Some Aspects of the Relationship between Molecular Structure and Flow Behavior of Polymer Melts

1969 ◽  
Vol 42 (3) ◽  
pp. 823-834 ◽  
Author(s):  
L. L. Blyler
Keyword(s):  
Molecular Structure ◽  
Activation Energy ◽  
Molecular Weight ◽  
Molecular Mechanisms ◽  
Flow Behavior ◽  
Average Molecular Weight ◽  
Melt Fracture ◽  
Flow Activation Energy ◽  
Shear Dependent Viscosity ◽  
Dependent Viscosity

Abstract The shear dependent viscosity and related properties of a number of ethylene polymers of differing molecular structure have been characterized using a capillary extrusion rheometer. The structural aspects of interest were average molecular weight, branching, and the presence of strong intermolecular secondary forces. It was found that average molecular weight influences the degree of shear dependence of the viscosity, branching affects both flow activation energy and the nature of the observed “melt fracture” phenomenon, and intermolecular hydrogen bonding enhances viscosity and activation energy and leads to increased shear dependence of flow behavior. The results are interpreted in terms of specific molecular mechanisms.

Flow Behavior of Heterocyclic Aramid Concentrated Solution

2010 ◽  
Vol 146-147 ◽  
pp. 470-474
Author(s):  
Lei Chen ◽  
Zu Ming Hu ◽  
Bao Shan Gao ◽  
Guo Ping Tang ◽  
Jun Rong Yu ◽  
...  
Keyword(s):  
Activation Energy ◽  
Molecular Weight ◽  
Flow Behavior ◽  
Viscosity Index ◽  
Solution Concentration ◽  
Structural Viscosity ◽  
Flow Activation Energy ◽  
Flow Activation ◽  
Concentrated Solution ◽  
Newtonian Behavior

By means of HAAKE RS105L cone and plate rheometer the rheological behavior of heterocyclic aramid concentrated solution, including viscous flow activation energy, non-Newtonian index, structural viscosity index of the heterocyclic aramid solution were studied. The effect of concentration and temperature of the solution and molecular weight of the polymer on its non-Newtonian behavior was investigated. The results showed that heterocyclic aramid concentrated solution prepared via low temperature condensation was non-Newtonian fluid. With the decrease of temperature, increase of solution concentration and heterocyclic aramid molecular weight, the deviation of the solution from Newtonian behavior decreased. The molecular weight of the polymer and the concentration of the solution affected the non-Newtonian behavior more intensively.

Effects of Reaction Temperature on Hydrocracking of Asphaltene over NiMo/γ-Al2O3

2011 ◽  
Vol 393-395 ◽  
pp. 1189-1192
Author(s):  
Ying Xian Zhao ◽  
Bo Shen
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Molecular Weight ◽  
Kinetic Equation ◽  
Apparent Activation Energy ◽  
Average Molecular Weight ◽  
Liquid Product ◽  
Order Kinetic ◽  
Increasing Temperature ◽  
Order Kinetic Equation

The hydrocracking of a pentane-insoluble asphaltene over NiMo/γ-Al2O3 at 623 - 703 K was investigated. The second order kinetic equation fits experimental data of asphaltene conversion adequately, giving the apparent activation energy to be 144 kJ/mol over the temperature range. Average molecular weight of liquid product was reduced significantly with increasing temperature.

Thermal Oligomerisation of Cardanol

e-Polymers ◽  
2006 ◽  
Vol 6 (1) ◽  
Author(s):  
Francisco Helder A. Rodrigues ◽  
José Roberto R. Souza ◽  
Francisco Célio F. França ◽  
Nágila M. P. S. Ricardo ◽  
Judith P. A. Feitosa
Keyword(s):  
Activation Energy ◽  
Double Bond ◽  
Average Molecular Weight ◽  
Hydrocarbon Chain ◽  
Relative Mass ◽  
Cashew Nut Shell Liquid ◽  
Flow Activation Energy ◽  
H Nmr ◽  
Cashew Nut ◽  
Flow Activation

