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Rheological
Terms modified by Rheological Selected AbstractsRHEOLOGICAL AND SENSORY QUALITY OF READY-TO-BAKE CHAPATTI DURING FROZEN STORAGEJOURNAL OF FOOD QUALITY, Issue 4 2009D.N. YADAV ABSTRACT The effect of prolonged frozen storage at ,18C, on the textural and sensory properties of ready-to-bake frozen chapatti (R-BFC) was evaluated. The R-BFC samples were prepared from normal- (control) and microwave-treated (18% moisture content for 80 s) wheat grains. Results showed that the extensibility of dough and maximum load for resistance increased gradually in both the samples during frozen storage; however, the increase was lesser in the treated ones. Chapattis prepared from both R-BFC samples exhibited higher hardness, cohesiveness, chewiness and lower springiness values during frozen storage. Microwave-treated R-BFC samples were rated as better retained in color, texture and overall acceptability scores as compared with control, up to 6 months of storage at ,18C. Thiamin and riboflavin contents were monitored during frozen storage and a loss of 12.0,14.5% in thiamin and 4,6% in riboflavin after 6 months of frozen storage was recorded. PRACTICAL APPLICATIONS During frozen storage, various physical, rheological and sensory changes occur in the food products, which determine the consumer's acceptability. The results of this study will help to establish quality of the frozen chapattis with respect to texture, color and aroma which will meet the consumer's acceptance. The protocol for the storage of frozen chapattis will help the industry to deliver the product of optimum quality. [source] RHEOLOGICAL AND PHYSICAL PROPERTIES OF DATE JUICE PALM BY-PRODUCT (PHOENIX DACTYLIFERA L.) AND COMMERCIAL XANTHAN GUMSJOURNAL OF TEXTURE STUDIES, Issue 2 2010RIADH BEN SALAH ABSTRACT Rheological and thermal properties of xanthan produced by Xanthomonas campestris from date by-products (DBP-xanthan) and commercial xanthan were determined. DBP-xanthan gave solutions with lower apparent viscosity than commercial xanthan. However, DBP-xanthan solutions were more stable to temperature changes and ionic strength than commercial xanthan. Gradual increase of storage modulus (G,) as function of frequency was observed for the two polysaccharides. On the other hand, loss modulus (G,) remained constant for DBP-xanthan and an increase was observed for commercial xanthan. Granulometric profile indicates that DPB-xanthan particle size was lower than commercial xanthan. Differential scanning calorimetry showed that the melting temperatures (Tm) and enthalpy (,Hm) of DBP-xanthan were higher than those of commercial xanthan. These properties of DBP-xanthan are quite rare among xanthan described in the literature and give this new gum great potential for use in the field of bioindustries as thickening and stabilizing agents. PRACTICAL APPLICATIONS Xanthan gum from date by-products (DBP-xanthan) was recently produced in our laboratory. No work has been undertaken to study the rheological properties of this polysaccharide to date. Rheological and some physicals properties were compared to those of commercial xanthan. This could promote industrial use of DBPs as low-cost natural source for xanthan gum production. [source] INFLUENCE OF HYDROXYPROPYL METHYLCELLULOSE ON THE RHEOLOGICAL AND MICROSTRUCTURAL CHARACTERISTICS OF WHOLE WHEAT FLOUR DOUGH AND QUALITY OF PURIJOURNAL OF TEXTURE STUDIES, Issue 2 2009M. L. SUDHA ABSTRACT Puri is a traditional unleavened fried product prepared from whole wheat flour. Hydroxypropyl methylcellulose (HPMC) was used to study its effect on rheological characteristics of whole wheat flour dough and puri making quality. Addition of HPMC at 0.5 and 1.0% w/w increased the water absorption and dough stability whereas the resistance to extension and extensibility decreased. Pasting temperature, peak viscosity and cold paste viscosity gradually decreased. The moisture and fat contents of puri increased marginally. Quality parameters and sensory acceptability were monitored after 0 and 8 h of storage. Addition of 0.5% HPMC gave higher sensory scores. Microscopic observations during puri processing showed that the starch granules in the control dough were clearly visible in the protein matrix, which reduced on frying due to partial gelatinization. Microstructure of puri with HPMC showed higher gelatinization of starch. It also helped in moisture retention and hence, resulted in highly pliable and soft-textured puri. PRACTICAL APPLICATIONS Puri is a traditional unleavened fried product that is prepared by mixing whole wheat flour and water, sheeted to a desirable thickness and fried. Use of hydroxypropyl methylcellulose (HPMC) affected the whole wheat flour dough and puri making quality. It helped in moisture retention and hence, resulted in highly pliable and soft-textured puri. Microstructure of puri with HPMC showed higher gelatinization of starch. [source] EFFECT OF HYDROTHERMAL TREATMENT ON THE PHYSICOCHEMICAL, RHEOLOGICAL AND OIL-RESISTANT PROPERTIES OF RICE FLOUR,JOURNAL OF TEXTURE STUDIES, Issue 2 2009DEOK NYUN KIM ABSTRACT Rice flour was thermomechanically modified by steam-jet cooking and the physicochemical, rheological and oil-resistant properties of the resulting product were characterized. Compared with native rice flour, the steam jet-cooked rice flour exhibited significantly increased hydration properties. Its pasting properties were also characterized by cold initial viscosity, decreased setback and the lack of peak viscosity. The