Rheological Properties of Multichain Polybutadienes

1965 ◽  
Vol 38 (4) ◽  
pp. 893-906 ◽  
Author(s):  
Gerard Kraus ◽  
J. T. Gruver
Keyword(s):  
Molecular Weight ◽  
Branched Polymers ◽  
Linear Polymers ◽  
Newtonian Viscosity ◽  
Zero Shear Viscosity ◽  
Shear Rates ◽  
Molecular Weights ◽  
High Shear Rates ◽  
Long Chain ◽  
Newtonian Behavior

Abstract The introduction of one or two long chain branches into a polybutadiene molecule to form trichain or tetrachain molecules, respectively, leads to profound changes in Theological behavior. At low molecular weights the Newtonian (zero shear) viscosity is decreased relative to a linear polymer of the same molecular weight. At molecular weights exceeding 60,000 (trichain) or 100,000 (tetrachain), the Newtonian viscosity rises rapidly above the corresponding value for a linear polybutadiene. However, non-Newtonian behavior of the branched polymers becomes more pronounced the higher the molecular weights, so that at moderate to high shear rates the viscosity of the branched polymers is uniformly lower than that of linear polymers of identical molecular weight.

Synthesis and Dilute-Solution Behavior of Model Star-Branched Polymers

1978 ◽  
Vol 51 (3) ◽  
pp. 406-436 ◽  
Author(s):  
B. J. Bauer ◽  
L. J. Fetters
Keyword(s):  
Molecular Weight ◽  
Physical Properties ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Average Molecular Weight ◽  
Melt Processing ◽  
Branched Polymers ◽  
Linear Polymers ◽  
Dilute Solution ◽  
Long Chain

Abstract The occurrence of polymers branched in a random fashion is common. Chain transfer reactions can cause short- and long-chain branching in polymerizations such as the high-pressure polymerization of ethylene. Branching can also be introduced intentionally by the use of a polyfunctional monomer in end-linking polymerizations. Similar branching can be produced in addition polymerizations by the use of a small amount of difunctional monomer, e.g., divinylbenzene. There also has been much interest in graft polymerization by which long chain branches can be introduced onto a backbone, which is often a different polymer from the branches. The properties of branched polymers can be quite different from those of linear polymers of the same molecular weight. For example, bulk viscosities as well as concentrated and dilute solution viscosities can be lower for branched polymers than for a linear material of equivalent molecular weight. As an example, the melt processing behavior of polymers can be manipulated by alterations in the average molecular weight, molecular weight distribution, and the frequency and length of long branches in the molecules. Thus, there is an obvious need to correlate and characterize the type and degree of branching in a polymer with its effect on the physical properties in solution or melt. In all of the above examples of branching, there is a mixture of branched and unbranched material. The unbranched and branched polymers can have a wide molecular weight distribution, as can the branches themselves. Also, the frequency of branches and the segment lengths between branch points can vary. Hence, the physical properties of such materials represent an average of the properties of all the different species present.

Rheological Properties of Polybutadienes Prepared by n-Butyllithium Initiation

1965 ◽  
Vol 38 (4) ◽  
pp. 881-892
Author(s):  
J. T. Gruver ◽  
Gerard Kraus
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Flow Behavior ◽  
Average Molecular Weight ◽  
Polymer System ◽  
Newtonian Flow ◽  
Newtonian Viscosity ◽  
Long Chain Branching ◽  
Shear Rates ◽  
Molecular Weights

Abstract The flow behavior of n-butyllithium-polymerized polybutadienes was investigated as a function of molecular weight, temperature, and shear rate. At low shear rates these polymers exhibit Newtonian flow up to molecular weights of several hundred thousand so that “zero shear” Newtonian viscosities can readily be determined without the risk of long extrapolation. Above 10,000 molecular weight the Newtonian viscosities obey the well-known 3.4 power dependence on weight-average molecular weight. The entanglement spacing molecular weight is estimated at 5600. The temperature dependence of viscosity is substantially independent of molecular weight and shear stress and can be represented analytically by functions proposed in the literature. The apparent activation energy for viscous flow is not constant, but decreases with rising temperature. The flow of the polymers becomes increasingly non-Newtonian with the product of shear rate, molecular weight and Newtonian viscosity. However, the departure from Newtonian behavior is apparently less than for any polymer system whose flow behavior has been described in the literature. The indications are, therefore, that sharp molecular weight distribution and freedom from long chain branching favor Newtonian flow and that the n-butyllithium initiated polybutadienes represent some of the most perfectly linear, narrow distribution polymers known.

