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Rheological Study (rheological + study)
Selected AbstractsRheological study of ternary mixtures and pectic gels of red fruit pulpsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2007Charles Windson Isidoro Haminiuk Summary In this work, the rheological behaviour of ternary mixtures of strawberry, blackberry and raspberry pulps in steady shear was studied using the response surface methodology. In addition, the rheology of pectic gels extracted from these pulps was investigated by means of oscillatory shear tests. The flow curves were adequately described by the rheological model of Herschel,Bulkley. All the formulations analysed exhibited shear-thinning behaviour. The rheological responses were influenced by the difference in pulp proportions and also by the temperatures (20 and 60 °C). The quadratic and cubic models used to fit the response were considered suitable owing to the higher values of determination coefficient (R2). The pectic gels from strawberry, blackberry and raspberry showed a strong gel character, with strawberry presenting the stronger gel, which was confirmed by the Cox,Merz experiment, degree of esterification and average molecular weight data. [source] Toughening of recycled polystyrene used for TV backsetJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Xiaoting Fu Abstract The recycled polystyrene (rPS) was toughened with ethylene-octylene copolymer thermoplastic elastomer (POE) and high-density polyethylene (HDPE) with various melt flow index (MFI), compatibilized by styrene-butadiene-styrene copolymer (SBS) to enhance the toughness of rPS for use as TV backset. The rPS/POE binary blends exhibited an increased impact strength with 5,10 wt % POE content followed by a decrease with the POE content up to 20 wt %, which could be due to poor compatibility between POE and rPS. For rPS/POE/SBS ternary blends with 20 wt % of POE content, the impact strength increased dramatically and a sharp brittle-ductile transition was observed as the SBS content was around 3,5 wt %. Rheological study indicated a possible formation of network structure by adding of SBS, which could be a new mechanism for rPS toughening. In rPS/POE/HDPE/SBS (70/20/5/5) quaternary blends, a fibril-like structure was observed as the molecular weight of HDPE was higher (with lower MFI). The presence of HDPE fibers in the blends could not enhance the network structure, but could stop the crack propagation during fracture process, resulting in a further increase of the toughness. The prepared quaternary blend showed an impact strength of 9.3 kJ/m2 and a tensile strength of 25 MPa, which can be well used for TV backset to substitute HIPS because this system is economical and environmental friendly. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] DEVELOPMENT OF A SOY-BASED CREAM CHEESEJOURNAL OF TEXTURE STUDIES, Issue 6 2008MUSFIRAH ZULKURNAIN ABSTRACT Various amounts of blended tofu, oil, salt, carrageenan, pectin and maltodextrin were used to develop soy cream cheese products that were trans fat free, with texture properties similar to those of commercial dairy cream cheese. Response surface methodology predicted three formulations with similar spreadability value of that obtained from commercial cheese. Carrageenan and salt were useful to impart the desired firmness, while maltodextrin provided body to the product. Pectin introduced viscous behavior to the final texture but was proven useful in preventing syneresis. Rheological study at 25 and 4C manifested that, although the developed products mimicked the texture of the commercial sample, they had less elasticity. Chemical analysis revealed that the soy cream cheeses had lower fat and higher protein and fiber contents than the commercial sample. They were also stable against syneresis and oil separation over storage of 20 days. PRACTICAL APPLICATIONS The production of soy-based products as alternatives to dairy products has attracted much attention recently. In addition to their lactose-free and reduced fat content, soy-based products are also a good source of protein. There has yet to be any published data on the development of a soy-derivative cream cheese. This paper emphasizes the rheological development of soy cream cheeses in the presence of food hydrocolloids. Their main and interaction effects on texture properties were assessed to mimic those of dairy cream cheese. A comprehensive and systematic approach of formulating the soy cream cheeses was applied by using response surface methodology. In addition, the chemical and nutritional properties of the products were also evaluated and compared with those of the commercial dairy counterpart. [source] Biodegradable nanocomposites from maleated polycaprolactone/soy protein isolate blend with organoclay: Preparation, characterization, and propertiesPOLYMER COMPOSITES, Issue 6 2009Abhisek Sasmal New biobased, eco-friendly nanocomposites were prepared from maleated polycaprolactone/soy protein isolate blend (50/50 wt/wt) with organo-modified clay by melt compounding. The XRD, TEM, tensile, DMTA, and rheological properties of the nanocomposites were investigated. X-ray diffraction and transmission electron microscopy analysis revealed that the intercalated nanocomposite is formed and the silicate layers of the clay are uniformly dispersed at a nanometer scale in the polymer matrix. There is a great enhancement in tensile and dynamic mechanical properties of the nanocomposites. Rheological study revealed that the nanocomposite exhibits strong shear thinning behavior and clay particles form network in the melted state of the composites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Heating-induced conformational change of a novel ,-(1,3)- D -glucan from Pleurotus geestanusBIOPOLYMERS, Issue 2 2010Mei Zhang Abstract Recently, we isolated and purified a neutral polysaccharide (PGN) from edible fungus Pleurotus geestanus. Its structure was characterized by a range of physical,chemical methods, including high performance anion exchange chromatography, uronic acid, and protein analyses, size exclusion chromatography with ultraviolet, refractive index and light scattering detectors, and nuclear magnetic resonance. Our results revealed that PGN is a novel ,-(1,3)- D -glucan with glucose attached to every other sugar residues at Position 6 in the backbone. It has a degree of branching of 1/2. Such structure is different from typical ,-(1,3)- D -glucans schizophyllan and lentinan in which DB is 1/3 and 2/5, respectively. Rheological study showed a very interesting melting behavior of PGN in water solution: heating PGN in water leads to two transitions, in the range of 8,12.5°C and 25,60°C, respectively. The melting behavior and conformational changes were characterized by rheometry, micro-differential scan calorimetry, atomic force microscopy, static and dynamic light scattering at different temperatures. The first heating-induced transition corresponds to the disintegration of polymer bundles into small helical clusters, resembling the heating-induced dissociation of SPG in water at 7°C; the second one might correspond to the dissociation of helical strands to individual chains. The ability of PGN to undergo a conformation/viscosity transition in water upon heating is very valuable to immobilize cells or enzymes or therapeutic DNA/RNA, which makes PGN a potentially useful biomaterial. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 121,131, 2010. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Effect of Chain Straightening on Plateau Modulus and Entanglement Molecular Weight of Ni-diimine Poly(1-hexene)sMACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2006Zhibin Ye Abstract Summary: In this communication, we report the first rheological study on the chain-straightened Ni-diimine poly(1-hexene)s and investigate the unique effect of chain straightening on plateau modulus and entanglement molecular weight of this series of polymers. Two Ni-diimine poly(1-hexene) samples having different levels of chain straightening were prepared with a chain-walking Ni-diimine catalyst, (ArNC(An)C(An)NAr)NiBr2 (An,=,acenaphthene, Ar,=,2,6-(i -Pr)2C6H3) at two different temperatures. Rheological analyses show that the chain-straightened polymers exhibit significantly enhanced plateau modulus and reduced entanglement molecular weight compared to regular poly(1-hexene)s by metallocene catalysis. Such an effect becomes more pronounced with an increase in the level of chain straightening. Loss moduli G,(,) versus reduced angular frequency in a linear, natural logarithm plot for the three polymers at the reference temperature of 100,°C. [source] | |||||||||||||