shear-thinning behaviors of the steam jet-cooked rice flour were satisfactorily fitted into the Carreau equation. In addition, dynamic viscoelastic measurements showed that the liquid-like nature was more dominant over the solid-like properties. When incorporated into frying batter formulations, the steam jet-cooked rice flour increased the batter viscosity and pickup. The use of steam jet-cooked rice flour also enabled fried batters to control the moisture loss effectively. Furthermore, the wheat flour replacement with 20% steam jet-cooked rice flour in batters led to dramatic reduction of oil uptake by around 40%. PRACTICAL APPLICATIONS This study introduces a hydrothermal treatment (steam-jet cooking) as a new technique to impart better functional properties to rice flour. Specially, the steam jet-cooked rice flour exhibited oil-resisting properties when incorporated into frying batters, consequently producing fried foods with reduced content of oil and calorie. [source] PREDICTING TEXTURE ATTRIBUTES FROM MICROSTRUCTURAL, RHEOLOGICAL AND THERMAL PROPERTIES OF HAZELNUT SPREADSJOURNAL OF TEXTURE STUDIES, Issue 5 2008ROSSELLA DI MONACO ABSTRACT Eight trained assessors evaluated one visual, eight texture and four gustative attributes of 15 commercial spreads. In addition, 100 consumers evaluated the acceptability of the spreads. Rheological behavior of the samples was evaluated in transient (stress,relaxation test) and dynamic (strain and frequency sweep test) shear mode. Thermal measurements were also performed. Finally, the microstructure of the samples was analyzed by scanning electron microscopy. Partial least squares regression was used to predict acceptability from sensory attributes and texture from instrumental data. Scanning electron micrographs indicated that spreads differed in morphology, size and distribution of hazelnut particles. Overall liking of the spreads was found to be related to hazelnut flavor and texture attributes. Prediction of the most important texture properties from instrumental measurements was quite successful, especially for spreadability which was found negatively related to the consistency and flow indices and, secondly, for meltability which was found to be strongly dependent on measured thermal parameters. PRACTICAL APPLICATIONS This study contributes to knowledge development in the research area of acceptability, sensory and instrumental correlation for semi-solid foods. The results confirm that texture properties of spreadable foods play a most important role in consumer acceptability. The research also allows better understanding as to why no single measurement is able to predict all texture attributes adequately and why more appropriate tests need to be developed for an accurate prediction of some sensory attributes as perceived by the human senses. [source] RHEOLOGICAL, TEXTURAL AND MICROSTRUCTURE ANALYSIS OF THE HIGH-METHOXY PECTIN/GELATIN MIXED SYSTEMSJOURNAL OF TEXTURE STUDIES, Issue 5 2007H. LIU ABSTRACT The aim of this research was to evaluate the interaction between high-methoxy pectin and gelatin in solution and mixed gel utilizing rheological, texture profile and microstructure analysis. The results showed that the phase separation and association might both exist depending on the ratio of pectin to gelatin in the mixed system. After the pectin addition to the mixed system, the gelation properties of gelatin were improved at suitable conditions. The structure development rate, gel hardness and gel brittleness of the pectin/gelatin mixed system were positively affected by the addition of pectin and from there to expand the application of the mixed system in food industry. PRACTICAL APPLICATIONS Structure-forming polysaccharides and protein provide desired functional properties to a wide range of foods such as gel confectionery products, milk products and fat replacers. As an academic paper, this article provided the information that high-methoxy (HM) pectin could prove the gelation properties of gelatin to corporate audiences. We could find that the ratio of HM pectin to gelatin, and the concentration of these two polymers, dictate the texture properties of the mixed system. The pectin addition to the gelatin system affected the structure development rate, which might save time when the products are processed in practice. The melting temperature was increased with the pectin addition to the gelatin system, which is favorable if it is to be kept under higher temperature. [source] Rheological, textural and melting properties of commercial samples of some of the different types of pasteurized processed cheeseINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 2 2007YANJIE LU The detailed rheological and textural properties of commercially available samples of the three major categories of pasteurized processed cheese in the USA, that is, pasteurized process American cheese (PPA), pasteurized process cheese product (PPP) and pasteurized process cheese food (PPF), were analysed. All samples had similar pH values, ranging from 5.65 to 5.87, but most were ,5.7. Even within each of the categories considerable differences were observed in textural and melting behaviour. The samples with the lowest melt and the lowest loss tangent parameter from the rheological tests were two PPF and one PPA samples. These two PPF samples also had the highest hardness and adhesiveness force. Significant correlations were observed between several textural, rheological and melting properties. [source] Rheological, morphological, mechanical, and