Controlled Shear Conditions Research Articles

Water vapor and air barrier performance of sustainable paper coatings based on PLA and xanthan gum

New stable water-based polylactic acid (PLA) emulsions with high water content were successfully prepared using two food-grade surfactants combined with high-shear mechanical mixing and ultrasonic treatment. PLA particle size distribution (PSD) was varied from micrometric to nanometric depending on the preparation conditions, as confirmed by digital microscopies and dynamic light scattering (DLS) analysis. The charged state of the PLA particle surface was evaluated using ζ-potential measurements as a significant factor affecting the stability of PLA emulsions. An unstable PLA emulsion with a large particle size has a low negative charge distribution on the surface (−26 mV) compared to the stable emulsion with a high negative charge (−39 mV). This repulsion force was sufficient to prevent flocculation and subsequent aggregation. Thickened PLA emulsions with different amounts of xanthan gum (XG) display a shear-thinning behavior in the investigated concentrations up to 2 wt% under controlled shear conditions, with apparent viscosity values dependent on XG concentrations. PLA's minimal film formation temperature (MFFT) was determined by applying a linear temperature gradient from 23 °C to 120 °C. The drying above the Tg of PLA (58 °C) resulted in clear and continuous films. Finally, the barrier properties of PLA-coated paper revealed that increasing the thickness of the PLA coating enhanced the barrier properties of the base paper considerably. The results of air and water vapor permeability tests revealed that our PLA coating in weights ranging from 10 to 15 g/m2 is suitable for achieving superior overall barrier properties combined with smooth surfaces, which are extremely important for fabricating coated paper products in the paper industry.

Densifying Co-Precipitated Amorphous Dispersions to Achieve Improved Bulk Powder Properties.

Precipitation of amorphous solid dispersions has gained traction in the pharmaceutical industry given its application to pharmaceuticals with varying physicochemical properties. Although preparing co-precipitated amorphous dispersions (cPAD) in high-shear rotor-stator devices allows for controlled shear conditions during precipitation, such aggressive mixing environments can result in materials with low bulk density and poor flowability. This work investigated annealing cPAD after precipitation by washing with heated anti-solvent to improve bulk powder properties required for downstream drug product processing. Co-precipitation dispersions were prepared by precipitation into pH-modified aqueous anti-solvent. Amorphous dispersions were washed with heated anti-solvent and assessed for bulk density, flowability, and dissolution behavior relative to both cPAD produced without a heated wash and spray dried intermediate. Washing cPAD with a heated anti-solvent resulted in an improvement in flowability and increased bulk density. The mechanism of densification was ascribed to annealing over the wetted Tg of the material, which lead to collapse of the porous co-precipitate structure into densified granules without causing crystallization. In contrast, an alternative approach to increase bulk density by precipitating the ASD using low shear conditions showed evidence of crystallinity. The dissolution rate of the densified cPAD granules was lower than that of the low-bulk density dispersions, although both samples reached concentrations equivalent to that of the spray dried intermediate after 90min dissolution. Hot wash densification was a tenable route to produce co-precipitated amorphous dispersions with improved properties for downstream processing compared to non-densified powders.

A quasi-Monte Carlo based flocculation model for fine-grained cohesive sediments in aquatic environments

The quasi-Monte Carlo (QMC) method was enhanced to solve the population balance model (PBM) including aggregation and fragmentation processes for simulating the temporal evolutions of characteristic sizes and floc size distributions (FSDs) of cohesive sediments. Ideal cases with analytical solutions were firstly adopted to validate this QMC model to illustrate selected pure aggregation, pure fragmentation, and combined aggregation and fragmentation systems. Two available laboratory data sets, one with suspended kaolinite and the other with a mixture of kaolinite and montmorillonite, were further used to monitor the FSDs of cohesive sediments in controlled shear conditions. The model results show reasonable agreements with both analytical solutions and laboratory experiments. Moreover, different QMC schemes were tested and compared with the standard Monte Carlo scheme and a Latin Hypercube Sampling scheme to optimize the model performance. It shows that all QMC schemes perform better in both accuracy and time consumption than standard Monte Carlo scheme. In particular, compared with other schemes, the QMC scheme using Halton sequence requires the least particle numbers in the simulated system to reach reasonable accuracy. In the sensitivity tests, we also show that the fractal dimension and the fragmentation distribution function have large impacts on the predicted FSDs. This study indicates a great advance in employing QMC schemes to solve PBM for simulating the flocculation of cohesive sediments.

