Resin Suspensions Research Articles

Highly Concentrated Hydroxyapatite Suspension for DLP Printing

Due to the lack of commercially available high-quality hydroxyapatite (HA) powder, it is still rarely reported by the literature concerning the development of UV resin for digital light processing 3D printing. The previous studies still had the problem of delamination and also poor sintering performance led by low solid-load slurry. Here low viscosity and high solid-load hydroxyapatite (HA) UV resin suspensions were developed for digital light processing 3D printing. In this study, the effect of the type of dispersant, the dose levels of dispersant and the solid load of HA powder on the rheology properties were thoroughly investigated to obtain a flowable highly-concentrated HA UV resin suspension. Finally, a 40vol% slurry with viscosity of 3.7Pa·s at a shear rate of 10 s-1 was successfully developed. After 3D printing and sintering, a dense ceramic with relative density of 95.85% can be obtained at a sintering temperature of 1300°C.

Photopolymerization of acrylate resin and ceramic suspensions with benzylidene ketones under blue/green LED

Finding novel photoinitiators with photobleaching properties suitable for long-wavelength LED light sources is important for their potential use in the photocuring ceramic suspensions containing acrylate resin. Two D-π-A-π-D conjugated benzylidene ketones with visible light absorption (TPAK and CZK) were synthesized and evaluated as photoinitiators in the photocuring of acrylate resin and ceramic suspension under blue (460 nm)/green (520 nm) LED sources. Results showed that the two photoinitiators have high photoinitiating activity and can effectively produce thick-layer curing in acrylate resin and ceramic suspension due to their quick photobleaching properties under 460 nm and 520 nm LED light sources. The curing depth of the ceramic suspensions was measured as a function of the concentration of TPAK and CZK and the energy level of the LED light source. Jacob's equation was used to determine the critical energy Ec and depth sensitivity Dp of every suspension with different concentrations of benzylidene ketones.

Stress mechanisms acting during the dispersing in highly viscous media and their impact on the production of nanoparticle composites

Nanoparticle reinforced fibre composites promise enhanced product properties demanded for many fields of application. However, the targeted production of nanoparticle resin suspensions is demanding and requires detailed knowledge about the fundamental mechanisms acting during the process. In order to obtain this knowledge, the dispersing process of nanoparticle-suspensions with high viscosities is investigated by the example of epoxy resin — alumina suspensions which are used as a matrix material for fiber reinforced plastics. The performance of several dispersing machines with differing stress mechanisms is compared and dependencies on process parameters are characterized. Laminar shear flow dispersing was performed in a three roller mill as well as in a kneader. In a pin-counter-pin stirred media mill and a basket mill dispersing between grinding media surfaces was investigated. The effect of process parameters on the stress energy/intensity and its effect on the product quality was studied for the respective stress mechanisms with special focus on the impact of suspension viscosity. An existing model to quantify the stress acting in laminar shear flow is extended to account for the influence of solids content utilizing the concept of shear stress equivalent shear rates. Deviations from commonly known dependencies of dispersing processes with grinding media are found and explained by a change in the governing stress mechanism which depends on the viscosity and particle size of the suspension. Process maps for the dispersing in highly viscous media are derived regarding desired particle size, energy efficiency and required solids content for the respective machines.

A fundamental investigation of the surfactant-stabilized single-walled carbon nanotube/epoxy resin suspensions by molecular dynamics simulation

