Steady Flow and Dynamic Viscosity of Branched Butadiene-Styrene Block Copolymers

1972 ◽  
Vol 45 (4) ◽  
pp. 1005-1014
Author(s):  
G. Kraus ◽  
F. E. Naylor ◽  
K. W. Rollmann
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Block Copolymers ◽  
Steady Flow ◽  
Domain Structure ◽  
Viscoelastic Behavior ◽  
Significant Degree ◽  
Two Phase ◽  
Total Molecular Weight ◽  
Block Structures

Abstract Steady flow and dynamic viscosities were determined for symmetrical linear and star-branched block copolymers of butadiene and styrene above their upper (polystyrene) glass transition. Block structures examined were B-S-B, (B-S-)3, S-B-S, (S-B-)3 and (S-B-)4. At constant molecular weight and total styrene content viscosities were greater for polymers terminating in styrene blocks, irrespective of branching. Branching decreased the viscosity of either polybutadiene-terminated or polystyrene-terminated block polymers, compared at equal Mw. However, comparisons at equal block lengths showed that the length of the terminal blocks, not the total molecular weight, governs the viscoelastic behavior of these polymers to a surprisingly good approximation. This unusual result is rationalized in terms of the two-phase domain structure of these polymers, which persists to a significant degree in the melt. Below the glass transition of the polystyrene blocks the effects of branching were masked by differences in the morphology of the domain structure unrelated to branching.

Viscoelastic Behavior of Styrene-Butadiene-Styrene Block Copolymers in Temperature Range of Glass-Rubber Transition of Styrene Block

1996 ◽  
Vol 69 (1) ◽  
pp. 73-80 ◽  
Author(s):  
N. Nakajima
Keyword(s):  
Molecular Weight ◽  
Block Copolymers ◽  
Viscoelastic Behavior ◽  
Shear Mode ◽  
Molecular Weight Polymer ◽  
Styrene Butadiene Styrene ◽  
The Difference ◽  
Tan Δ ◽  
Styrene Butadiene ◽  
Butadiene Styrene

Abstract Dynamic mechanical measurements were performed with styrene-butadiene-styrene (SBS) block copolymers, Kraton D-1101 and D-l 102. Isochronal data were obtained from −130 to 85°C in the tensile mode at 1 Hz and from 60 to 160°C in the shear mode at 1 rad/s. The isothermal measurements were also performed at 60, 90, 120, 140, and 160°C in the frequency range of 0.0316 to 100 rad/s. The results suggest that the two polymers have different morphologies although the styrene content and the diblock content are about the same for both polymers. Kraton D-1101, which has 1.5 times higher molecular weight, has 3–5 times higher rubbery modulus, compared to D-1102. The lower molecular weight polymer, D-1102, appears to have a larger amount of the mixed phase at the boundary. This is suggest by the lower temperature of the “domain disruption”, Tdd and the higher magnitude of tan δ at Tdd. This explains the difference in the rubbery moduli of the two polymers.

New Emulsion SBR Technology: Part I. Raw Polymer Study

2000 ◽  
Vol 73 (4) ◽  
pp. 731-742 ◽  
Author(s):  
Laurand Lewandowski ◽  
Morgan S. Sibbald ◽  
Ed Johnson ◽  
Michael P. Mallamaci
Keyword(s):  
Molecular Weight ◽  
World War Ii ◽  
High Molecular Weight ◽  
Viscoelastic Behavior ◽  
Flow Region ◽  
Size Exclusion ◽  
Styrene Butadiene Rubber ◽  
Butadiene Rubber ◽  
Two Phase ◽  
Styrene Butadiene

Abstract Emulsion styrene—butadiene rubber (ESBR) has been the workhorse of the tire industry since World War II. With the development of solution polymers, ESBR has seen a steady decrease in its use in tire applications. A novel ESBR has been developed which imparts some of the rheological behavior previously only observed in solution polymers. This new ESBR was prepared by blending a high molecular weight elastomer with a low molecular weight elastomer, each having a unique styrene-butadiene composition. A two-phase co-continuous morphology was observed by scanning probe microscopy when the bound styrene difference between the two components was greater than 18%, consistent with the two glass transition temperatures measured by thermal analysis. Blending also served to reduce the amount of very high molecular weight material (> 107 g/mol) readily observed in 1502- and 1712-type polymers by thermal field flow fractionation (ThFFF). ThFFF was found to be superior to size exclusion chromatography for fully characterizing the molecular weight and molecular weight distribution of the polymers. Time—temperature superposition was performed to characterize the viscoelastic behavior in the rubbery plateau and terminal zones. The ESBR blends showed a cross-over in the terminal flow region that was not observed in 1502- and 1712-type polymers.