Stasis Promotes Erythrocyte Adhesion to von Willebrand Factor.

Venous thromboembolism is a major contributor to global disease burden. Leukocytes and platelets initiate thrombogenesis on blood stasis and initiate the formation of a fibrin, VWF (von Willebrand factor), and neutrophil extracellular trap scaffold for erythrocytes. However, there is little knowledge on how erythrocytes become stably incorporated into this scaffold. Recently, we described the adhesion of calcium-loaded erythrocytes to endothelial-derived VWF strings. Because VWF is part of the scaffold of venous thrombi, we questioned whether reduced flow or stasis promotes the adhesion of normal erythrocytes to VWF and whether venous thrombi show evidence of erythrocyte-VWF interactions. In the present work, we perfused, under controlled shear conditions, washed, normal erythrocytes over surface-immobilized plasma and extracellular matrix proteins and showed that normal erythrocytes specifically bind to VWF. The interaction between erythrocytes and VWF significantly increased when the wall shear stress was reduced. Next, we investigated whether erythrocyte-VWF interactions support the structure of venous thrombi. High-resolution immunofluorescence imaging of human venous thrombi showed a striking pattern between erythrocytes, VWF, and fibrin, which suggests that VWF plays a supporting role, linking erythrocytes to fibrin in the thrombus. Our data suggest that erythrocyte retention in venous thrombi is mediated by erythrocyte-VWF or erythrocyte-VWF-fibrin interactions. Targeting erythrocyte retention could be a new strategy in the treatment or prevention of venous thrombosis.

Large-Scale Production of Nanographite by Tube-Shear Exfoliation in Water.

The number of applications based on graphene, few-layer graphene, and nanographite is rapidly increasing. A large-scale process for production of these materials is critically needed to achieve cost-effective commercial products. Here, we present a novel process to mechanically exfoliate industrial quantities of nanographite from graphite in an aqueous environment with low energy consumption and at controlled shear conditions. This process, based on hydrodynamic tube shearing, produced nanometer-thick and micrometer-wide flakes of nanographite with a production rate exceeding 500 gh-1 with an energy consumption about 10 Whg-1. In addition, to facilitate large-area coating, we show that the nanographite can be mixed with nanofibrillated cellulose in the process to form highly conductive, robust and environmentally friendly composites. This composite has a sheet resistance below 1.75 Ω/sq and an electrical resistivity of 1.39×10-4 Ωm and may find use in several applications, from supercapacitors and batteries to printed electronics and solar cells. A batch of 100 liter was processed in less than 4 hours. The design of the process allow scaling to even larger volumes and the low energy consumption indicates a low-cost process.

Studying solutions at high shear rates: a dedicated microfluidics setup

The development of a dedicated small-angle X-ray scattering setup for the investigation of complex fluids at different controlled shear conditions is reported. The setup utilizes a microfluidics chip with a narrowing channel. As a consequence, a shear gradient is generated within the channel and the effect of shear rate on structure and interactions is mapped spatially. In a first experiment small-angle X-ray scattering is utilized to investigate highly concentrated protein solutions up to a shear rate of 300000 s(-1). These data demonstrate that equilibrium clusters of lysozyme are destabilized at high shear rates.

Production of liposomes using microengineered membrane and co-flow microfluidic device

Two modified ethanol injection methods have been used to produce Lipoid® E80 and POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) liposomes: (i) injection of the organic phase through a microengineered nickel membrane kept under controlled shear conditions and (ii) injection of the organic phase through a tapered-end glass capillary into co-flowing aqueous stream using coaxial assemblies of glass capillaries. The organic phase was composed of 20mgml−1 of phospholipids and 5mgml−1 of cholesterol dissolved in ethanol and the aqueous phase was ultra-pure water. Self-assembly of phospholipid molecules into multiple concentric bilayers via phospolipid bilayered fragments was initiated by interpenetration of the two miscible solvents. The mean vesicle size in the membrane method was 80±3nm and consistent across all of the devices (stirred cell, cross-flow module and oscillating membrane system), indicating that local or temporal variations of the shear stress on the membrane surface had no effect on the vesicle size, on the condition that a maximum shear stress was kept constant. The mean vesicle size in co-flow microfludic device decreased from 131 to 73nm when the orifice diameter in the injection capillary was reduced from 209 to 42μm at the aqueous and organic phase flow rate of 25 and 5.55mlh−1, respectively. The vesicle size was significantly affected by the mixing efficiency, which was controlled by the orifice size and liquid flow rates. The smallest vesicle size was obtained under conditions that promote the highest mixing rate. Computational Fluid Dynamics (CFD) simulations were performed to study the mixing process in the vicinity of the orifice.