AbstractCardanol was extracted from technical Cashew Nut Shell Liquid (CNSL), a naturally occurring meta-substituted long chain phenol and oligomerized by heating at 140 °C. Products were characterized by rheology, infrared and 1H NMR spectroscopy and thermogravimetric analysis (TGA). Increase in viscosity and the flow activation energy was found with increasing time of heating. The relative absorbance of double bond of the hydrocarbon chain decreased with time of heating and indicated that the oligomerization is taking place through the unsaturation of the side chain. Decrease in internal double bond as well as in vinyl bond, observed by 1H NMR, pointed out to the participation of these two kinds of unsaturation as well as monoene, diene and triene. The oligomerization is a slow process. With 40 h of heating, the average molecular weight increases only by 46%. Great differences were found in TGA curves of cardanol with different times of oligomerization. Thermal stability increases with time of heating. The degree of oligomerization could be determined from relative mass loss of the first event of TG, or from flow activation energy.

scholarly journals Extraction, Characterization, and Molecular Weight Determination ofSenna tora(L.) Seed Polysaccharide

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Harshal A. Pawar ◽  
K. G. Lalitha
Keyword(s):  
Molecular Weight ◽  
Intrinsic Viscosity ◽  
Flow Behavior ◽  
Average Molecular Weight ◽  
Flow Property ◽  
Stability Study ◽  
Angle Of Repose ◽  
Molecular Weight Determination ◽  
Pharmaceutical Excipient ◽  
Accelerated Stability

The objective of the present work was extraction of polysaccharide fromSenna toraL. seed and its characterization as a pharmaceutical excipient. Polysaccharide extraction was based on mechanical separation of the endosperm of seeds ofSenna tora, water dissolution, centrifugation, and precipitation with acetone. Standard procedures were used to study the viscosity, micromeritic properties, and microbial bioburden. Accelerated stability study was carried out on isolated polysaccharide for six months at 40°C/75 RH as per ICH guidelines. The gum obtained fromS. toraseeds was an amorphous free flowing odourless powder with dull brown colour (yield = 35% w/w). The bulk density, tapped density, and angle of repose data reveal thatS. toragum possesses good flow property. The intrinsic viscosity obtained was 1.568 dL/g. The average molecular weight of purifiedS. toragum was found to be 198 kDa by intrinsic viscosity method. The results indicated that viscosity of gum solution increases with increase in temperature. FTIR study revealed the absence of degradation or decomposition of polysaccharide at accelerated stability conditions for six months. It has been concluded that extracted polysaccharide can be used as pharmaceutical excipient in terms of flow behavior, microbial properties, and stability.

scholarly journals Rheological Behavior and Its Chemical Interpretation of Crumb Rubber Modified Asphalt Containing Warm-Mix Additives

2018 ◽  
Vol 2672 (28) ◽  
pp. 337-348 ◽  
Author(s):  
Haopeng Wang ◽  
Xueyan Liu ◽  
Panos Apostolidis ◽  
Tom Scarpas
Keyword(s):  
Activation Energy ◽  
Molecular Weight ◽  
Rheological Properties ◽  
Phase Angle ◽  
Complex Modulus ◽  
Crumb Rubber ◽  
Asphalt Binders ◽  
Flow Activation Energy ◽  
Modified Asphalt ◽  
Flow Activation

The microstructure and chemical composition of asphalt binders have a significant effect on their rheological properties and, therefore, their performance as road paving binders. This study aims to investigate the effects of warm-mix asphalt (WMA) additives, organic type and chemical type, on the rheological properties and chemical internal structure of base asphalt and crumb rubber modified asphalt (CRMA). A set of dynamic shear rheometer (DSR) tests was conducted to obtain the rheological parameters (e.g., complex viscosity, complex modulus, phase angle) of asphalt binders. The flow activation energy was calculated from Arrhenius equation based on viscosity data to rank the thermal susceptibility. Black diagrams and master curves of complex modulus and phase angle were utilized to analyze the rheological properties. The molecular weight distributions of asphalt binders were inverted from the phase angle master curve to evaluate the molecular weight characteristics. It was found that the the addition of crumb rubber into base asphalt improves the rheological properties of enhanced modulus and elasticity. Organic and chemical types of WMA additives have different chemo-physical effects on both base asphalt and CRMA. Phase angle inversion method provides a powerful tool to monitor the molecular structure change and, therefore, the chemo-physical interactions of asphalt binders induced by modifications. Finally, there is a good correlation between flow activation energy and molecular weight.

