During the processing of elastomeric compounds under high flow rates, significant pressure drops (106–108 Pa) are encountered. Under such conditions, the viscosity of these compounds is significantly affected by pressure and viscous heating. Moreover, strong flow rates may cause these systems to slip at the wall, violating the classical no-slip boundary condition of fluid mechanics. To determine the slip velocity by the well-known Mooney method, the effects of pressure and viscous heating should be considered. In this work, an experimental methodology is developed to determine the slip velocity of styrene–butadiene compounds in capillary flow corrected for the effects of pressure and viscous heating. First, the temperature increase due to viscous heating is measured during the extrusion process and accounted for in correcting the experimental data to infer the slip velocity. Consequently, the corrected experimental data for the effects of pressure and viscous heating are used to calculate the slip velocity from the deviation of the linear viscoelastic behavior (deviation from the Cox–Merz rule). The Mooney method is also used to confirm the calculated slip velocity of the elastomeric compounds.

LebensmittelchemieVolume 77, Issue S1 p. S1-148-S1-148 Aritlce HPLC-80 MHz 1H NMR method development on parabens Markus Matz, Markus Matz Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Engesserstr. 18, 76131 Karlsruhe, GermanySearch for more papers by this authorCarlo Botha, Carlo Botha Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Engesserstr. 18, 76131 Karlsruhe, GermanySearch for more papers by this authorMichael Pollard, Michael Pollard Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Engesserstr. 18, 76131 Karlsruhe, GermanySearch for more papers by this authorMarianne Gaborieau, Marianne Gaborieau Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Engesserstr. 18, 76131 Karlsruhe, GermanySearch for more papers by this authorManfred Wilhelm, Manfred Wilhelm Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Engesserstr. 18, 76131 Karlsruhe, GermanySearch for more papers by this author Markus Matz, Markus Matz Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Engesserstr. 18, 76131 Karlsruhe, GermanySearch for more papers by this authorCarlo Botha, Carlo Botha Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Engesserstr. 18, 76131 Karlsruhe, GermanySearch for more papers by this authorMichael Pollard, Michael Pollard Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Engesserstr. 18, 76131 Karlsruhe, GermanySearch for more papers by this authorMarianne Gaborieau, Marianne Gaborieau Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Engesserstr. 18, 76131 Karlsruhe, GermanySearch for more papers by this authorManfred Wilhelm, Manfred Wilhelm Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology, Engesserstr. 18, 76131 Karlsruhe, GermanySearch for more papers by this author First published: 01 March 2023 https://doi.org/10.1002/lemi.202352118AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume77, IssueS1Supplement: Abstracts der Vorträge der Regionalverbände und die der Posterflashtalks der AG JLCMarch 2023Pages S1-148-S1-148 RelatedInformation

The extrusion flow instabilities of commercial polybutadiene (PBD) are investigated as a function of the different extrusion die geometries, such as round capillary, slit, and complex cross-section profile slit dies via capillary rheology. Qualitative models are used to fit the experimental data for the spatial characteristic wavelength (lambda) of the appearing extrusion flow instabilities. A new qualitative model for the slit die geometry, rectangular cross-section, is derived based on the theoretical concept of the "two layers" extrudate and the force balance at the die exit region. The proposed qualitative model for the slit die geometry is used to predict the spatial characteristic wavelength (lambda) for extrudates obtained by complex cross-section profile slit die geometries similar to industrial manufacturing. Correlation between the ratio of the extensional (Y-s) and shear (sigma(x)) stress at the die exit area and the characteristic dimension, height H for slit dies and diameter D for round capillary dies, is presented. Moreover, a geometry-dependent model is used to predict the spatial characteristic wavelength (lambda) of the extrusion flow instabilities from a round capillary die to a slit die and vice versa.

The extrusion flow instabilities of three commercial styrene-butadiene rubbers (SBR) are investigated as a function of molecular weight distribution (MWD); molecular architecture (linear, branched); and temperature. The samples have multimodal MWD, with the main component being SBR and a low amount, less than 10 wt. %, of low-molecular weight hydrocarbons. Deviation from the Cox–Merz rule at high angular frequencies/shear rates becomes intense as the amount of medium-molecular weight component increases. Optical analysis is used to identify and quantify spatial surface distortions, specifically wavelength (λ) and height (h), of the different types of extrusion flow instabilities. Qualitative constitutive models are reviewed and used to fit the experimental data for the spatial characteristics of extrusion flow instability. The fitting parameters as obtained by the models are correlated with molecular properties of the materials. It is found that the characteristic spatial wavelength (λ) increases as the extrusion temperature decreases. Hence, the influence of temperature on the spatial characteristic wavelength is investigated and an Arrhenius behavior is observed.