Flow curves of mixtures of acrylonitrile–styrene copolymers with different molecular weights at extremely high shear rates (abstract)

1991 ◽  
Vol 35 (4) ◽  
pp. 706-706
Author(s):  
Hideroh Takahashi ◽  
Yoshinori Inoue ◽  
Satoru Yamamoto ◽  
Osami Kamigaito
Keyword(s):  
High Shear ◽  
Flow Curves ◽  
Shear Rates ◽  
Molecular Weights ◽  
Styrene Copolymers ◽  
High Shear Rates

scholarly journals Rheological and Wetting Properties of Environmentally Acceptable Lubricants (EALs) for Application in Stern Tube Seals

Lubricants ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 100 ◽  
Author(s):  
F. Borras ◽  
Matthijn de Rooij ◽  
Dik Schipper
Keyword(s):  
Surface Tension ◽  
Shear Thinning ◽  
Mineral Oil ◽  
Experimental Techniques ◽  
High Shear ◽  
Shear Rates ◽  
Wetting Properties ◽  
High Shear Rates ◽  
Significant Difference ◽  
Newtonian Behavior

The use of Environmentally Acceptable Lubricants (EALs) for stern tube lubrication is increasing. Although the machine components of a sailing vessel are designed to operate together with mineral oil-based lubricants, these are being replaced by the less environmentally harmful EALs. Little is known about the rheological performance of EALs in particular at the high shear rates that occur in stern tube seals. In this study, the viscosity and wetting properties of a set of different EALs is analysed and compared to traditional mineral oil-based lubricants using a set of experimental techniques. Some of the EALs present Newtonian behavior whereas other show shear thinning. No significant difference in surface tension was observed between the different lubricants.

THE VISCOSITY – MOLECULAR WEIGHT RELATION FOR POLY-levo-2,3-BUTANEDIYL o-PHTHALATE

1948 ◽  
Vol 26b (12) ◽  
pp. 783-797
Author(s):  
R. W. Watson ◽  
N. H. Grace
Keyword(s):  
Molecular Weight ◽  
High Purity ◽  
Molecular Orientation ◽  
Degree Of Polymerization ◽  
Solution Viscosity ◽  
Dilute Solution ◽  
Molecular Weights ◽  
Complex Relation ◽  
End Group ◽  
Long Chain

The inherent viscosities of dilute solutions of acidic polyesters of high purity have been compared with number average molecular weights accurately determined by end-group titration. For unfractionated resins with a degree of polymerization from 2 to 11 [Formula: see text] the viscosity – molecular weight relation is linear in chloroform at 25 °C. Where [Formula: see text], K = 1.923 × 10−5 and β = 0.0176. For fractionated polyesters from DP 5 to 8, K = 1.959 × 10−6 and β = 0.0161. For unfractionated resins with a DP > 11, molecular weights increase more rapidly than inherent viscosities. Above [Formula: see text] for fractionated resins linearity is resumed, and the slope increases. Several attempts have been made to explain this complex relation. Apparently the short chains remain linear, and the formation of anisotropic fibers at a DP close to 100 establishes a degree of molecular orientation in the long-chain superpolyesters. Isomerization of levo-diol to the diastereoisomer during polycondensation is without effect on the dilute solution viscosity of the resulting resin. Preferential degradation of the longer chains is assumed to be partially responsible for the decreasing slope from DP 11 to 65. As yet it has not been possible to assess the roles played by changes in size distribution, and variation in solvation with increasing chain length, but the data point to a curved viscosity – molecular weight relation in chloroform at 25 °C.