The surfactant-assisted stabilization of single-walled carbon nanotubes (SWCNTs) in SWCNT/epoxy resin suspensions were investigated for different surfactant types, concentrations, and temperatures using molecular dynamics simulation. One cationic surfactant, i.e. cetyltrimethylammonium bromide (CTAB), and three anionic surfactants, i.e. sodium dodecyl sulfate (SDS), sodium dodecylbenzenesulfonate (NaDDBS), and sodium cholate (SC), as well as a 1:1 mixture of CTAB and SDS were used. Potentials of mean force (PMFs) were generated between two fixed-size (6,6) SWCNTs for all neat (no surfactant) and surfactant-loaded SWCNT/epoxy resin systems at three different surfactant concentrations (0.25, 0.50, and 1.00 wt%) at room (298 K) and elevated temperature (398 K, only for low-surfactant-concentration systems). Overall, two distinct mechanisms of SWCNT stabilization by the surfactants were identified: (1) an increase in the SWCNT aggregation energy barrier due to the wrapping of the SWCNTs by the surfactant molecules, and (2) a constantly positive free energy (repulsion) for all SWCNT separation distances due to the encapsulation of the two approaching SWCNTs. With the second mechanism, there is a delay for the epoxy molecules to be pushed out from the space between the two SWCNTs. With an increase in the surfactant concentration, the first mechanism becomes more prevalent. With an increase in temperature to 398 K, all surfactants migrate to the suspending medium, thereby the second mechanism of SWCNT stabilization dominates. A drop in the SWCNT-surfactant binding energy is observed around 360–370 K, signifying the surfactant migration to the suspending medium. More or less, all surfactants stabilize the SWCNTs in an epoxy resin at one or more surfactant concentrations. However, NaDDBS exhibits a higher SWCNT aggregation barrier at high concentrations and both temperatures (298 K and 398 K), thereby providing a better SWCNT stabilization in the epoxy resin compared to the other surfactants.

Microfluidization, time-effective and solvent free processing of nanoparticle containing thermosetting matrix resin suspensions for producing composites with enhanced thermal properties

Dispersion of low content (0.1wt.%) of multi walled carbon nanotubes (MWCNTs) in an epoxy resin through microfluidization was brought under spotlight as a case study. For the sake of performance comparison, epoxy resin suspension with the same MWCNT content was also produced through sonication, and the energy consumed to disperse MWCNTs in the epoxy resin remained the same for the both processes. At the equal energy consumption level, preparing the resin suspension through microfluidization was determined to take approximately 4.5min, which is about 9 times lower than it takes for the same suspension to be prepared through sonication. Following cure of the prepared suspensions, thermal and thermo-mechanical properties of the resulting composites were systematically investigated. As a result, glass transition temperature (Tg) of the neat epoxy and its composites produced by sonication and microfluidization were determined to be 78±3, 83±5 and 88±4°C, respectively. Moreover, thermal expansion coefficient (CTE) of the epoxy resin was reduced by 7% when it was blended with MWCNTs through microfluidization, while no significant change was observed in the corresponding CTE value when through sonication. Thermomechanical testing findings implied about 5% and 10% improvement in storage and loss modulus values of the composites produced by microfluidization over by sonication. Transmission electron microscopy (TEM) examination showed that MWCNTs were more homogenously and individually dispersed in the epoxy resin by retaining their initial aspect ratio through microfluidization. Scanning electron microscopy (SEM) examination revealed that composite fracture surface morphology significantly varied, depending to large extent on the type of the process used. Based on the results obtained, it was proposed that microfluidization might pave the way for cost-and-time effective solvent-free processing of nanoparticle modified thermosetting resin suspensions, especially including those that could be promisingly used as matrix constituent for manufacturing fabric reinforced composites with multi-functional properties.

Low viscosity processing using hybrid CNT-coated silica particles to form electrically conductive epoxy resin composites

Abstract Hybrid particles of multiwall carbon nanotubes (CNTs) grafted onto silica gel were shown to provide a low viscosity processing route to forming electrically-conductive epoxy resin composites. Rheological studies showed the viscoelastic shear moduli of epoxy resin suspensions containing these particles (named SG6_3) remained within the same order of magnitude as that of the neat resin at ≤5 wt% loading (containing up to 1.65 wt% of grafted CNTs). Whereas, the addition of 1.65 wt% of discrete (non-grafted) CNTs into the same resin increased shear moduli by up to seven orders of magnitude. The complex viscosities of suspensions containing ≤5 wt% of SG6_3 remained essentially unchanged, whereas an increase of up to five orders of magnitude resulted upon the addition of 1.65 wt% of non–grafted CNTs. Whilst rheological studies showed SG6_3 did not form a percolated network at levels ≤5 wt%, addition of only 2 wt% (containing 0.66 wt% CNT) was found to form an electrically–conductive percolated network in an epoxy resin composite with conductivity ∼ 10 −4 S/m.