barrier properties of PP/EVOH blendsADVANCES IN POLYMER TECHNOLOGY, Issue 3 2001Jong Ho Yeo Using the biaxially oriented film process, polypropylene (PP)/ethylene-vinyl alcohol copolymer (EVOH) blends with an improved barrier property could be obtained by generating a laminar structure of the dispersed phase in the matrix phase. This laminar morphology, induced by biaxial orientation, was found to result in a significant increase in the oxygen barrier property of PP/EVOH (85/15) blends by about 10 times relative to the pure PP. In this study, compatibility in the PP/EVOH blend system was evaluated by investigating the influence of compatibilizer on the rheological, morphological, and mechanical properties of the blends. In addition, the effects of compatibilizer content, draw ratio, and draw temperature on the oxygen permeability and morphology of biaxially drawn blend films were also studied. It was revealed that an optimum amount of compatibilizer, maleic anhydride grafted PP, should be used to improve the barrier property of the PP/EVOH blends with a well-developed laminar structure. The draw ratio and draw temperature had a significant influence on the permeability of the blends. The blend films exhibited a more pronounced laminar structure when the blends were stretched biaxially under processing conditions of higher draw ratio and draw temperature, resulting in higher barrier properties. © 2001 John Wiley & Sons, Inc. Adv Polym Techn 20: 191,201, 2001 [source] Enhanced compatibility of PA6/POE blends by POE- g -MAH prepared through ultrasound-assisted extrusionJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010Tingting Xie Abstract The effects of POE- g -MAH, prepared through different methods, on morphology and properties of PA6/POE/POE- g -MAH blends are summarized in this article. The grafting degree of POE- g -MAH can be increased through the ultrasound-assisted extrusion. Experimental results showed that the addition of POE- g -MAH can increase the mechanical properties of the PA6/POE blend and decrease the particle size of POE dispersed phase in PA6 matrix due to the compatibilization by POE- g -MAH. The PA6/POE blend compatibilized by POE- g -MAH prepared through the ultrasound-assisted extrusion has smaller particle size of POE dispersed phase and higher notched Izod impact strength than that by POE- g -MAH with similar grafting degree initiated only by peroxide. This result is ascribed to some anhydride rings attached to the chain terminus of POE due to ultrasound initiation. Rheological and Molau test results also showed enhanced compatibilization of POE- g -MAH prepared through the ultrasound-assisted extrusion on the PA6/POE blend due to a structural difference of POE- g -MAH. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Rheological and thermal properties of poly(ethylene oxide)/multiwall carbon nanotube compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008T. N. Abraham Abstract Poly(ethylene oxide) (PEO) based nanocomposites were prepared by the dispersion of multiwall carbon nanotubes (MWCNTs) in aqueous solution. MWCNTs were added up to 4 wt % of the PEO matrix. The dynamic viscoelastic behavior of the PEO/MWCNT nanocomposites was assessed with a strain-controlled parallel-plate rheometer. Prominent increases in the shear viscosity and storage modulus of the nanocomposites were found with increasing MWCNT content. Dynamic and isothermal differential scanning calorimetry studies indicated a significant decrease in the crystallization temperature as a result of the incorporation of MWCNTs; these composites can find applications as crystallizable switching components for shape-memory polymer systems with adjustable switching temperatures. The solid-state, direct-current conductivity was also enhanced by the incorporation of MWCNTs. The dispersion level of the MWCNTs was investigated with scanning electron microscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Rheological and curing behavior of aqueous ambient self-crosslinkable polyacrylate emulsionJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Xiaohua Liu Abstract An aqueous ambient crosslinkable polymer acrylic (AACPA) emulsion was obtained by adding adipic acid dihydrazide (ADH) to the polyacrylate emulsion incorporating diacetone acrylamide (DAAM), and this emulsion was synthesized by two feeding materials methods. The AACPA emulsion and its paint film were characterized with rheological measurements, laser light scattering, Fourier transform infrared, torsional braid analysis (TBA), DTA, and so on. The results showed that AACPA emulsion was pseudoplastic fluid and pseudoplasticity increased with increasing of DAAM content. The results also showed that water resistance, solvent resistance, and thermotacky temperature of AACPA paint film increased with increasing of the content of DAAM. The results dealing with curing behavior of the paint film showed that adding organic swelling solvent and organic acid to the AACPA emulsion can accelerate the curing speed of the paint film. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Rheological and electrical properties of bentonite in anionic polystyrene sulfonate and nonionic poly(vinyl alcohol)JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Bassem A. Mostafa Abstract The flow properties of bentonite were studied with a combination of anionic polystyrene sulfonate (molecular weight = 70,000 g/mol) and nonionic poly(vinyl alcohol) (molecular weight = 50,000 g/mol). This combination had a significant effect on clay suspensions depending on the sequence of the polymer addition. The addition of 50 mg/L anionic polystyrene sulfonate followed by 200 mg/L nonionic poly(vinyl alcohol) improved the rheological properties with a 7% bentonite suspension, especially at 20°C and after 24 h of aging. However, by the reversal of this addition sequence, the rheological properties of bentonite suspensions were reduced. The , potential of bentonite suspensions of the individual polymers at the same concentration was ,42 mV for polystyrene sulfonate and ,63 mV for poly(vinyl alcohol). The combined effect of anionic polystyrene sulfonate followed by nonionic poly(vinyl alcohol) noticeably changed the , potential (,95 mV). With the reversal of the addition sequence, this parameter did not change. Potential energy profiles were constructed to investigate the suspension stability. Potential energy profiles of polystyrene sulfonate added to bentonite suspensions and followed by poly(vinyl alcohol) produced high repulsion potential energy between clay surfaces, reflecting high suspension stability. By the reversal of this sequence, a significant reduction of the energy barrier was observed. On the basis of the rheological and electrical properties of this system, the addition of polystyrene sulfonate followed by poly(vinyl alcohol) provides a promising tendency for a 7% clay concentration to meet desirable drilling mud properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3886,3894, 2007 [source] Rheological and Thermal Properties of Polylactide/Silicate Nanocomposites FilmsJOURNAL OF FOOD SCIENCE, Issue 2 2010Jasim Ahmed ABSTRACT:, Polylactide (DL)/polyethylene glycol/silicate nanocomposite blended biodegradable films have been prepared by solvent casting method. Rheological and thermal properties were investigated for both neat amorphous polylactide (PLA-DL form) and blend of montmorillonite (clay) and poly (ethylene glycol) (PEG). Melt rheology of the PLA individually and blends (PLA/clay; PLA/PEG; PLA/PEG/clay) were performed by small amplitude oscillation shear (SAOS) measurement. Individually, PLA showed an improvement in the viscoelastic properties in the temperature range from 180 to 190 °C. Incorporation of nanoclay (3% to 9% wt) was attributed by significant improvements in the elastic modulus (G,) of PLA/clay blend due to intercalation at higher temperature. Both dynamic modulii of PLA/PEG blend were significantly reduced with addition of 10% PEG. Rheometric measurement could not be conducted while PLA/PEG blends containing 25% PEG. A blend of PLA/PEG/clay (68/23/9) showed liquid-like properties with excellent flexibility. Thermal analysis of different clay loading films indicated that the glass transition temperatures (Tg) remained unaffected irrespective of clay concentration due to immobilization of polymer chain in the clay nanocomposite. PEG incorporation reduced the,Tg of the blend (PLA/PEG and PLA/PEG/clay) significantly. Both rheological and thermal analysis data supported plasticization and flexibility of the blended films. It is also interesting to study competition between PLA and PEG for the intercalation into the interlayer spacing of the clay. This study indicates that PLA/montmorillonite blend could serve as effective nano-composite for packaging and other applications. [source] Rheological and Functional Properties of Catfish Skin Protein HydrolysatesJOURNAL OF FOOD SCIENCE, Issue 1 2010Huaixia Yin ABSTRACT:, Catfish skin is an abundant and underutilized resource that can be used as a unique protein source to make fish skin protein hydrolysates. The objectives of this study were to isolate soluble and insoluble proteins from hydrolyzed catfish skin, study the rheological and functional properties of the protein hydrolysates, and evaluate the properties of emulsions made from the protein powders. Freeze-dried catfish skin soluble (CSSH) and insoluble hydrolysate (CSISH) powders were analyzed for proximate analysis, emulsion stability, fat absorption, amino acids, color, and rheological properties. CSSH had significantly (P,< 0.05) higher protein, ash, and moisture content but lower fat content than that of CSISH. The yield of CSSH (21.5%± 2.2%) was higher than that of CSISH (3%± 0.3%). CSISH had higher emulsion stability than CSSH. CSSH was light yellow in color and CSISH was darker. The mean flow index values for emulsion containing CSSH (ECSSH) and CSISH (ECSISH) were both less than 1, indicating that they were both pseudoplastic fluid. The G, and G, values for the ECSISH were higher than that of ECSSH, indicating that the viscoelastic characteristic of the emulsion containing CSISH was greater than that of the emulsion containing CSSH. The study demonstrated the CSSH and CSISH had good functional and rheological properties. They have potential uses as functional food ingredients. [source] Effect of Heat-Moisture Treatment and Acid Modification on Rheological, Textural, and Differential Scanning Calorimetry Characteristics of Sweetpotato StarchJOURNAL OF FOOD SCIENCE, Issue 6 2005Sukhcharn Singh ABSTRACT Sweetpotato starches were characterized to understand the changes upon modification by acid and heat-moisture treatment (HMT) in the rheological, differential scanning calorimetry (DSC), and textural characteristics of starch isolated from the sweetpotato variety PSP-21 and to compare these findings with those of commercially available arrowroot starch. The native sweetpotato starch had a Type A pasting profile characterized by a high peak viscosity (PV) (741.5 rapid viscoanalyzer