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Katarina Dimic-Misic, Kari Vanhatalo, Olli Dahl, Patrick Gane
Rheological properties comparison of aqueous dispersed nanocellulose derived from a novel pathway-produced microcrystalline cellulose or by conventional methods
Appl. Rheol. 28:6 (2018) 64474 (15 pages) ►
Novel-produced never-dried and dried microcrystalline cellulose (MCC) was previously compared with a commercial MCC. The novel MCC was shown to be a suitable starting material for producing cellulose nanofibrils, in turn having similar molecular weight Mw, crystallinity, and particle size comparable to those from sequentially enzymatic and mechanically treated softwood sulphite pulp, but at lower cost. The study here presents a rheological parameterisation of the aqueous suspension throughout the process, aimed at delivering a correlation between specific surface area, at equal material particle size, and adsorptive coupling between neighbouring cellulose particles and interstitial water under flow. We conclude that combining dynamic viscosity with an independent measure of particle size provides a suitable quality control of MCC-derived cellulose nanofibrils, obviating the need for individual property-raw material relationships to be evaluated, and this principle may provide a generalised method for use in the production of cellulose nanofibrils.► Cite this publication as follows:
Dimic-Misic K, Vanhatalo K, Dahl O, Gane P: Rheological properties comparison of aqueous dispersed nanocellulose derived from a novel pathway-produced microcrystalline cellulose or by conventional methods, Appl. Rheol. 28 (2018) 64474.
Jan Ullsperger, Robert Valek
Properties of polymer solutions intended for formation of hollow fibers membranes by inversion phases process
Appl. Rheol. 28:6 (2018) 65935 (7 pages) ►
The gas separation process by asymmetric polymeric membranes has received much attention during the last decades because of its more energy efficiency than other conventional separation processes. Hollow fibers are the most favored membrane geometry owing to their high surface area per unit volume of membrane module. One of the key elements determining the potential and applications of asymmetric hollow-fiber membranes are the structural properties mainly including pore size, pore distribution, selective layer thickness, molecular orientation and defectiveness. These elements can generally vary depending on conditions during dry-jet wet-spinning process. Flow conditions in spinneret during extrusion are known to affect the dense-layer of hollow fibers and possibly to enhance separation performance of hollow fibers. The aim of this study was to determine flow conditions of polyetherimide/N-Methyl-2-pyrrolidone solvent/ethanol non-solvent spinning solutions flowing through concentric annulus of spinneret during hollow fiber spinning process. The rotational rheometer was used to characterize rheological properties of spinning solutions. Newtonian behavior of the spinning solutions with arbitrary composition was shown. The effect of spinning solution and spinneret dimension on flow profile in spinneret was investigated. The Newtonian character of the spinning solutions caused constant velocity profile resp. shear rate profile regardless of dope composition when flowing through a spinneret with some flowrate. It has been shown the spinneret dimensions and geometry play a crucial role in controlling the shear flow in spinneret. The phase behavior of the PEI/NMP/EtOH dope system at a temperature of the hollow fiber spinning process (40oC) was studied.► Cite this publication as follows:
Ullsperger J, Valek R: Properties of polymer solutions intended for formation of hollow fibers membranes by inversion phases process, Appl. Rheol. 28 (2018) 65935.
Hui Li, Yingshe Luo, Donglan Hu
Long term creep assessment of room-temperature cured epoxy adhesive by time-stress superposition and fractional rheological model
Appl. Rheol. 28:6 (2018) 64796 (10 pages) ►
The creep behavior of a new type epoxy resin adhesive which is room-temperature cured and used for reinforcing engineering structures was studied. The tensile strength of the adhesive has reached the desired values for the structural adhesive used for bonding concrete as the base material with steel. The short-term creep tests were conducted under four different stress levels. The generalized curve for reference stress was obtained by utilizing the time-stress equivalent principle. Moreover, compared with traditional Burgers model, an improved fractional KBurgers model obtained by replacing the Newton derivative with the fractional derivative element (Abel component) in the traditional Burgers model can capture the creep behavior of this epoxy adhesive with high precision in the condition of the room-temperature and tensile stress of 36 MPa.► Cite this publication as follows:
Li H, Luo Y, Hu D: Long term creep assessment of room-temperature cured epoxy adhesive by time-stress superposition and fractional rheological model, Appl. Rheol. 28 (2018) 64796.
Premanarayani Menon, Yin Yin Teo, Misni Misran
Effect of diethylaminoethyl-dextran coated liposomes on the rheological properties of carbopol gel
Appl. Rheol. 28:6 (2018) 62616 (6 pages) ►
Liposomal gel has played an important role in administration of drugs via topical and transdermal routes. Incorporation of liposome into gel not only has overcome the liquid nature of liposomal dispersion but also helped to preserve the original structure of liposome. In this study, we formulated a liposomal gel consisting of Carbopol gel and a diethylaminoethyl dextran (DEAE-DX) coated liposome. The effect of coated and non-coated liposomes on the rheological properties of Carbopol gel was investigated. The rheological results indicated that incorporation of liposomes into Carbopol gel modified the viscoelastic and flow behaviour of the gel significantly. Apart from that, liposomal gel consisting of DEAE-DX coated liposomes exhibited more solid-like behavior compared to the non-coated liposomal gel. Incorporation of DEAE-DX coated liposomes increased the yield stress of liposomal gel compared to non-coated liposomes. This supports the findings obtained from the amplitude and frequency tests whereby addition of DEAE-DX enhanced the rigidity of the gel so that the resultant gel was more resistant to flow.► Cite this publication as follows:
Menon P, Teo YY, Misran M: Effect of diethylaminoethyl-dextran coated liposomes on the rheological properties of carbopol gel, Appl. Rheol. 28 (2018) 62616.
Victor Chike Agbakoba, Percy Hlangothi, Clarence Yah, Geoffrey Simate
A study of the flow behavior of prevulcanised natural rubber latex/singlewalled carbon nanotubes (SWCNT) blends using rotational viscometry and power law model
Appl. Rheol. 28:6 (2018) 64175 (10 pages) ►
This work describes the flow behavior of prevulcanised natural rubber latex (PvNRL) and PvNRL nanoblends containing 0.02, 0.04, 0.06, and 0.08 wt.% of aqueous dispersion of single-walled carbon nanotubes (SWCNT). The assay was performed under varying shear rates (between 0.1-100 1/s) at three separate isothermal temperatures (25, 30, and 35 °C) on a Modular Compact Rheometer (MCR) fitted with a concentric cylinder measuring system. A steady decrease in viscosity upon every single shear rate increment was observed for all the samples analysed. Thus, each measured viscosity was considered an apparent-viscosity; which confirms a typical non-Newtonian flow behavior. PvNRL blends containing highest wt.% SWCNT exhibited higher apparent viscosity at low shear rates, whereas the lowest wt.% SWCNT displayed a lower apparent viscosity, thus signifying a dilution effect. The power law model showed good fitting and successfully predicted the flow behavior within the modelled shear rate region.► Cite this publication as follows:
Agbakoba VC, Hlangothi P, Yah C, Simate G: A study of the flow behavior of prevulcanised natural rubber latex/singlewalled carbon nanotubes (SWCNT) blends using rotational viscometry and power law model, Appl. Rheol. 28 (2018) 64175.
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