Based on experimental work involving evaluation of viscosity enhancement of aqueous solutions by high molecular weight guar gum, we have observed that the shear viscosity scaling exponent b for semi-dilute solutions, ηsp ~ (c[η])(b), is sensitive to molecular weight, being approximately 4.7 for native samples and decreasing progressively as Mw is lowered. The critical overlap parameter demarcating the dilute and semi-dilute regimes also depends on the molecular weight as (c[η])* ~Mw(-0.82). Consequently, viscosity-concentration plots fail to achieve overlap using only specific viscosity and overlap concentration as reducing variables, a commonly accepted empiricism for random-coil polysaccharides. To bridge the gap, we propose to account for water solubility, its temperature dependence and the resulting chain flexibility as additional factors to fully describe the solution behavior of these highly-important raw materials.

Galactomannans isolated from legume seed endosperms, including those of commercial interest, have been characterized by multidetection aqueous SEC. Galactomannans derived from seeds of the Faboideae subfamily had substantially higher Mw than those from Caesalpinioideae seeds (Mw,Fab = 2.4–3.1 × 106 g/mol, Mw,Caes. = 0.86–2.1 × 106 g/mol) and within the latter botanical subfamily, an apparent correlation between Mw and the degree of galactose substitution DG was found. The molar mass distributions were unimodal and differed primarily by a scale factor, with distributional widths narrower than a true Flory 'most-probable distribution'; good fits to Schulz–Zimm model were obtained. Across subfamilies no differences were found in the exponents of [η]–M and Rv–M relationships (0.61 ± 0.02, 0.54 ± 0.01, respectively), the Flory chain stiffness ratio (C∞ = 20 ± 1 (BSF analysis)), or the persistence length (Lp = 5.5 ± 0.2 nm) obtained from SEC fraction data. However, it was found that prefactors in the [η]–M and Rv–M relationships as well as the unperturbed parameter KΘ decrease in proportion to DG and therefore chain density. Generalized relationships incorporating galactose-dependent prefactors were therefore developed to model SEC fraction data of native galactomannans ([η]GM = (1800 ± 200) × Mo−1.61 × M0.61±0.02, Rv,GM = 0.63 ± 0.05 × Mo−0.54 × M0.54±0.01) as well as lower-M fractions obtained by ultrasonication ([η]GM = (730 ± 100) × Mo−1.71 × Mw0.71±0.02, Rv,GM = 0.49 ± 0.05 × Mo−0.57 × Mw0.57±0.01, M ≈ 1 × 105-native). As a consequence of this dependence and the observed patterns in molar mass variation, [η] varies within a narrow range for galactomannans as a whole despite substantial Mw differences.

Galactomannan polysaccharides extracted from seed endosperms of 12 species of the genus Sesbania (legume subfamily Faboideae) have been characterized by size-exclusion chromatography, dilute-solution viscometry, and oscillatory-shear rheology to determine their potential as aqueous thickeners. The molecular composition and chain-length distribution were found to be nearly identical, and thus galactomannans within this genus are presumed to share a common molecular structure (DSgal≈0.7, Mw≈2.5×106, PDI≈2). Solutions at c>c* exhibited shear-thinning behavior, and strong dependence of viscosity on concentration (η∼c5). Purified samples had Huggins’ constants near 0.5, and negligible surface activity based on pendant drop tensiometry. Seed characteristics such as shape, mass, and endosperm content were also assessed, and based on this investigation, some Sesbania legume endosperms are advantageous for industrial processing and could be adapted for guar gum replacement.

Foods, consumer products and cosmetics belong to a wide range of colloidal and non-colloidal materials. Often, they are composite materials comprising several classes of fluid and solid constituents, including biopolymer gels, particulate suspensions, emulsions and foams. Length scales relevant for such materials may be anywhere between those associated with the molecular conformation of the ingredients up to long-scale dimensions of processing flows. The corresponding time scales may be in the sub-millisecond regime during aggregation of the ingredients or up to years during the shelf life of the final product. Rheological research of food material focuses on both the interaction between its ingredients, which might exhibit a complex rheological response function themselves and the influence of processing on the food structure and its properties. This brief overview summarizes suitable food rheology approaches and is grouped by the degree of abstraction of length scales and interactions. To cite this article: P. Fischer et al., C R. Physique 10 (2009). (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