unit [rvu]), with a high breakdown (378.8 rvu) and low cold paste viscosity (CPV) (417.6 rvu). After HMT, there was a marked decrease in the PV (639.1), a very slight breakdown (113.5 rvu) and an increase in CPV (759.5 rvu), more like a Type C pasting profile. However, acid modification did not notably change the pasting profile of native sweetpotato starch. The DSC characteristics were also affected significantly after modifications. The gelatinization temperature parameter to onset (To) decreased significantly after HMT and acid modification. The gelatinization enthalpy decreased during HMT from 15.98 to 14.42 J/g. The gel strength of acid-modified starch was the highest compared with that of HMT and native sweetpotato and arrowroot starches. [source] RHEOLOGICAL AND PHYSICAL PROPERTIES OF DATE JUICE PALM BY-PRODUCT (PHOENIX DACTYLIFERA L.) AND COMMERCIAL XANTHAN GUMSJOURNAL OF TEXTURE STUDIES, Issue 2 2010RIADH BEN SALAH ABSTRACT Rheological and thermal properties of xanthan produced by Xanthomonas campestris from date by-products (DBP-xanthan) and commercial xanthan were determined. DBP-xanthan gave solutions with lower apparent viscosity than commercial xanthan. However, DBP-xanthan solutions were more stable to temperature changes and ionic strength than commercial xanthan. Gradual increase of storage modulus (G,) as function of frequency was observed for the two polysaccharides. On the other hand, loss modulus (G,) remained constant for DBP-xanthan and an increase was observed for commercial xanthan. Granulometric profile indicates that DPB-xanthan particle size was lower than commercial xanthan. Differential scanning calorimetry showed that the melting temperatures (Tm) and enthalpy (,Hm) of DBP-xanthan were higher than those of commercial xanthan. These properties of DBP-xanthan are quite rare among xanthan described in the literature and give this new gum great potential for use in the field of bioindustries as thickening and stabilizing agents. PRACTICAL APPLICATIONS Xanthan gum from date by-products (DBP-xanthan) was recently produced in our laboratory. No work has been undertaken to study the rheological properties of this polysaccharide to date. Rheological and some physicals properties were compared to those of commercial xanthan. This could promote industrial use of DBPs as low-cost natural source for xanthan gum production. [source] Acrylic Triblock Copolymer Design for Thermoreversible Gelcasting of Ceramics: Rheological and Green Body PropertiesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2009M. E. Seitz Thermoreversible gelcasting (TRG) is an attractive net-shape powder-based processing technique which relies on the temperature-driven gelation of a polymer solution. This study uses the TRG of alumina to investigate the implications of triblock copolymer design (block length, endblock fraction, and midblock chemistry) on rheological and green body properties. The liquid-to-solid transition and relaxation time in the gel state are controlled by the polymer's endblock length while the total polymer length controls the viscosity at high temperature. Although triblock design and concentration do not affect the green body porosity or sintered density, they do have significant effects on green body behavior. Triblocks with a high fraction of rubbery midblock behave as elastomers and confer significant toughness to the green bodies. In contrast, those with glassy midblocks increase the strength of the body but also behave in a brittle manner. Green body strength increases with increasing triblock concentration and is well described by a model for the strength of ceramic bodies with the binder localized at the particle necks. [source] Compatibilizing effect of ethylene,propylene,diene grafted maleic anhydride terpolymer on the blend of polyamide 66 and thermal liquid crystalline polymerPOLYMER COMPOSITES, Issue 6 2006Qunfeng Yue Polyamide 66,thermal liquid crystalline polymer (PA66/TLCP) composites containing 10 wt% TLCP was compatibilized by ethylene,propylene,diene-grafted maleic anhydride terpolymer (MAH- g -EPDM). The blending was performed on a twin-screw extrusion, followed by an injection molding. The rheological, dynamic mechanical analysis (DMA), thermal, mechanical properties, as well as the morphology and FTIR spectra, of the blends were investigated and discussed. Rheological, DMA, and FTIR spectra results showed that MAH- g -EPDM is an effective compatibilizer for PA66/TLCP blends. The mechanical test indicated that the tensile strength, tensile elongation, and the bending strength of the blends were improved with the increase of the content of MAH- g -EPDM, which implied that the blends probably have a great frictional shear force, resulting from strong adhesion at the interface between the matrix and the dispersion phase; while the bending modulus was weakened with the increase of MAH- g -EPDM content, which is attributed to the development of the crystalline phase of PA66 hampered by adding MAH- g -EPDM. POLYM. COMPOS., 27:608,613, 2006. © 2006 Society of Plastics Engineers [source] Improved properties of blends of ultrasonically treated unfilled polyurethane rubberPOLYMER ENGINEERING & SCIENCE, Issue 4 2004Sayata Ghose The aim of this investigation is to improve the properties of the polyurethane rubber that has been devulcanized using the coaxial ultrasonic reactor. After devulcanization of the cured rubber under varying gap sizes and amplitudes, blends of the devulcanized and virgin rubber at different ratios are prepared. Rheological and