scholarly journals Mechanical and Morphological Properties of Waterborne ABA Hard-Soft-Hard Block Copolymers Synthesized by Means of RAFT Miniemulsion Polymerization

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1259 ◽  
Author(s):  
Gordana Siljanovska Petreska ◽  
Arantxa Arbe ◽  
Clemens Auschra ◽  
Maria Paulis
Keyword(s):  
Molecular Weight ◽  
Block Copolymers ◽  
Film Formation ◽  
Miniemulsion Polymerization ◽  
Morphological Properties ◽  
Phase System ◽  
Two Phase ◽  
Raft Agent ◽  
Different Temperatures ◽  
Equilibrium Morphology

High molecular weight waterborne ABA block copolymers of styrene (St) and 2-ethylhexyl acrylate (2EHA) containing hard and soft domains were synthesized by means of RAFT (mini)emulsion polymerization using a bifunctional symmetric S,S-dibenzyl trithiocarbonate (DBTTC) RAFT agent. Miniemulsion polymerization was initially used for the synthesis of the A-block, which forms hard domains, followed by 2EHA pre-emulsion feeding to build the B-block soft domains. Polymerization kinetics and the evolution of the Molecular Weight Distribution (MWD) were followed during the synthesis of different ABA block copolymers. The thermal properties of the final symmetric block copolymers were studied on dried films by means of DSC. It was found that the block copolymers have two glass transitions, which indicates the presence of a two-phase system. Phase separation was investigated by means of microscopic techniques (AFM and TEM) and SAXS, both of the particles in the latex form, as well as after film formation at room temperature and after different post-treatments. Films were annealed at temperatures well above the glass transition temperature (Tg) of the hard phase to study the bulk morphology of the films after complete particle coalescence. Moreover, for comparison purposes, the films were re-dissolved in THF, and films were again cast directly from the homogeneous THF solutions. As THF is a good solvent for both blocks, such films serve as a reference for the equilibrium morphology. Finally, DMTA studies of the films annealed at different temperatures were performed to correlate the morphology changes with the mechanical properties of the block copolymers.

Structure-Property Relationships of Perfectly Alternating Polycarbonate-Polydimethylsiloxane Block Copolymers, Part II

1984 ◽  
Vol 57 (1) ◽  
pp. 184-202 ◽  
Author(s):  
S. H. Tang ◽  
E. A. Meinecke ◽  
J. S. Riffle ◽  
J. E. McGrath
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Block Copolymers ◽  
Dynamic Mechanical Properties ◽  
Block Length ◽  
Structure Property ◽  
Two Phase ◽  
K Value ◽  
Mechanical Coupling ◽  
Molecular Weights

Abstract The relationships between the properties and microstructures of two series of perfectly alternating bisphenol A-polycarbonate-polydimethylsiloxane block copolymers were studied. In the first series, the polycarbonate (PC) block length was kept constant while the block length of polydimethylsiloxane (PDMS) was varied. The tensile properties of these block copolymers were found to be a function of composition. Dynamic mechanical properties measured as a function of temperature revealed the two-phase nature of these materials. Transmission electron micrographs showed that all samples had a sponge-like morphology independent of composition. The rheological maximum viscosity for the sample containing PC and PDMS blocks of equal molecular weight and extrudate swells increased with PC content. Takayamagi's mechanical coupling model was used to predict the maximum loss tangent at the glass transition temperature of PDMS using the known properties of pure components. The predictions agreed fairly well with the experimental results. In a second series of block copolymers, the block molecular weights of both PC and PDMS were varied to keep the composition constant. The tensile strength of these samples was found to increase with block molecular weights, except for the sample having the highest block molecular weights. The lower tensile strength of this material was attributed to its lamellar type morphology. Cold crystallization of PDMS blocks was found for samples having high PDMS block molecular weight (greater than 8000 g/mole). The Tg of PC blocks followed the Fox-Flory equation with a higher K value than expected. The PDMS content in PC domains was calculated to range from 11% for material of low block molecular weights to about 1.3% for high block molecular weight material.

Ultimate Tensile Properties of Segmented Polyurethane Elastomers: Factors Leading to Reduced Properties for Polyurethanes Based on Nonpolar Soft Segments

1986 ◽  
Vol 59 (3) ◽  
pp. 405-431 ◽  
Author(s):  
T. A. Speckhard ◽  
S. L. Cooper
Keyword(s):  
Molecular Weight ◽  
Glass Transition ◽  
Phase Separation ◽  
Block Copolymers ◽  
Tensile Properties ