			Home About us Contact

Modulus G (modulus + g)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Effect of Chain Straightening on Plateau Modulus and Entanglement Molecular Weight of Ni-diimine Poly(1-hexene)s

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2006
Zhibin 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]

FEM-Simulation of Real and Artificial Microstructures of Mo-Si-B Alloys for Elastic Properties and Comparison with Analytical Methods,

ADVANCED ENGINEERING MATERIALS, Issue 10 2007
G. Biragoni
Various three phase microstructures of Mo-Si-B alloys were simulated in tensile loading conditions using a 2D finite element method to predict the elastic properties of the composite material. Voronoi structures with the same areal fraction of phases as the real microstructures have been generated and simulated similarly. Also, with these Voronoi structures a variation of grain or phase sizes, respectively, was carried out for different compositions in order to study on the elastic properties of the composite. Finally, a comparison was made over the whole temperature range between the above numerical methods, classical analytical approaches and experimentally determined values for Young's modulus E, shear modulus G and Poisson's ratio ,. [source]

The effect of long-term frozen storage on the quality of frozen and thawed mashed potatoes with added cryoprotectant mixtures

INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2009
Cristina Fernández
Summary Cryoprotectant mixtures were added to frozen/thawed (F/T) mashed potatoes in the form of amidated low-methoxyl (ALM) pectin and xanthan gum (XG), kappa-carrageenan (,-C) and XG and sodium caseinate (SC) and XG, and the effect of frozen storage was examined. F/T mashed potatoes without added biopolymers had higher storage modulus G, after freezing and frozen storage, associated with sponge formation due to amylose retrogradation. Oscillatory measurements indicated weakening of the structure of mashed potatoes without biopolymers and with added ,-C/XG and SC/XG mixtures at the end of storage due to ice recrystallisation, whereas the structure of samples with added ALM/XG mixtures was reinforced by increasing time in storage. Mashed potatoes with added mixtures exhibited water-holding capacity for 1 year. Samples with added ,-C/XG mixtures were more structured, although when both ,-C/XG and SC/XG mixtures were included in mashed potato, very acceptable sensory quality was maintained in usual frozen storage conditions. [source]

A Study of the Use of Oscillatory Flow to Characterize Isotactic and Syndiotactic Poly(propylene)s

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 19 2006
Elena Rojo
Abstract Summary: A rheological characterization of poly(propylene)s (PP) of different tacticity, monomodal and bimodal molecular distribution and long chain branching (LCB), is presented. Loss factor , plotted as a function of the complex modulus G* allows to discriminate syndiotactic from isotactic PPs, as well as syndiotactic monomodal from bimodal samples. However, using such rheological plots is not effective to investigate the broadness of the molecular weight distribution and other rheological techniques are proposed. Isotactic and syndiotactic PPs submitted to electro beam irradiation give rise to thermorheological complexity, associated to LCB. The degree of LCB is estimated using complex viscosity results. Syndiotactic poly(propylene)s are more prone to give long branches than isotactic samples. A symptom of long chain branching is detected in irradiated syndiotactic PPs. [source]