The molecular weight distribution has been determined for the galactomannan solubilized from three types of locust bean gum (LBG) flours: single carob seeds, mixtures, and a range of commercial products. To prepare crude endosperm flours from carob seeds with minimal galactomannan degradation, a new extraction and milling method was developed. The method consists of applying a brief thermal shock to the seeds, followed by an extended 3-day swelling period, and manual separation of endosperms; particle size reduction to a flour is accomplished on hydrated endosperms using a centrifugal mill. This method was optimized so that redissolved LBG flours produced solutions with the highest possible viscosity and the least amount of galactomannan degradation as determined by SEC. For the three samples types, the molecular weight distribution, w(M), was found to be unimodal, appearing as a sharply defined main peak (Mp≈1.1×106g/mol) with a small high molecular weight tail (up to 2.0×106g/mol) and broad low molecular weight tail (down to 0.01×106g/mol); polydispersities (Mw/Mn) were estimated to be 1.5–1.8. Variations in Mw and [η] for galactomannans extracted from individual seeds originating from the same carob tree were minimal and nearly indistinguishable from a bulk mixture (6 seeds, Mw=0.96–1.1×106g/mol, [η]=14.2–15.1dl/g). There was a higher variability in these molecular parameters for galactomannans solubilized from commercial LBG flours, which generally exhibited lower Mw and [η], broader distributions, and reduced solubilities (Mw=0.86–1.0×106g/mol, [η]=12.4–13.6dl/g). These side-effects were attributed to damage caused by industrial scale seed processing. The near constancy of Mp for the three sample types suggests that the average molecular size of LBG galactomannan varies only slightly due to natural or biological causes.

The equilibrium aqueous solubility of a commercial carob flour was investigated by determining the percentage of soluble and insoluble components as a function of dissolution temperature. The cumulative polysaccharide yield was ca. 50% at 5°C, increasing approximately as a linear function of temperature to ca. 90% at 85°C. Overall molecular weight and intrinsic viscosity of the soluble polysaccharide were determined by size-exclusion chromatography. With increasing dissolution temperature, there was weak trend towards higher overall molecular weight and intrinsic viscosity: Mw from 1060 to 1150kg/mol, and [η] from 11.8 to 12.5dl/g, between 5 and 65°C, respectively. Broad, amorphous peaks were evident in the wide-angle X-ray scattering profiles, indicating no role for polysaccharide melting. The continuous increase of molecular weight and decrease of DSgal with dissolution temperature is interpreted as the result of thermodynamic partitioning based on a classical polymer-solvent fractionation, a mechanism that applies only for polysaccharide components with DSgal<0.35 within the accessible temperature range.

Galactomannans are nonionic, linear polysaccharides used as thickeners/stabilizers, co-gellants, and fat replacers in ice creams, sauces, and other food products. The primary biosynthetic product is a poly((1→4)-β-d-mannose) having degree of polymerization ∼1000, with a statistical distribution of single-unit (1→6)-α-d-galactose side groups. At low degrees of galactose substitution, these polymers are partially soluble in water and display a tendency to form mechanically weak gels in single-component solutions. Though partial solubility and gelation are linked to the concentration of galactose substituents and their substitutional pattern, a quantitative basis in terms of solvent quality and thermodynamic compatibility with other biopolymers has not been established. Here we summarize literature data relevant to the question of partial solubility in locust bean galactomannans. Based on our hypothesis that dissolution corresponds to an aqueous fractionation by composition and molecular weight, we suggest that water is a poor solvent for a significant portion of the polymeric components in this material. Further systematic studies of the solubility should offer new pathways to product enhancement by focusing on the underlying composition and molecular weight distributions.

Branch contents in sparsely short-chain branched polyethylenes ( 100 000 g/mol was shown to be feasible in both solid-state and melt measurements in less than a one-day measurement, obtained on a 500 MHz spectrometer and 4 mm rotor. Using this enhanced signal intensity, NMR relaxation times were investigated in the melt with respect to their inherent sensitivity to the branching architecture. These measurements included T-1rho, T-1, and T-1(NOE). It was found that T-1(NOE) seems to have the best sensitivity to determine the approximate length of the side chain branches for n > 6.

