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Plateau Modulus (plateau + modulus)

Distribution by Scientific Domains

Polymers and Materials Science	66%

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]

Effect of Comonomer Ethylene on Plateau Modulus of Crystal-line Ethylene-propylene Random Copolymer with Broad Molecular Weight Distribution

CHINESE JOURNAL OF CHEMISTRY, Issue 6 2005
Ding Jian
Abstract Ethylene-propylene random copolymer with ultra-high molecular weight (UHPPR) and broad molecular weight distribution (MWD) was prepared with Ziegler-Natta catalyst. The viscoelastic behavior of UHPPR has been investigated by means of oscillatory rheometer at 180, 200 and 220 °C. The loss modulus (G, curves of 180 and 200 °C present a pronounced maximum at 38.10 and 84.70 r/s, respectively. For the first time, this makes it possible to directly determine the plateau modulus () of crystalline ethylene-propylene random copolymer with broad MWD in a certain experimental temperature G,(,) curve. The plateau modulus of UHPPR is 4.51×105 and 3.67×105 Pa at 180 and 200 °C respectively, increasing with random incorporation of comonomer ethylene into the molecular chains and being independent of molecular weight. [source]

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

Preparation and characteristics of nitrile rubber (NBR) nanocomposites based on organophilic layered clay

POLYMER INTERNATIONAL, Issue 7 2003
Jin-tae Kim
Abstract The effect of clay modification on organo-montmorillonite/NBR nanocomposites has been studied. Organo-montmorillonite/NBR nanocomposites were prepared through a melt intercalation process. NBR nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic mechanical thermal analysis (DMTA) and a universal testing machine (UTM). XRD showed that the basal spacing in the clay increased, which means that the NBR matrix was intercalated in the clay layer galleries. On TEM images, organo-montmorillonite (MMT) particles were clearly observed, having been exfoliated into nanoscale layers of about 10,20 nm thickness from their original 40 µm particle size. These layers were uniformly dispersed in the NBR matrix. The DMTA test showed that for these nanocomposites the plateau modulus and glass transition temperature (Tg) increased with respect to the corresponding values of pure NBR (without clay). UTM test showed that the nanocomposites had superior mechanical properties, ie strength and modulus. These improved properties are due to the nanoscale effects and strong interactions between the NBR matrix and the clay interface. Copyright © 2003 Society of Chemical Industry [source]

Viscoelastic properties of branched polyacrylate melts

POLYMER INTERNATIONAL, Issue 6 2001
Nasir M Ahmad
Abstract The viscoelastic properties of poly(n-butyl acrylate), poly(ethyl acrylate) and poly(methyl acrylate) melts have been studied using samples that varied in both molar mass and the mol% branched repeat units, these properties having been previously determined by gel permeation chromatography and 13C NMR spectroscopy, respectively. Poly(n-butyl acrylate) was studied most extensively using seven samples; one sample of poly(n-butyl acrylate), two samples of poly(ethyl acrylate) and one sample of poly(methyl acrylate) were used to study the effect of side-group size. Storage and loss moduli were measured over a range of frequency (1,×,10,3 to 1,×,102,rad,s,1) at temperatures from Tg,+,20,°C to Tg,+,155,°C and then shifted to form master curves at Tg,+,74,°C through use of standard superposition procedures. The plateau regions were not distinct due to the broad molar mass distributions of the polyacrylates. Hence, the upper and lower limits of shear storage modulus from the nominal ,plateau' region of the curves for the seven poly(n-butyl acrylate) samples were used to calculate the chain molar mass between entanglements, Me, which gave the range 13.0,kg,mol,1,<,Me,<,65.0,kg,mol,1. The Graessley,Edwards dimensionless interaction density and dimensionless contour length concentration were calculated for poly(n-butyl acrylate) using the mean value of plateau modulus (1.2,×,105,Pa) and three different methods for estimation of the Kuhn length; the data fitted closely to the Graessley,Edwards universal plot. The Williams,Landel,Ferry C1 and C2 parameters were determined for each of the polyacrylates; the data for the poly(n-butyl acrylate) samples indicate an overall reduction in C1 and C2 as the degree of branching increases. Although the values of C1 and C2 were different for poly(n-butyl acrylate), poly(ethyl acrylate) and poly(methyl acrylate), there is no trend for variation with structure. Thus the viscoelastic properties of the polyacrylate melts are similar to those for other polymer melts and, for the samples investigated, the effect of molar mass appears to dominate the effect of branching. © 2001 Society of Chemical Industry [source]