Behavior of Rubber Hydrocarbon in a Molecular Still

1939 ◽  
Vol 12 (4) ◽  
pp. 789-793 ◽  
Author(s):  
W. Harold Smith ◽  
Henry J. Wing
Keyword(s):  
Molecular Weight ◽  
Vapor Pressure ◽  
High Molecular Weight ◽  
Molecular Species ◽  
Decomposition Temperature ◽  
Sedimentation Equilibrium ◽  
Chain Molecules ◽  
Molecular Weights ◽  
Average Value ◽  
Long Chain

Abstract Some investigators believe that rubber consists of associated molecules, and others accept Staudinger's view that long-chain molecules are formed by polymerization. Pummerer, Andriessen and Gündel have obtained a molecular weight as low as 600. Meyer and Mark believe that it is approximately 5,000, although they calculated on the basis of osmotic pressures values as high as 350,000. They, as well as Pummerer, consider that rubber is an associated colloid and that high molecular weights are caused by aggregates, sometimes called micelles. Staudinger, however, considers that the long-chain rubber molecule itself has a molecular weight of 200,000 or even 350,000, and that products with lower values, which may be formed in rubber, result from degradation. if the molecules are small it might be possible to distil them if their vapor pressure could be sufficiently increased, but none would distil without decomposition if the molecules are very large. Because the vapor pressure of rubber below its decomposition temperature is low, it appeared of interest to attempt to distil the material in a molecular still. Paraffin wax and sugar, both substances of relatively high molecular weight, have been successfully distilled in this type of apparatus. Subsequent to the work described in this paper, the molecular weight of sol rubber prepared at this Bureau was determined by Kraemer and Lansing of E. I. du Pont de Nemours & Co., Inc. They used the Svedberg method of sedimentation equilibrium in an ultracentrifuge with ethereal solutions of sol rubber. The temperature of the solutions during determinations was approximately 10° C, and an average value of 460,000 was obtained. There was evidenced of a mixture of molecular species.

scholarly journals Flow Curves of Mixtures of Acrylonitrile-Styrene Copolymers with Different Molecular Weights at Extremely High Shear Rates

1990 ◽  
Vol 18 (3) ◽  
pp. 125-128
Author(s):  
Hideroh TAKAHASHI ◽  
Yoshinori INOUE ◽  
Satoru YAMAMOTO ◽  
Osami KAMIGAITO
Keyword(s):  
High Shear ◽  
Flow Curves ◽  
Shear Rates ◽  
Molecular Weights ◽  
Styrene Copolymers ◽  
High Shear Rates

Rheological Properties of cis-Polybutadiene

1965 ◽  
Vol 38 (4) ◽  
pp. 907-920
Author(s):  
Gerard Kraus ◽  
J. T. Gruver
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Average Molecular Weight ◽  
Tensile Creep ◽  
Capillary Viscometer ◽  
Chain Branching ◽  
Long Chain Branching ◽  
Long Chain ◽  
Newtonian Behavior

Abstract The steady-state viscosity of a number of cis-polybutadienes was determined as a function of shear rate and temperature by use of a capillary rheometer. Polymers investigated differed in molecular weight distribution and long chain branching. None of the polymers exhibited Newtonian behavior, even at the lowest shear rates attainable. Nevertheless, for polymers of similar molecular weight distribution and minimum branching, all the capillary viscometer data could be reduced to a single curve by a reduced variable treatment. The molecular weight shift function was found to be the same as for polymers exhibiting a Newtonian flow range, i.e., a 3.4th power law in weight-average molecular weight. Broadening the molecular weight distribution or increasing the degree of long-chain branching led to increasingly pronounced non-Newtonian behavior. Tensile creep experiments showed nonlinear viscoelastic behavior for all polymers studied, even at small strains. This behavior was most pronounced in the more highly branched polymers. At very low stresses some of these polymers exhibited extremely high viscosities, the strain being almost completely recoverable. Under larger stresses the viscosity of these rubbers dropped several decades and in the capillary extrusion experiments these polymers flowed readily. This is the same behavior observed previously in high molecular weight branched (multichain) narrow distribution polybutadienes. It is tentatively explained by a constraint of the branch points on the slippage of chain entanglements. The fact that all cis-polybutadienes exhibit this behavior, while linear polybutadienes made by organolithium initiation do not, suggests that all cis-polybutadienes may be branched to some extent.

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