Linear and Fourier-transform rheology were used to study the influence of the oscillatory shear amplitude, gamma(0), on the isothermal crystallization at 140degreesC of three commercial isotactic polypropylenes. The development of the crystallization was monitored through the time dependence of the dynamic storage modulus, G'(t), and the normalized intensity of the third harmonic of the stress waveform, I-3(t), a quantification of the degree of nonlinearity under oscillatory shear conditions. A change in the exponent, n, of the power law describing growth, according to G'(,norm)(t) similar to t(n), was observed at t similar to 4 h. For t < 4 h, n was between 3 and 4. This change in growth kinetics was also accompanied by a maximum in I-3(t). Below &gamma;(0) = 0.05, these results were independent of the applied strain amplitude. Above &gamma;(0) = 0.05, failure of the polypropylene in the parallel plate geometry due to stress build-up was often observed in the late stages of crystallization. This was accompanied by a sharp decrease of G'(t), and a simultaneous sharp increase of I-3(t). Additionally, the presence of even harmonies in the spectrum was observed after failure. Notably, a plateau of I-3(t) at least 1 h before actual failure indicating a greater sensitivity to its onset than that of G'(t).

Earlier experimental investigations performed on a family of block copolymers formed from styrene and a homologous series of n-alkyl methacrylates revealed a strong dependence of thermodynamic compatibility between the two blocks on the length of the alkyl side chain of the methacrylate. Here we report the effect of hydrostatic pressure on the phase behavior of the same series of block copolymers as determined by in situ small-angle neutron scattering. We find that hydrostatic pressure is a very effective means of driving styrene/n-alkyl methacrylate block copolymers with intermediate side chains from the highly viscous ordered state to the fluid disordered state of the copolymer. Hence, for n ranging from 2 to 6 (ethyl to hexyl methacrylate), pressure induces mixing with an absolute value of the pressure coefficient of the order/disorder transition, dT(ODT)/dP, of up to 1.5degrees C/MPa (150degrees C/kbar). Similar results are obtained when the methacrylate block consists of a random sequence of short and long alkyl side chains with carefully chosen and predictable composition. In contrast, pressure suppresses mixing when the methacrylate block is composed of either very short (n = 1) or very long (n > 8) side chains. In terms of rheological properties, these results indicate that pressure applied at a constant temperature can be used to induce flow in some copolymers of this series. The ability to design such "baroplastic" behavior into commercially relevant thermoplastic elastomers would be highly advantageous from a processing standpoint.

THE DISORDER-TO-ORDER PHASE TRANSITION IN POLY(STYRENE-BLOCK-N-BUTYL METHACRYLATE): THE EFFECT OF PRESSURE SEPTEMBER 2001 MICHAEL A. POLLARD, B. S., UNIVERSITY OF SOUTHERN MISSISSIPPI M. S., UNIVERSITY OF MASSACHUSETTS AMHERST Ph. D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Thomas P. Russell The effect of hydrostatic pressure on the lower disorder-to-order transition (LDOT) in poly(d-styrene-Woc/c-n-butyl methacrylate) having symmetric and asymmetric block lengths was investigated by in situ small-angle neutron scattering (SANS). Currently, linear diblock copolymers having styrenic and methacrylic monomers are the only systems that display a thermally accessible phase transition from the disordered homogeneous melt to the ordered microphase-separated state upon heating. The location of this phase transition was mapped as a function of temperature and pressure by analyzing one-dimensional SANS intensities, where discontinuities in the width and height of the scattering peak indicated the traversal of the transition isothermally or isobarically. The T-P phase diagram of p(d-S-b-nBMA) built using this method shows an expansion of the disordered, homogenous region with increasing pressure. For the

The influence of compressed carbon dioxide sorption on the phase behavior of polymer blends and diblock copolymers exhibiting lower critical solution temperatures (LCSTs) and lower disorder-to-order transitions (LDOTs), respectively, was studied using in situ high-pressure small-angle neutron scattering. Homogeneous blends of poly(deuterated styrene) and poly(vinyl methyl ether) phase separate at temperatures more than 115 °C below the ambient pressure LCST upon sorption of less than 3.3 wt % CO 2 . The LDOTs in symmetric poly(deuterated styrene)-block-poly(n-butyl methacrylate) copolymers having total molecular weights of 78 000 and 32 000 g/mol are depressed by as much as 250 °C upon exposure to supercritical CO 2 at modest fluid-phase densities.

The lower critical ordering of diblock copolymers is an entropically driven phase transition that is accompanied by a negative volume change on mixing. Small angle: neutron scattering (SANS) studies of the phase transition under hydrostatic pressure has shown a very large pressure coefficient delta T/delta P = 147 degrees C/ kbar. Differential scanning calorimetry studies of the phase transition show that the transition from the disordered to the ordered state is endothermic: with an enthalpy, Delta H similar to 0.2 J/g. X-ray reflectivity studies of thin copolymer films as a function of temperature exhibits the characteristic thermal expansion of the copolymer film with a discrete change in the film thickness at the transition that corresponds to a 0.35 % volume change. This agrees, within the same order of magnitude, with what would be predicted from the Clapeyron equation.