mechanical properties, hardness as well as gel fraction and crosslink density of the vulcanized blends have been investigated. Results show that compared to the vulcanizates of the devulcanized samples, the vulcanizates of the blends show a remarkable improvement in properties, which are sometimes comparable to or even better than the virgin vulcanizate. Blends have also prepared using different proportions of ground samples and virgin rubber, and a comparison of properties between these blends and the blends of the devulcanized rubber has been carried out. The results show that compared to the ground samples, the blends of the devulcanized samples are easier to mix and exhibit enhanced and more uniform properties. Polym. Eng. Sci. 44:794,804, 2004. © 2004 Society of Plastics Engineers. [source] Rheological determinants of red blood cell aggregation in diabetic patients in relation to their metabolic controlDIABETIC MEDICINE, Issue 2 2002K. Elishkevitz Abstract Aims To determine whether increased red blood cell adhesiveness/aggregation in diabetic patients is related to the extent of their metabolic control. Methods We measured erythrocyte adhesiveness/aggregation in a group of 85 adult patients with diabetes mellitus by using citrated venous whole blood and a simple slide test. The erythrocyte adhesiveness/aggregation was determined by measuring the size of the spaces that are formed between the aggregated erythrocytes. We divided the patients into those with either low or high erythrocyte adhesiveness/aggregation values. Results The erythrocyte adhesiveness/aggregation values of the two groups differed significantly in terms of their fibrinogen concentration, erythrocyte sedimentation rate, high sensitive C-reactive protein (CRP), total cholesterol and triglyceride concentrations. There was no difference between the two groups regarding the concentrations of HbA1c. Logistic regression was applied to construct a model to predict the belonging of a patient in the low or high erythrocyte adhesiveness/aggregation group. A linear regression was applied to construct a model to predict the erythrocyte adhesiveness/aggregation values. Both models turned out to include gender, age, fibrinogen, triglyceride, retinopathy, coronary artery disease and age and gender interaction. Neither HbA1c nor CRP entered the models. Conclusions The degree of erythrocyte adhesiveness/aggregation and several variables of the acute-phase response in patients with diabetes mellitus are not directly related to the degree of metabolic control as evaluated by means of HbA1c concentration. Diabetic patients might benefit from rheological or anti-inflammatory interventions regardless of their metabolic control. [source] Rheological, textural and melting properties of commercial samples of some of the different types of pasteurized processed cheeseINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 2 2007YANJIE LU The detailed rheological and textural properties of commercially available samples of the three major categories of pasteurized processed cheese in the USA, that is, pasteurized process American cheese (PPA), pasteurized process cheese product (PPP) and pasteurized process cheese food (PPF), were analysed. All samples had similar pH values, ranging from 5.65 to 5.87, but most were ,5.7. Even within each of the categories considerable differences were observed in textural and melting behaviour. The samples with the lowest melt and the lowest loss tangent parameter from the rheological tests were two PPF and one PPA samples. These two PPF samples also had the highest hardness and adhesiveness force. Significant correlations were observed between several textural, rheological and melting properties. [source] Effect of different starches on rheological and microstructural properties of (II) commercial processed cheeseINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 12 2008Darshan Trivedi Summary A range of commercial processed cheese samples containing starch were prepared on a Rapid Visco Analyser (RVA) and on a pilot plant scale. This work clearly demonstrated that it was possible to manufacture processed cheese with part of the protein replaced with potato starch, while maintaining similar rheological attributes (firmness) to those of the control and an acceptable melt index. Sensory evaluation showed that, although the reduced-protein cheese samples had a good, clean, fresh flavour that was comparable with that of the control, at high starch concentrations the starch-containing processed cheese had a pasty texture and tended to stick to the wrapper. [source] Studies on the quality of Turkish flat breads based on blends of triticale and wheat flourINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 5 2005kuner Summary The effect of different levels of triticale flour on the rheological and sensory characteristics of a range of Turkish flat breads made with blends of triticale with two bread wheat cultivars (K,nac, 97 and Daǧda, 94) was studied. Wheat flour was replaced with triticale flour at 20, 40, 50, 60 and 80% levels. Bread samples were tested for shape and symmetry, crust colour, crumb colour and structure, mouth-feel, taste and aroma and flexibility. All bread types had high overall sensory scores and they were considered acceptable. Analysis of variance (anova) and principal component analysis (PCA) showed that Daǧda, 94 and Triticale blends are more suitable than K,nac, 97 and Triticale blends for bazlama, yufka and lavash production. Results show that Triticale-wheat flour