Influence of Chemical Nature on Flow Behavior of Polymers. I. Shear Rate and Temperature Dependence

1970 ◽  
Vol 43 (5) ◽  
pp. 1109-1115 ◽  
Author(s):  
E. A. Collins ◽  
T. Mass ◽  
W. H. Bauer
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Chemical Nature ◽  
Flow Behavior ◽  
Capillary Viscometer ◽  
Low Molecular Weight ◽  
Flow Activation Energy ◽  
Flow Activation ◽  
Made In ◽  
Low Shear

Abstract The flow behavior of low molecular weight liquid polybutadiene polymers was studied as a function of shear rate, temperature, and molecular structure. Measurements were made in the temperature range 15 to 50° C and shear rate range 1 to 15,000 sec−1 with a cone and plate and a capillary viscometer. Limiting low shear viscosity, flow activation energy, and critical shear rate marking onset of shear rate thinning were found to be strongly dependent upon the presence of functional groups such as hydroxyl, carboxyl, and nitrile. The modifying groups showed a greater effect than the molecular weight upon the properties measured.

Formation of Boundary Layer in the Flow of Shear-Dependent-Viscosity Fluids Between Parallel Plates

2017 ◽  
Author(s):  
Nariman Ashrafi ◽  
Ali Sadeghi ◽  
Mehdi Shafahi
Keyword(s):  
Boundary Layer ◽  
Flow Behavior ◽  
Vertical Wall ◽  
Shear Thickening ◽  
Finite Volume Scheme ◽  
Parallel Plates ◽  
Flow Behavior Index ◽  
Shear Dependent Viscosity ◽  
Shear Thickening Fluids ◽  
Dependent Viscosity

Formation of the boundary layer in the laminar flow of Herschel–Bulkley fluid between parallel plates is taken into consideration. In particular, the study is focused on the flow of the shear thinning and shear thickening fluids past a partial vertical wall in between the plates. Upon numerically solving the continuity and momentum equations the flow is analyzed throughout the domain using a finite volume scheme. The shear stress at the wall together with velocity distribution are evaluated and compared with experimental results for several values of Herschel-Bulkley coefficients for fluidity and flow behavior index.

scholarly journals Physicochemical Properties and Antioxidant Activity of Pumpkin Polysaccharide (Cucurbita moschata Duchesne ex Poiret) Modified by Subcritical Water

Foods ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 197
Author(s):  
Guoyong Yu ◽  
Jing Zhao ◽  
Yunlu Wei ◽  
Linlin Huang ◽  
Fei Li ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Antioxidant Activity ◽  
Molecular Mass Distribution ◽  
Subcritical Water ◽  
Flow Behavior ◽  
Average Molecular Weight ◽  
Great Influence ◽  
Cucurbita Moschata ◽  
Solution Treated ◽  
Linear Viscoelastic

In this paper, subcritical water (SCW) was applied to modify pumpkin (Cucurbita moschata Duchesne ex Poiret) polysaccharides, and the properties and antioxidant activity of pumpkin polysaccharides were investigated. SCW treatments at varying temperature led to changes in the rheological and emulsifying properties of pumpkin polysaccharides. SCW treatments efficiently degraded pumpkin polysaccharides and changed the molecular weight distribution. Decreases in intrinsic viscosity, viscosity-average molecular weight, and apparent viscosity were also observed, while the activation energy and flow behavior indices increased. The temperature of SCW treatment has a great influence on the linear viscoelastic properties and antioxidant activity of pumpkin polysaccharides. Pumpkin polysaccharides solution treated by SCW at 150 °C exhibited the highest emulsifying activity and antioxidant activity, which was probably due to a broader molecular mass distribution and more reducing ends exposed after treatment. Scanning electron microscopy showed that SCW treatment changed the microstructure of pumpkin polysaccharides, resulting in the exposure of bigger surface area. Our results suggest that SCW treatment is an effective approach to modify pumpkin polysaccharides to achieve improved solution properties and antioxidant activity.

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