulk ZnO exposed organisms. These results provide an illustration of the comparable toxicity of Zn in bulk, soluble, and nanoscale forms on critical lifecycle parameters in a sediment dwelling organism.     

An Elastomeric Poly(Thiophene‐EDOT) Composite with a Dynamically Variable Permeability Towards Organic and Water Vapors

An interpenetrating polymer network (IPN) material with controllable nanoporosity is developed for applications such as chemical protection. The IPN material is based on a conducting polymer backbone consisting of thiophene and 3,4 ethylenedioxythiophene (EDOT) repeat units–poly(thiophene‐EDOT)–formed within a soft polyurethane support. The IPN demonstrates reversible, electrochemically switchable nanoporosity in the absence of standard liquid electrolyte, with the oxidized state being the open (high porosity) state and the reduced state being the closed (low porosity) state. The switching of the IPN between its oxidized (open) and reduced (closed) states is actuated using application of ±1.0 V. The variability in the IPN porosity, induced by the electrochemical switching, is revealed by large changes in water vapor diffusivity, as well as changes in the diffusivities of the chemical agent simulants chloroethyl ethyl sulfide (CEES) and methyl salicylate (MeS). The closed state of the IPN is able to decrease CEES diffusivity by ≈99% compared to expanded Teflon (ePTFE), while the open state allows high MVT rates comparable to ePTFE. The IPN's ability to allow high MVT under non‐threat conditions (open state) and high protection from agents under threat conditions (closed state) is a unique and desirable characteristic of this novel IPN material.     

In vitro antioxidant activity of different cultivars of banana flower (Musa paradicicus L.) extracts available in India

Abstract: Six different cultivars of banana flowers (Musa paradicicus) (Kathali, Bichi, Shingapuri, Kacha, Champa, and Kalabou) were analyzed for the content of polyphenol expressed as gallic acid equivalent and flavonoid expressed as quercetein equivalent, and the in vitro total antioxidative activities of the flower extracts were compared with standard and expressed as trolox equivalent. The reducing power, 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) and 2,2‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) radical cation (ABTS?⁺) scavenging activities, inhibition of lipid peroxidation in a linoleic acid emulsion system, and liposome peroxidation system were measured and compared with respective standard antioxidants. Iron‐mediated Fenton reaction was carried out to evaluate the protective effect of the extract of banana flower (Kacha cultivar) against H₂O₂‐induced DNA damage. The Kacha variety contains the maximum amount of polyphenol (11.94 ± 0.03 mg of gallic acid equivalent/g of dry weight) and flavonoid (0.174 ± 0.001 g of quercetin equivalent/g of polyphenol). It also has the highest total antioxidant capacity, DPPH radical scavenging activity, and ABTS?⁺ radical scavenging activity with a least EC₅₀ value of 0.051 mg/mL. Hepatic cell damage in iron‐mediated Fenton reaction caused by free radicals is reduced by the banana flower extract. On the basis of the results obtained, the banana flowers are found to be a potential source of natural antioxidants. This is the first report on the antioxidant properties of the extracts from banana flowers. The study suggests that the flowers of M. paradicicus that are found in India and consumed as vegetable can provide valuable functional ingredients that help in the prevention of oxidative stress.     

Influence of formic acid on electrochemical properties of high‐porosity Pt/TiN nanoparticle aggregates

Platinum‐deposited titanium nitride (Pt/TiN) nanoparticle aggregates with high porosities were successfully prepared via a self‐assembly‐assisted spray pyrolysis method. The addition of formic acid (HCOOH) had a significant influence on the process, promoting the simultaneous formation of metallic Pt and reduction on the surface of the TiN support material. Complete reduction of the Pt/TiN nanoparticle aggregates improved the catalytic activity. The electrochemical surface area (ECSA) of Pt/TiN with HCOOH (Pt/TiN_w/HCOOH) was 87.15 m²/g‐Pt, which was higher than that of Pt/TiN without HCOOH (Pt/TiN_w/o‐HCOOH). The catalytic durability of Pt/TiN_w/HCOOH was twice that of Pt/TiN_w/o‐HCOOH. An effective strategy for obtaining carbon‐free catalysts with high activities and durabilities was identified. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2753–2760, 2013