Distribution of fat droplets/particles and protein film components in batters of lean and back fat produced under controlled shear conditions

Meat batters were made with lean pork and back fat in a vacuum bowl chopper. The integrated light scattering analysis showed that the droplet/particle size distribution in the batters was bimodal for 3, 5, and 7 min of chopping. The distance between the two peaks in a distribution curve was gradually reduced with shearing time. Back fat was sheared into various sizes and shapes of droplets/particles in meat batters. The results showed that regardless of raw meat batter or meat-batter gel, fat globules, particles, and clusters were all surrounded with smooth protein films and entrapped in a rigid protein matrix. The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that the protein films consisted of C-protein, actin, α-actinin, troponin T, tropomyosin, and other proteins besides myosin. The results could help us to better understand the emulsion mechanism for meat batters.

Breakage and re-growth of flocs: Effect of additional doses of coagulant species

Several polyaluminum chloride (PACl) coagulants were prepared, with different OH/Al ratios (B values), and characterized by Ferron assay. These were used in studies of floc formation, breakage and re-growth with kaolin suspensions under controlled shear conditions, using a continuous optical monitoring method. Particular attention was paid to the effect of small additional coagulant dosages, added during the floc breakage period, on the re-growth of broken flocs. The results showed that the re-growth ability was greatly dependent on the nature of the PACl species added as second coagulant. The re-growth ability of broken flocs was greatest when the second coagulant was PACl 0 (i.e. AlCl 3, with B = 0) and least with PACl 25 ( B = 2.5). In the latter case there was no effect on floc re-growth, irrespective of the initial coagulant used. PACls with intermediate B values gave some improvement in floc re-growth, but less than that with PACl 0. Additional dosage of PACl 0 gave re-grown flocs about the same size or even larger than those before breakage. The re-growth of broken flocs is significantly correlated with the species Al a (monomeric) and Al b (polymeric), as determined by Ferron assay. The amorphous hydroxide precipitate formed from PACl 0, (mainly Al a) can greatly improve the adhesion between broken flocs and give complete re-growth. However, for PACl 25, mostly composed of Al b, the nature of the precipitate is different and there is no effect on floc re-growth.

Integrated system investigating shear-mediated platelet interactions with von Willebrand factor using microliters of whole blood

We report an integrated platelet translocation analysis system that measures complex dynamic platelet–protein surface interactions in microliter volumes of unmodified anticoagulated whole blood under controlled fluid shear conditions. The integrated system combines customized platelet-tracking image analysis with a custom-designed microfluidic parallel plate flow chamber and defined von Willebrand factor surfaces to assess platelet trajectories. Using a position-based probability function that accounts for image noise and preference for downstream movement, outputs include instantaneous and mean platelet velocities, periods of motion and stasis, and bond dissociation kinetics. Whole blood flow data from healthy donors at an arterial shear rate (1500 s −1) show mean platelet velocities from 8.9 ± 1.0 to 12 ± 4 μm s −1. Platelets in blood treated with the antiplatelet agent c7E-Fab fragment spend more than twice as much time in motion as platelets from untreated control blood; the bond dissociation rate constant ( k off) increases 1.3-fold, whereas mean translocation velocities do not differ. Blood from healthy unmedicated donors was used to assess flow assay reproducibility, donor variability, and the effects of antiplatelet treatment. This integrated system enables reliable, rapid populational quantification of platelet translocation under pathophysiological vascular fluid shear using as little as 150 μl of blood.