Microfiltration of micro-sized suspensions of boron-selective resin with PVDF membranes

In this paper microfiltration (MF) separation of fractionized ion exchange Amberlite IRA743 resin from aqueous solutions using polyvinylidene fluoride membranes with the pore sizes of 0.1, 0.22 and 0.45μm was studies. The effect of membrane pore size, transmembrane pressure, pH and concentration of the resin suspensions, presence of NaCl, MgCl2 and Na2SO4 salts on permeate flux has been evaluated. It was shown that the dominant membrane fouling mechanism during MF of the resin suspensions is formation of a cake layer from deposited resin on the membrane surface. The flux declines with increasing operating pressure and suspension concentration, while it increases with the presence of inorganic salts and feed pH. Changes in zeta potential of resin particles and the membranes as well as agglomeration and electroviscous effects should be considered while analyzing these findings. It was shown that the resin particles after boron sorption can be efficiently regenerated and reused in combined adsorption-microfiltration (AMF) process of boron removal from water, however a sharp drop in membrane flux during MF separation of the resin suspension should be further addressed to develop the efficient AMF procedure.

Formation of functionalized nanoclusters by solvent evaporation and their effect on the physicochemical properties of dental composite resins

ObjectiveThe aim of this work was to study the effect of silica nanoclusters (SiNC), obtained by a solvent evaporation method and functionalized by 3-methacryloxypropyltrimethoxysilane (MPS) and MPS+octyltrimethoxysilane (OTMS) (50/50wt/wt), on the rheological, mechanical and sorption properties of urethane dimethylacrylate (UDMA)/triethylenglycol dimethacrylate (TEGDMA) (80/20wt/wt) resins blend. MethodsSilica nanoparticles (SiNP) were silanized with MPS or MPS+OTMS (50/50wt/wt) and incorporated in an UDMA-isopropanol mix to produce functionalized silica nanoclusters after evaporating the isopropanol. The effect of functionalized SiNC on resins rheological properties was determined by large and small deformation tests. Mechanical, thermal, sorption and solubility properties were evaluated for composite materials. ResultsThe UDMA/TEGDMA (80/20wt/wt) resins blend with added SiNC (ca. 350nm) and functionalized with MPS showed a Newtonian flow behavior associated to their spheroidal shape, whereas the resins blend with nanoclusters silanized with MPS+OTMS (50/50wt/wt) (ca. 400nm) showed a shear-thinning behavior due to nanoclusters irregular shape. Composite materials prepared with bare silica nanoclusters showed lower compressive strength than functionalized silica nanoclusters. MPS functionalized nanoclusters showed better mechanical properties but higher water sorption than functionalized nanoclusters with both silane coupling agents, MPS and OTMS. SignificanceThe solvent evaporation method applied to functionalized nanoparticles showed to be an alternative way to the sinterization method for producing nanoclusters, which improved some dental composite mechanical properties and reduced water sorption. The shape of functionalized silica nanoclusters showed to have influence on the rheological properties of SiNC resin suspensions and the mechanical and sorption properties of light cured composites.

Rheological behaviour of nanocellulose reinforced unsaturated polyester nanocomposites

Nanocellulose (NC) reinforced unsaturated polyester (UPR) composites were prepared by mechanical mixing process. Effect of isora nanocellulose on the properties of polyester composites has been studied in detail. Rheological properties of unsaturated polyester resin suspensions containing various amounts (0.5, 1 and 3wt%) of nanocellulose were investigated by oscillatory rheometer with parallel plate geometry. Analysis of curing revealed that the time required for gelation in NC filled UPR is lower than neat resin, which describe the catalytic action of NC on cure reaction. NC reinforced polyester suspensions showed shear thinning behaviour initially and at higher shear rates they showed Newtonian behaviour. Tensile and impact properties showed superior behaviour revealing improved interfacial bonding between nanofiller and the polymer matrix. With respect to the neat polyester the percentage increase in tensile strength of 0.5wt% NC reinforced composite is 57%. Optical and atomic force microscopic studies confirmed that the dispersion state of NC within the polyester matrix was adequate. Maximum glass transition temperature is obtained for 0.5wt% NC reinforced composite, which showed an increase of 10°C than neat resin.

Mechanical properties and fracture behaviors of epoxy composites with phase-separation formed liquid rubber and preformed powdered rubber nanoparticles: A comparative study

Epoxy composites filled with phase-separation formed submicron liquid rubber (LR) and preformed nanoscale powdered rubber (PR) particles were prepared at different filler loading levels. The effect of filler loading and type on the rheological properties of liquid epoxy resin suspensions and the thermal and mechanical properties of the cured composites as well as the relative fracture behaviors are systematically investigated. Almost unchanged tensile yield strength of the cured epoxy/PR composites is observed in the tensile test compared with that of the neat epoxy; while the strength of the cured epoxy/LR composites shows a maximum value at ∼4.5 wt% and significantly decreases with increasing LR content. The glass transition temperature (Tg) of the cured PR/epoxy has shifted to the higher temperature in the dynamic mechanical thermal analysis compared with that of the cured pure epoxy and epoxy/LR composites. Furthermore, the presence of LR results in highly improved critical stress intensity factor (KIC) of epoxy resin compared with the corresponding PR nanoparticles. In particular, the PR and LR particles at 9.2 wt% loading produce about 69 and 118% improvement in KIC of the epoxy composites, respectively. The fracture surface and damage zone analysis demonstrate that these two types of rubber particles induce different degrees of local plastic deformation of matrix initiated by their debonding/cavitation, which was also quantified and correlated with the fracture toughness of the two epoxy/rubber systems. POLYM. COMPOS., 36:785–799, 2015. © 2014 Society of Plastics Engineers

Effects of Epoxy Resin on Gelcasting Process and Mechanical Properties of Alumina Ceramics

A gelling system based on the polymerization of epoxy resin ethylene glycol diglycidyl ether (EGDGE) and 3,3′‐Diaminodipropylamine (DPTA) was developed for gelcasting alumina ceramics. The gelation process of 50 vol% alumina‐epoxy resin suspensions were investigated in accordance with the change in temperature and epoxy resin concentration. The activation energy Ea of polymerization reaction was 63.76 kJ/mol and no significant gelation was observed at 25°C during the test for 50 vol% Al2O3 suspensions with 10 wt% EGDGE. With the increase in EGDGE concentration, Al2O3 green bodies exhibited higher relative density, flexural strength, and Weibull modulus, reaching 64.4%, 41.03 MPa, and 12.51, respectively, when EGDGE concentration was 20 wt%. However, for sintered Al2O3 bodies, the highest characteristic strength and Weibull modulus were obtained for 15 wt% EGDGE concentration, reaching 367.57 MPa and 14.52, respectively.

Polyaniline Stabilized Magnetite Nanoparticle Reinforced Epoxy Nanocomposites

Magnetic epoxy polymer nanocomposites (PNCs) reinforced with magnetite (Fe(3)O(4)) nanoparticles (NPs) have been prepared at different particle loading levels. The particle surface functionality tuned by conductive polyaniline (PANI) is achieved via a surface initiated polymerization (SIP) approach. The effects of nanoparticle loading, surface functionality, and temperature on both the viscosity and storage/loss modulus of liquid epoxy resin suspensions and the physicochemical properties of the cured solid PNCs are systematically investigated. The glass transition temperature (T(g)) of the cured epoxy filled with the functionalized NPs has shifted to the higher temperature in the dynamic mechanical analysis (DMA) compared with that of the cured pure epoxy. Enhanced mechanical properties of the cured epoxy PNCs filled with the functionalized NPs are observed in the tensile test compared with that of the cured pure epoxy and cured epoxy PNCs filled with as-received NPs. The uniform NP distribution in the cured epoxy PNCs filled with functionalized NPs is observed by scanning electron microscope (SEM). These magnetic epoxy PNCs show the good magnetic properties and can be attached by a permanent magnet. Enhanced interfacial interaction between NPs and epoxy is revealed in the fracture surface analysis. The PNCs formation mechanism is also interpreted from the comprehensive analysis based on the TGA, DSC, and FTIR in this work.