blends can be successfully used for the production of flat breads. Dough and sensory properties of triticale-wheat flour blends were highly cultivar specific and dependent on blend proportion. [source] Effect of manufacturing treatments on the rheological character of Mozzarella cheese made from microfiltration retentate depleted of whey proteins,INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2001Randall L. Brandsma Low-moisture, part-skim (LMPS) Mozzarella cheeses were made from highly concentrated skim milk microfiltration (MF) retentate and butteroil. Differing combinations of rennet concentration, coagulation temperature and post-coagulation curd cutting time were used, with comparisons made of the rheological and functional characteristics of cheeses during ageing. Lubricated squeezing flow, stress relaxation, melt and stretch measurements demonstrated that commercial LMPS Mozzarella had substantial textural and functional change between 7 and 30 days of age, while the rheological and functional behaviour of LMPS MF Mozzarella (MFM) exhibited substantial change between 30 and 60 days of age. Rennet concentration was the only experimental factor to significantly affect MFM rheological and functional development. The delayed development of MFM was partially attributed to inhibition of normal cheese proteolysis via whey protein (WP) incorporation, lack of starter culture protease, and homogenization of MF cheesemilk. Use of starter culture in MFM led to improved rheological and functional behaviour. [source] Rheological, morphological, mechanical, and barrier properties of PP/EVOH blendsADVANCES IN POLYMER TECHNOLOGY, Issue 3 2001Jong Ho Yeo Using the biaxially oriented film process, polypropylene (PP)/ethylene-vinyl alcohol copolymer (EVOH) blends with an improved barrier property could be obtained by generating a laminar structure of the dispersed phase in the matrix phase. This laminar morphology, induced by biaxial orientation, was found to result in a significant increase in the oxygen barrier property of PP/EVOH (85/15) blends by about 10 times relative to the pure PP. In this study, compatibility in the PP/EVOH blend system was evaluated by investigating the influence of compatibilizer on the rheological, morphological, and mechanical properties of the blends. In addition, the effects of compatibilizer content, draw ratio, and draw temperature on the oxygen permeability and morphology of biaxially drawn blend films were also studied. It was revealed that an optimum amount of compatibilizer, maleic anhydride grafted PP, should be used to improve the barrier property of the PP/EVOH blends with a well-developed laminar structure. The draw ratio and draw temperature had a significant influence on the permeability of the blends. The blend films exhibited a more pronounced laminar structure when the blends were stretched biaxially under processing conditions of higher draw ratio and draw temperature, resulting in higher barrier properties. © 2001 John Wiley & Sons, Inc. Adv Polym Techn 20: 191,201, 2001 [source] Compatibilization and development of layered silicate nanocomposites based of unsatured polyester resin and customized intercalation agentJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Luigi Torre Abstract In this study a procedure for the preparation of compatibilized nanoclays was used to produce effective nanocomposites based on unsatured polyester (UP) resin. A compatibilization procedure of the filler with a selected surfactant has been developed and optimized, the effect of organic modifiers on the synthesized nanocomposites properties was studied. Moreover, polyester/clay nanocomposites were prepared. In particular, samples were prepared using two different mixing methods. The properties and formation processes of the nanocomposites obtained using the two methods were compared. X-ray diffraction studies revealed the formation of intercalated/exfoliated nanocomposites structures. The effect of processing parameters, used for both the compatibilization procedure and the preparation of nanocomposites, was studied. Dynamic mechanical, thermal analysis, and rheological tests were performed to investigate the formation mechanism of UP/montmorillonite nanocomposite. In particular, mechanical properties of nanocomposites were studied using dynamic mechanical analysis and tensile tests. Mechanical, rheological, and thermal characterization have confirmed the validity of the used approach to compatibilize the nanoclay and to produce nanocomposites. Tensile strength and Young's modulus were modified by the loading of the organoclays. Furthermore, the rheology of the nanocomposite formulation provided processing information, while mechanical and dynamic mechanical characterization was performed on the nanocomposites produced with the newly compatibilized formulation. The results have shown that nanocomposites with better mechanical properties can be obtained through the selection of an appropriate compatibilization process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] The properties of reactive hot melt polyurethane adhesives modified with novel thermoplastic polyurethanesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2009Tae K. Kim Abstract A reactive hot melt adhesive (RHMA) consisting of thermoplastic polyurethane (TPU) was modified with sodium montmorillonite (Na-MMT) intercalated with poly(ethylene glycol) (PEG), and their effects on the adhesion, rheological, and mechanical properties of the RHMA were examined. The Na-MMT intercalated