The effect of shear on gravity thickening: Pilot scale modelling

Mathematical models are potentially a valuable tool for the prediction of continuous gravity thickener operation. However, experience shows that existing mathematical models underestimate dewatering in thickeners for flocculated feed materials when predictions are made of either the underflow solids concentration for a given solids feed flux density or the maximum solids feed flux density achievable for a minimum underflow solids concentration set point. One reason postulated for this discrepancy is shear enhancement of sedimentation and bed dewatering as a result of aggregate densification. This process is not taken into account in conventional 1-D thickener models. A pilot scale column, operated at low bed heights without the addition of mechanical shear, produced results that compared well with 1-D model predictions. The effect of mechanical shear and/or greater bed height was to significantly enhance thickener performance relative to model predictions (as measured by underflow density or maximum solids flux density achievable for a nominated underflow density). An experimental method was developed that enabled shear to be incorporated into the suspension dewatering characterisation. The results suggest an order of magnitude increase in solid flux density can be expected under controlled shear conditions with polymer flocculated aggregates. The results also indicate that mechanical shear is not the only factor that can enhance dewatering, since higher beds, and hence longer residence times, also improve the achievable solids flux density. This is despite the fact that the thickener is operating in a regime that is predicted to be limited by the sediment permeability and not its compressibility. This suggests an additional mechanism must be at play in full scale operation and points a direction for further experimentation.

Microbial community structure in activated sludge floc analysed by fluorescence in situ hybridization and its relation to floc stability

The efficiency of activated sludge treatment plants is dependent on the solid–liquid separation properties of the activated sludge. A critical parameter is the stability of the microbial flocs. Weak flocs deflocculate easily leaving increased concentrations of suspended solids in the effluent. The knowledge about how different bacteria are attached to the flocs and their influence on the bioflocculation is limited. In this study, the deflocculation of different phylogenetic groups of bacteria in activated sludge from a full scale plant was investigated. The experiments were carried out by using a shear method where the sludge flocs are deflocculated under controlled shear conditions. The degree of deflocculation was measured as increase in turbidity of the supernatant. Identification and quantification of the microbial community structure of both total activated sludge and deflocculated bacteria were conducted with group-specific gene probes for broad groups of bacteria ( Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria and Actinobacteria) and fluorescence in situ hybridization (FISH). The microbial community structure of the deflocculated bacteria was different compared to the total activated sludge with a higher abundance of Gammaproteobacteria in the supernatant indicating that different groups of bacteria are bound with different strength to the floc surface. The results show that the bacteria in the outer parts of the flocs are relatively loosely bound to the floc matrix and can be easily eroded from the surface when exposed to shear.

Evaluation of Children with Suspected Bleeding Disorder Applying the Impact-R [Cone and Plate(let) Analyzer

Background: von Willebrand's disease (VWD) is the most common bleeding disorder, affecting between 1–10% of the general population. There is a need for a simple test to screen patients with bleeding symptoms before more labor-intensive diagnostic steps are taken. The Impact-R [Cone and Plate(let) Analyzer (CPA)] (DiaMed Switzerland), was designed in an attempt to test platelet function under close to physiological conditions. Citrated whole blood is applied on polystyrene surface, under controlled shear conditions using a cone and plate device, followed by a quantitative analysis of platelet deposition to immobilized plasma von Willebrand's factor (VWF) and fibrinogen. Results of the test are presented for adhesion as % surface coverage (SC) and for aggregation as average size (μm2, AS). In this study we report the use of CPA test in evaluation of children with suspected bleeding disorder.Methods: Fifty-four consecutive children with bleeding symptoms and normal platelet count and coagulation tests were evaluated between August 1st, 2006 and July 31, 2007. In addition to the CPA test, all children were tested for VWF: antigen plasma level, VWF: ristocetin activity, factor VIII: C plasma level, platelet aggregation test using turbidometric aggregometer (Helena, USA) and blood type. The study was approved by the local Helsinki committee. Statistical analysis was done by SPSS.Results: Of 54 children, 10 (18.9%) were diagnosed with VWD and 6 (11.1%) children were diagnosed with platelet function defect according to bleeding history, family history, aggregation and factor VIII/VWF tests. To test the validity of the CPA as a screening test for diagnosis of VWD and platelet function defects a ROC curve was formulated for both SC and AS measurements. The best cutting point for a positive test was equal or less then 6.5% for SC measurement (sensitivity 60%, specificity 65%), and equal or lest then 26.5μm2 for AS measurement (sensitivity 67%, specificity 81.6%). The predictive value of a normal CPA test (negative predictive value), i.e. SC > 6.5% and AS > 26.5μm2, was 92%. Of the 26 normal CPA tests, one child was diagnosed with mild type I VWD and one child was diagnosed with mild platelet defect in response to epinephrine (40%). The predictive value of an abnormal CPA test (positive predictive value) was 50%. Of the 28 abnormal CPA test, 9 children were diagnosed with VWD, 4 children with platelet defect in response to epinephrine (<30%) and one child with platelet defect in response to collagen (10%). Significant bleeding symptoms (bleeding score 3 or more) were reported in 4 of 14 children with abnormal CPA test but with normal VWF, normal factor VIII and normal platelet aggregation.Conclusions: The CPA test was found to be a useful tool for excluding VWD and platelet function defect in children suspected for bleeding disorder. Yet, in case of an abnormal CPA test, further testing are needed. Interestingly, abnormal CPA test was the only finding in some children with a significant bleeding history, suggesting other underlying adhesion defects yet to be described.