Cure and Dynamic-Mechanical Behaviors of Vinyl Ester Resinfilled with Multi-Walled Carbon Nanotubes

The cure kinetics of Derakane 411-350, a kind of vinyl ester resin, and its suspensions containing multi-walled carbon nanotubes( MWCNTs) were investigated via non-isothermal dynamic scanning calorimetry (DSC) measurements. The results showed that incorporation of MWCNTs into vinyl ester resin excessively reduces polymerization degree and crosslinking density of vinyl ester resin. For suppressing the negative effect caused by nanotubes, the higher temperature initiator combined with the initiator MEKP was used. Dynamic-mechanical Behavior testing was then carried out on the cured sample in order to relate the curing behavior of MWCNTs modified resin suspensions to mechanical response of their resulting nanocomposites. It was revealed that nanocomposites containing MWCNTs possessed larger storage modulus values as well as higher glass transition temperatures (Tg) as compared to those without MWCNTs after using mixed intiators system to improve the degree of cure.

Electric field effects on CNTs/vinyl ester suspensions and the resulting electrical and thermal composite properties

In this study, electrical conductivity of a vinyl ester based composite containing low content (0.05, 0.1 and 0.3 wt.%) of double and multi-walled carbon nanotubes with and without amine functional groups (DWCNTs, MWCNTs, DWCNT-NH 2 and MWCNT-NH 2) was investigated. The composite with pristine MWCNTs was found to exhibit the highest electrical conductivity. Experiments aimed to induce an aligned conductive network with application of an alternating current (AC) electric field during cure were carried out on the resin suspensions with MWCNTs. Formation of electric anisotropy within the composite was verified. Light microscopy (LM), scanning electron (SEM) and transmission electron microscopy (TEM) were conducted to visualize dispersion state and the extent of alignment of MWCNTs within the polymer cured with and without application of the electric field. To gain a better understanding of electric field induced effects, glass transition temperature ( T g) of the composites was measured via Differential Scanning Calorimetry (DSC). It was determined that at 0.05 wt.% loading rate of MWCNTs, the composites, cured with application of the AC electric field, possessed a higher T g than the composites cured without application of the AC electric field.

Rheological behaviors and electrical conductivity of epoxy resin nanocomposites suspended with in-situ stabilized carbon nanofibers

Epoxy resin nanocomposites suspended with carbon nanofibers (CNFs) have been prepared. A bifunctional coupling agent, 3-aminopropyltriethoxysilane, is used to treat the acid oxidized fibers. The dispersion quality of the CNFs with and without surface modification is monitored by an oscillatory rheological investigation. The addition of fibers is observed to influence the rheological behaviors of the suspensions drastically. Newtonian fluid behavior disappears as the fiber loading increases. A significant increase of the complex viscosity and storage modulus is observed, especially when the temperature increases to 50 °C and 75 °C. In-situ reaction between the amine-terminated functional groups on the silanized fibers and the resin, is justified by the FT-IR analysis and is responsible for the improved fiber dispersion and network formation. A decreased rheological percolation is observed after silanization due to the improved fiber dispersion quality. The electrical conductivity percolation is well correlated to the rheological percolation for the as-received fiber resin suspensions. However, with an insulating organic coating on the fiber surface, the conductivity increases slightly and lacks the correlation to the rheological percolation.

Cure kinetics of vapor grown carbon nanofiber (VGCNF) modified epoxy resin suspensions and fracture toughness of their resulting nanocomposites

In this study, the cure kinetics of Cycom 977-20, an aerospace grade toughened epoxy resin, and its suspensions containing various amounts (1, 3 and 5 wt.%) of vapor grown carbon nanofibers (VGCNFs) with and without chemical treatment were monitored via dynamic and isothermal dynamic scanning calorimetry (DSC) measurements. For this purpose, VGCNFs were first oxidized in nitric acid and then functionalized with 3-glycidoxypropyltrimethoxy silane (GPTMS) coupling agent. Fourier transform infrared (FTIR) spectroscopy was subsequently used to verify the chemical functional groups grafted onto the surfaces of VGCNFs. Sonication technique was conducted to facilitate proper dispersion of as-received, acid treated and silanized VGCNFs within epoxy resin. Dynamic DSC measurements showed that silanized VGCNF modified resin suspensions exhibited higher heat of cure compared to those with as-received VGCNFs. Experimentally obtained isothermal DSC data was then correlated with Kamal phenomenological model. Based on the model predictions, it was found that silanized VGCNFs maximized the cure reaction rates at the very initial stage of the reaction. Accordingly, an optimized curing cycle was applied to harden resin suspensions. Fracture testing was then carried out on the cured samples in order to relate the curing behavior of VGCNF modified resin suspensions to mechanical response of their resulting nanocomposites. With addition of 1 wt.% of silanized VGCNFs, the fracture toughness value of neat epoxy was found to be improved by 12%. SEM was further employed to examine the fracture surfaces of the samples.

Thermal curing behavior of MWCNT modified vinyl ester‐polyester resin suspensions prepared with 3‐roll milling technique

AbstractThis study aims to investigate the curing behavior of a vinyl ester‐polyester resin suspensions containing 0.3 wt % of multiwalled carbon nanotubes with and without amine functional groups (MWCNTs and MWCNT‐NH2). For this purpose, various analytical techniques, including Differential Scanning Calorimetry (DSC), Fourier infrared spectroscopy (FTIR), Raman Spectroscopy, and Thermo Gravimetric Analyzer (TGA) were conducted. The resin suspensions with carbon nanotubes (CNTs) were prepared via 3‐roll milling technique. DSC measurements showed that resin suspensions containing CNTs exhibited higher heat of cure (Q), besides lower activation energy (Ea) when compared with neat resin. For the sake of simplicity of interpretation, FTIR investigations were performed on neat vinyl ester resin suspensions containing the same amount of CNTs as resin. As a result, the individual fractional conversion rates of styrene and vinyl ester were interestingly found to be altered dependent on MWCNTs and MWCNT‐NH2. The findings obtained from RS measurements of the cured samples are highly proportional to those obtained from FTIR measurements. TGA measurements revealed that CNT modified nanocomposites have higher activation energy of degradation (Ed) compared with the cured polymer. The findings obtained revealed that CNTs with and without amine functional groups alter overall thermal curing response of the surrounding matrix resin, which may probably impart distinctive characteristics to mechanical behavior of the corresponding nanocomposites achieved. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1511–1522, 2009

Tensile mechanical behavior and fracture toughness of MWCNT and DWCNT modified vinyl-ester/polyester hybrid nanocomposites produced by 3-roll milling

This study aims to investigate the tensile mechanical behavior and fracture toughness of vinyl-ester/polyester hybrid nanocomposites containing various types of nanofillers, including multi- and double-walled carbon nanotubes with and without amine functional groups (MWCNTs, DWCNTs, MWCNT-NH 2 and DWCNT-NH 2). To prepare the resin suspensions, very low contents (0.05, 0.1 and 0.3 wt.%) of carbon nanotubes (CNTs) were dispersed within a specially synthesized styrene-free polyester resin, conducting 3-roll milling technique. The collected resin stuff was subsequently blended with vinyl-ester via mechanical stirring to achieve final suspensions prior to polymerization. Nanocomposites containing MWCNTs and MWCNT-NH 2 were found to exhibit higher tensile strength and modulus as well as larger fracture toughness and fracture energy compared to neat hybrid polymer. However, incorporation of similar contents of DWCNTs and DWCNT-NH 2 into the hybrid resin did not reflect the same improvement in the corresponding mechanical properties. Furthermore, experimentally measured elastic moduli of the nanocomposites containing DWCNTs, DWCNT-NH 2, MWCNTs and MWCNT-NH 2 were fitted to Halphin–Tsai model. Regardless of amine functional groups or content of carbon nanotubes, MWCNT modified nanocomposites exhibited better agreement between the predicted and the measured elastic moduli values compared to nanocomposites with DWCNTs. Furthermore, Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) were used to reveal dispersion state of the carbon nanotubes within the hybrid polymer and to examine the CNT induced failure modes that occurred under mechanical loading, respectively. Based on the experimental findings obtained, it was emphasized that the types of CNTs and presence of amine functional groups on the surface of CNTs affects substantially the chemical interactions at the interface, thus tuning the ultimate mechanical performance of the resulting nanocomposites.

Rheological and dynamic-mechanical behavior of carbon nanotube/vinyl ester–polyester suspensions and their nanocomposites

Rheological properties of vinyl ester–polyester resin suspensions containing various amounts (0.05, 0.1 and 0.3 wt.%) of multi walled carbon nanotubes (MWCNT) with and without amine functional groups (–NH 2) were investigated by utilization of oscillatory rheometer with parallel plate geometry. Dispersion of corresponding carbon nanotubes within the resin blend was accomplished employing high shear mixing technique (3-roll milling). Based on the dynamic viscoelastic measurements, it was observed that at 0.3 wt.% of CNT loadings, storage modulus ( G′) values of suspensions containing MWCNTs and MWCNT–NH 2 exhibited frequency-independent pseudo solid like behavior especially at lower frequencies. Moreover, the loss modulus ( G″) values of the resin suspensions with respect to frequency were observed to increase with an increase in contents of CNTs within the resin blend. In addition, steady shear viscosity measurements implied that at each given loading rate, the resin suspensions demonstrated shear thinning behavior regardless of amine functional groups, while the neat resin blend was almost the Newtonian fluid. Furthermore, dynamic mechanical behavior of the nanocomposites achieved by polymerizing the resin blend suspensions with MWCNTs and MWCNT–NH 2 was investigated through dynamic mechanical thermal analyzer (DMTA). It was revealed that storage modulus ( E′) and the loss modulus ( E″) values of the resulting nanocomposites increased with regard to carbon nanotubes incorporated into the resin blend. In addition, at each given loading rate, nanocomposites containing MWCNT–NH 2 possessed larger loss and storage modulus values as well as higher glass transition temperatures ( T g) as compared to those with MWCNTs. These findings were attributed to evidences for contribution of amine functional groups to chemical interactions at the interface between CNTs and the resin blend matrix. Transmission electron microscopy (TEM) studies performed on the cured resin samples approved that the dispersion state of carbon nanotubes with and without amine functional groups within the matrix resin blend was adequate. This implies that 3-roll milling process described herein is very appropriate technique for blending of carbon nanotubes with a liquid thermoset resin to manufacture nanocomposites with enhanced final properties.

An enrichment method of molybdenum on a cellulose nitrate resin for the determination by electrothermal atomic absorption spectrometry coupled with the resin suspension injection.

Cellulose derivative resin (CDR) suspensions containing resin particles of cellulose nitrate (CDR(CN)), cellulose acetate (CDR(CA)), or cellulose triacetate (CDR(CTA)) were prepared as the sorbent for resin suspension injection (RSI) electrothermal atomic absorption spectrometry (ETAAS), in which fine resin particles holding a desired trace element were directly injected into the graphite tube as the suspension. To compare the sorption ability, the distribution ratios of the Mo(VI)-phenylfluorone complex were measured between the aqueous phase and the sorbents, including the CDRs mentioned above and the finely divided anion exchange resin (AR). The results showed that the sorption ability decreases in the following order: CDR(CN) > or = AR > CDR(CA) > or = CDR(CTA). It was concluded that CDR(CN) was able to extract more than 98% of Mo(VI), and was suitable for RSI-ETAAS as well as AR. CDR(CN) was used for the determination of Mo in NIES certified reference materials, No. 10 Rice flour-unpolished; the results showed fairly good agreements between the analytical values and the certified values.