with PEG (Na-MMT/PEG) effectively enhanced the initial bond strength development of the RHMA, although the amounts of Na-MMT/PEG in the RHMA were less than 0.2%. The increase of the complex viscosity and pseudo-solid like behavior observed at low shear rate indicates that there are intimate interactions between the RHMA molecules and Na-MMT/PEG. The improved modulus and tensile strength of the cured RHMA film in the presence of Na-MMT/PEG demonstrates that Na-MMT/PEG effectively reinforced the RHMA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Morphology, mechanical properties, and thermal stability of poly(L -lactic acid)/poly(butylene succinate- co -adipate)/silicon dioxide compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2009Ruyin Wang Abstract Poly(butylene succinate- co -adipate) (PBSA) and two types of SiO2 (hydrophilic or hydrophobic) were used to modify poly(L -lactic acid) (PLLA). The mechanical properties, rheological and thermal behavior, phase morphology, and thermal stability of PLLA/PBSA/SiO2 composites were investigated. The impact strength, flexural strength, and modulus of PLLA/PBSA blends increased after the addition of hydrophobic SiO2 without decreasing the elongation at break, and the elongation at break monotonically decreased with increasing hydrophilic SiO2 content. The melt elasticity and viscosity of the PLLA/PBSA blend increased with the addition of SiO2. The hydrophilic SiO2 was encapsulated by the dispersed PBSA phase in the composites, which led to the formation of a core,shell structure, whereas the hydrophobic SiO2 was more uniformly dispersed and mainly located in the PLLA matrix, which was desirable for the optimum reinforcement of the PLLA/PBSA blend. The thermogravimetric analysis results show that the addition of the two types of SiO2 increased the initial decomposition temperature and activation energy and consequently retarded the thermal degradation of PLLA/PBSA. The retardation of degradation was prominent with the addition of hydrophobic SiO2. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Preparation of poly(acrylonitrile,butadiene,styrene)/montmorillonite nanocomposites and degradation studies during extrusion reprocessingJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2009E.-K. Karahaliou Abstract In this study, the preparation of organically modified montmorillonite/poly(acrylonitrile,butadiene,styrene) (ABS) nanocomposites was studied by melt blending in a twin-screw extruder. The composite material was subjected to a series of five extrusion cycles, and the effect of reprocessing on the material's structural properties was investigated. More specifically, chemical changes were studied with attenuated total reflectance/Fourier transform infrared analysis, the thermal response was recorded by differential scanning calorimetry experiments, and the thermal stability was detected with thermogravimetric analysis. Also, the rheological properties of these blends were investigated via melt flow index tests as a measure of their processability during melt mixing and molding processes. Furthermore, the mechanical strength of the obtained mixtures was explored, and the observed interactions were interpreted in terms of the influence of each component on the functional properties of the final mixture. This attempt enriched our knowledge about the recycling of ABS, with the additional aspect of the use of collected data from more complex systems, that is, composite materials, where the montmorillonite nanoparticles play a role in the interactions initiated by repeated processing. The experimental results of this study show that the reprocessing of ABS/montmorillonite induced oxidation products, but the rheological, mechanical, and thermal properties and the thermal and color stabilities of the composites remained almost stable. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Investigation of the ultradrawing properties of gel spun fibers of ultra-high molecular weight polyethylene/carbon nanotube blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Jen-Taut Yeh Abstract The carbon nanotubes (CNTs) contents, ultrahigh-molecular-weight polyethylene (UHMWPE) concentrations and temperatures of UHMWPE, and CNTs added gel solutions exhibited significant influence on their rheological and spinning properties and the drawability of the corresponding UHMWPE/CNTs as-prepared fibers. Tremendously high shear viscosities (,s) of UHMWPE gel solutions were found as the temperatures reached 140°C, at which their ,s values approached the maximum. After adding CNTs, the ,s values of UHMWPE/CNTs gel solutions increase significantly and reach a maximum value as the CNTs contents increase up to a specific value. At each spinning temperature, the achievable draw ratios obtained for UHMWPE as-prepared fibers prepared near the optimum concentration are significantly higher than those of UHMWPE as-prepared fibers prepared at other concentrations. After addition of CNTs, the achievable draw ratios of UHMWPE/CNTs as-prepared fibers prepared near the optimum concentration improve consistently and reach a maximum value as their CNTs contents increase up to an optimum value. To understand these interesting drawing properties of the UHMWPE and UHMWPE/CNTs as-prepared fibers, the birefringence, thermal, morphological, and tensile properties of the as-prepared and drawn fibers were investigated. Possible mechanisms accounting for these interesting properties are proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] | |||||||||||||||||||