Degradation of supercoiled plasmid DNA within a capillary device

Supercoiled plasmid DNA is susceptible to fluid stress in large-scale manufacturing processes. A capillary device was used to generate controlled shear conditions and the effects of different stresses on plasmid DNA structure were investigated. Computational fluid dynamics (CFD) analysis was employed to characterize the flow environment in the capillary device and different analytical techniques were used to quantify the DNA breakage. It was found that the degradation of plasmid DNA occurred at the entrance of the capillary and that the shear stress within the capillary did not affect the DNA structure. The degradation rate of plasmids was well correlated with the average elongational strain rate or the pressure drop at the entrance region. The conclusion may also be drawn that laminar shear stress does not play a significant role in plasmid DNA degradation.

Apparatus for Emulsion Production in Small Scale and Under Controlled Shear Conditions

In this article, a rotor–stator apparatus for the production of 5 g batches of emulsion is introduced. Special attention was paid to the design of the apparatus and its construction, ensuring close tolerances in all machined parts. The size of the dispersing gap was 500 mm. The need to prepare small quantities of homogeneous emulsion formulations containing costly ingredients formed the impetus for this work. We present a set of emulsion production experiments using a model mayonnaise recipe with a weight percentage of dispersed oil of 80%, and illustrate the effect of rotor speed on the average size and size distributions of the resulting oil droplets. These size distributions were within the same range as a commercial mayonnaise. The maximum shear rates and corresponding shear stresses existing in the apparatus at different rotational speeds were estimated. A stabilization time related to rotor speed and geometry was also calculated. We discuss the scale-up of emulsion production, giving consideration to the length of time the shear stress is applied as well as to the magnitude of the shear stress.

Key Factors in Membrane Emulsification

In contrast to widely used emulsification processes (high pressure homogenizers, rotor/ stator, etc.), emulsions can be made with mineral membranes in relatively low and controlled shear conditions. In this system, the dispersed phase permeates through membrane pores into the continuous phase circulating in the retentate loop. Droplets detach from the membrane owing to the shearing of the continuous phase. This process produces only a little heating, energy consumption is low. This is interesting both from economic and technological points of view, because it may limit the denaturation of macromolecular emulsifiers. The influence of some factors (membranes, working conditions, emulsifiers) on the droplet size of oil-water emulsions was studied. The sizes depended mainly on the adsorption speed of emulsifiers: emulsions were much finer with emulsifiers adsorbing quickly at the interface, such as SDS (sodium dodecyl sulfate) than with emulsifiers lowering the interfacial tension more slowly, such as β-casein or 11S soya globulin. The membrane pore size, the shear rate at the membrane surface and, to a lesser extent, the volume fraction of the oil phase (between 0 and 30%) had also a significant effect, unlike the oil flux. The emulsions were finer and more stable than those obtained in the same conditions with a rotor/stator system.

A constitutive relation describing the shear-banding transition.

An additional contribution to the standard expression for the shear stress must be considered in order to describe shear banding. A possible extension of the standard constitutive relation is proposed. Its physical, purely hydrodynamic origin is discussed. The corresponding Navier-Stokes equation is analyzed for the two-plate geometry, where flow gradients are assumed to exist only in the direction perpendicular to the two plates. The linearized Navier-Stokes equation is shown to be very similar to the Cahn-Hilliard equation for spinodal decomposition, with a similar term that stabilizes rapid spatial variations. Only slowly varying flow gradients are unstable. Just as in the initial stage of spinodal decomposition there is a most rapidly growing wavelength in the initial stage of the shear-banding transition, leading to a predictable number of shear bands. A modified Maxwell equal area construction is derived, which dictates the stress and the shear rates in the bands under controlled shear conditions, and which shows that under controlled stress conditions no true shear bands can coexist. The kinetics of the shear-banding transition is studied numerically. For the two-plate geometry it is found that there exist multiple stationary states under controlled shear conditions, depending on the initial state of the flow profile. Shear banding occurs not only when the system is initially unstable, but can also be induced outside the unstable region when the amplitude of the initial perturbation is large enough. The shear-banding transition can thus proceed via "spinodal demixing" (from an unstable initial state) or via "condensation." Under controlled stress conditions no stationary state is found. Here, coupling with flow gradients extending in other directions, not perpendicular to the two plates, should probably be taken into account.

