Combined Effects of Silica Filler and Its Interface in Epoxy Resin

In this paper, mechanical properties of silica-filled epoxy resin are tested. The tests show that at elevated temperatures, the material’s properties (e.g. yield stress, flow stress, etc.) vary immonotonically with filler volume fraction. Nanoindentation test results suggest that an interface region, stronger than the matrix, is formed in the materials. The formation of the interface has positive effects on the yield strengths of materials. The addition of particles in the matrix produces a large disturbance in stress distribution, leading to stress concentration in the matrix. The stress concentration has negative effects on the yield strengths of materials. The calculation demonstrates that the maximum stress in samples varies immonotonically with particulate concentration. So, the immonotonic variation of mechanical behavior of materials may be rooted in the contradictory effects of the interface region and the stress concentration caused by particulate addition.

Micro- and macroscopic characterizations of the viscoelastic fracture of resin-based fibre composites

Micro- and macroscopic characterizations of the viscoelastic fracture of a unidirectional carbon-fibre-reinforced epoxy composite are presented. First, the micro-cracking behavior of the material is studied by the use of scanning electron microscopy; the in situ creep cracking process is observed and the crack propagation is measured. In order to obtain insight into the mechanisms of the observed creep cracking, macroscopic investigations were also carried out. Finite-element method simulations were carried out to calculate the stress distribution and the variation of stresses with time. A theoretical analysis of the orthotropy of viscoelastic fracture behavior of the material is also conducted.

Tailoring The Mechanical Performance Of Epoxy Resin By Various Nanoparticles

Flexible organic elastomeric nanoparticles (ENP) and two kinds of rigid inorganic silica nanoparticles were dispersed respectively into a bisphenol-A epoxy resin in order to tailor and compare the performance of mechanical properties. It was found that the well-dispersed flexible ENP greatly enhanced the toughness of the epoxy with the cost of modulus and strength. Comparatively, the rigid silica nanoparticles improved Young's modulus, tensile strength and fracture toughness simultaneously. Both fumed and sol-gel-formed nanosilica particles conducted similar results in reinforcing the epoxy resin, although the latter exhibited almost perfect nanoparticle dispersion in matrix. The toughening mechanisms of nanocomposites were further discussed based on fractographic analysis.

Hydrodynamics in an expanded bed of large size ion-exchange resin, and natural product adsorption

Successful applications of expanded bed adsorption (EBA) technology have been widely reported in the literature for protein purification. Little has been reported on the recovery of natural products and active components of Chinese herbal preparations using EBA technology. In this study, the hydrodynamic behavior in an expanded bed of cation resin, 001 x 7 Styrene-DVB, was investigated. Ephedrine hydrochloride (EH) was used as a model natural product to test the dynamic binding capacity (DBC) in the expanded bed. EBA of EH directly from a feedstock containing powdered herbs has also been investigated. These particles are different from commercially available expanded bed adsorbents by virtue of their large size (20S to 1030 gm). When the adsorbent bed is expanded to approximately 1.3 to 1.5 times its settled bed height, the axial liquid-phase dispersion coefficient was found to be of the order 10(-5) m(2) s(-1), which falls into the range 1.0 x 10(-6) to 1.0 X 10(-5) m(2) s(-1) observed previously in protein purification. Because of the favorable column efficiency (low axial dispersion coefficient), the recovery yield and purification factor values of EH directly from a feedstock reached 86.5% and 18, respectively. The results suggest that EBA technology holds promise for the recovery of natural products and active components of Chinese herbal preparations.

Production of biodiesel from soapstock using an ion-exchange resin catalyst

The feasibility of biodiesel production from soapstock containing high water content and fatty matters by a solid acid catalyst was investigated. Soapstock was converted to high-acid acid oil (HAAO) by the hydrolysis by KOH and the acidulation by sulfuric acid. The acid value of soapstock-HAAO increased to 199.1 mg KOH/g but a large amount of potassium sulfate was produced. To resolve the formation of potassium sulfate, acid oil was extracted from soapstock and was converted to HAAO by using sodium dodecyl benzene sulfonate (SDBS). The maximum acid value of acid oil-HAAO was 194.2 mg KOH/g when the mass ratio of acid oil, sulfuric acid, and water was 10:4:10 at 2% of SDBS. In the esterification of HAAO using Amberylst-15, fatty acid methyl ester (FAME) concentration was 91.7 and 81.3% for soapstock and acid oil, respectively. After the distillation, FAME concentration became 98.1% and 96.7% for soapstock and acid oil. The distillation process decreased the total glycerin and the acid value of FAME produced a little.

Enhancements of the simulation method on the edge effect in resin transfer molding processes

In resin transfer molding processes, small clearances exist between the fiber preform and the mold edges, which result in a preferential resin flow in the edge channel and then disrupt the flow patterns during the mold filling stage. A mathematical model including the effect of cavity thickness on resin flow was developed for flow behavior involving the interface between an edge channel and a porous medium. According to the mathematical analysis of momentum equations in a fully developed rectangular duct and formulations of the equivalent edge permeability, comparing with three-dimensional Navier-Stokes equations, the governing equations were modified in the edge channel. The volume of fluid (VOF) method was applied to track the flow front. A simple case is numerically simulated using the modified governing equations. The effects of edge channel width and cavity thickness on flow front and inlet pressure are analyzed, and the evolution characteristics of simulated results are in agreement with the experimental results. (c) 2007 Elsevier B.V. All rights reserved

The solid-liquid extraction of yttrium from rare earths by solvent (ionic liquid) impreganated resin coupled with complexing method

A kind of solvent (ionic liquid) impreganated resin (IL-SIR) was developed herein for ameliorating imidazolium-type IL-based liquid-liquid extraction of metal ions. In this study, [C(8)mim][PF6] containing Cyanex923 was immobilized on XAD-7 resin for solid-liquid extraction of rare earth (RE). The solid-liquid extraction contributed to ameliorating mass transfer efficiency, i.e. shortening equilibrium time from 40 min to 20 min, increasing extraction efficiency from 29% to 80%. In additional, the novel IL-SIR could separate Y(III) from Sc(III), Ho(III), Er(III), Yb(III) effectively by adding water-soluble complexing agent.

Polymerization of ethylene to branched polyethylene with silica and Merrifield resin supported nickel(II) catalysts with alpha-diimine ligands

Silica and Merrifield resin were used as carriers for the support of alpha-diimine nickel(II) precatalysts for ethylene polymerization. The alpha-diimine ligands containing allyl were modified by introducing the reactive Si-Cl end-group, allowing their immobilization via a direct reaction of the Si-Cl groups with the silanols on silica surface or the hydroxyls on the ethanolamine-modified Merrifield resin. The resulting supported alpha-diimine ligands were characterized by analytical and spectroscopic techniques (NMR and Fr-IR).

Reactive Mold Filling in Resin Transfer Molding Processes with Edge Effects

Reactive mold filling is one of the important stages in resin transfer molding processes, in which resin curing and edge effects are important characteristics. On the basis of previous work, volume-averaging momentum equations involving viscous and inertia terms were adopted to describe the resin flow in fiber preform, and modified governing equations derived from the Navier-Stokes equations are introduced to describe the resin flow in the edge channel. A dual-Arrhenius viscosity model is newly introduced to describe the chemorheological behavior of a modified bismaleimide resin. The influence of the curing reaction and processing parameters on the resin flow patterns was investigated.

WETTABILITY OF EPOXY RESIN ON CARBON FIBER

The micrographs of epoxy resin on single carbon fiber at room temperature and the temperature dependent contact angle on single carbon fiber were investigated using field environmental scanning electron microscope (FESEM). The results showed that the contact angle decreases significantly with increasing temperature. The advantage of this experimental approach was that can directly reflected the wettability of epoxy resin to fiber. But the experimental process was complicated, and there were many influence factors. The reason is that the wettability of epoxy resin on parallel sheet can be improved at higher temperatures. The spreading procedures for the epoxy resin droplet on carbon fiber cluster were observed by means of drop shape analysis system ( DSA) in parallel and perpendicular directions of the aligned fibers.

Solvent impregnated resin prepared using task-specific ionic liquids for rare earth separation

A novel bifunctional task-specific ionic liquid (TSIL), i.e. [trialkylmethylammonium][sec-nonylphenoxy acetate] ([A336] [CA-100]) was impregnated on intermediate polarized XAD-7 resin, and the prepared solvent impreganated resin (SIR) was studied for rare earth (RE) separation. Adsorption ability of the SIR was indicated to be obviously higher than that prepared by [A336][NO3] because of the functional anion of [A336][CA-100]. Adsorption kinetics, adsorption isotherm, separation and desorption of the SIR were also studied.

Convenient preparation of tunably loaded chemically converted graphene oxide/epoxy resin nanocomposites from graphene oxide sheets through two-phase extraction

We report a facile method to create the chemically converted graphene oxide/epoxy resin nanocomposites from graphene oxide sheets through two-phase extraction. Great improvements in mechanical properties such as compressive failure strength and toughness have been achieved for the chemically converted graphene oxide/epoxy resin for a 0.0375 wt% loading of chemically converted graphene oxide sheets in epoxy resin by 48.3% and 1185.2%, respectively. In addition, the loading of graphene is also conveniently tunable even to 0.15 wt% just by increasing the volume of the graphene oxide dispersion.

Characterization of the Microstructure of Bimodal HDPE Resin

In this work, two industrial bimodal high density polyethylene resins, resin A and resin B having similar molecular weight (M-w), molecular weight distribution (M-wD), and short-chain branching (SCB) content but different mechanical properties, were fractionated through cross-fractionation. The fractions were further, characterized by GPC, C-13 NMR, DSC AND FT IR techniques. These two resins were firstly fractionated into two franctions, i.e. high-temperature and low temperature fractions, via preparative solution crystallization fractionation. Resin A with much better mechanical properties contains more high-temperature fractions with longer crystalizable sequences. The SCB content in the low temperature fraction of resin A is lower than the of resin B. Both low-temperature fractions were then further fractionated using solvent gradient fractionation (SGF). The characterization of SGF fraction indicates that most of the branches fall into the high molecular weight chain in both low-temperature fractions.