Characterization of nanocrystalline Fe–45 at% Al intermetallic powders obtained by controlled ball milling and the influence of annealing

An ingot of the binary Fe–45 at% Al intermetallic with ordered B2 crystallographic structure was machined into chips and ball milled under controlled shear conditions to produce powders with a nanocrystalline grain size. Some milled powders were additionally annealed at 600°C. The average powder particle size decreased with milling time attaining 8±8 μm after 210 h of milling. Milled powders became strongly ferromagnetic. The B2 superlattice reflections in X-ray diffraction (XRD) were undetectable even after the shortest milling time of 23 h, indicating a complete disorder. Formation of nanocrystallites was confirmed by the XRD peak broadening and the XRD estimated nanocrystallite size decreased from 40 nm after 23 h to the 12–7 nm range after 47 to 210 h of milling. Lattice constant of powders increased during the first 23 h of milling, remaining approximately constant for longer milling times. This change is attributed to the formation of antisite-atom pairs. An attempt has been made to correlate the microhardness of milled powders (disordered BCC solid solution) with their nanocrystalline grain size through the Hall-Petch (H-P) relationship: HV0.01=603.6+279.8d −0.5 kg mm −2 where HV0.01 is Vickers microhardness at 0.01 kg and d is nanocrystalline grain size in nm. The data fit was very poor ( R 2=0.49 only). The relationship is very weak as indicated by a small value of the H–P slope. The “inverse” H–P relationship for the finest nanocrystallites cannot be entirely ruled out. After annealing at 600°C the relative long range order (LRO) parameter, S, was not fully restored to ∼1.0 but attained a value ∼0.8–0.9 while both microhardness and lattice constant were slightly higher than those of the homogenized B2 Fe–45Al intermetallic. These changes are attributed to the existence of some “residual” antisite–atom pairs retained after annealing. DTA studies of milled powders show two exothermic peaks with their maxima at 190 and 850°C. The low-temperature peak is attributed to the ferromagnetic to paramagnetic transition and a simultaneous disorder/order transformation. The high-temperature one is probably related to the recrystallization and/or nanocrystallite grain growth.

Morphological development with time for immiscible polymer blends with an in situ compatibilizer under controlled shear conditions

We have studied morphological development with time under controlled shear condition for 75/25 wt/wt poly(butylene terephthalate) (PBT) and polystyrene (PS) blend having various amounts of poly(styrene- ran-glycidyl methacrylate) (PS-GMA) as an in situ compatibilizer prepared by solution blending method. The morphology of the blend without PS-GMA develops via a coarsening process during an annealing at higher temperatures. However, the dispersed domain size of the blend with PS-GMA increases slowly at an early stage of annealing, and then levels off. This is due to the in situ formation of graft copolymers at the interface. As the initial amount of PS-GMA in the blend increases, enough of the copolymers for the dispersed domain size in the blend to be levelled off are formed at shorter times. An oscillatory shearing with the frequency range 0.5–10 rad s −1 can induce the coalescence of the dispersed domain in the blend without PS-GMA. However, for the blend with PS-GMA the shear-induced coalescence of the dispersed domain is successfully suppressed by the graft copolymers formed in situ at the interface. The time evolutions of shear storage modulus ( G′) and complex viscosity ( η*) for blends with PS-GMA are strongly affected by the blend morphology which in turn depends on the initial amount of PS-GMA in the blend.

Crystallization of sheared polymer melts: poly(ethylene oxide) fractions

Crystallization under controlled shear conditions has been optically monitored for a series of sharp molecular weight fractions of poly(ethylene oxide). The minimum shear rate (MSR) necessary to produce oriented crystalline morphologies exhibited a strong molecular weight (M) dependence: MSR=K/M1.47. The time necessary for erasure of orientation effects after crystal melting was also determined and found to be proportional to M1.42.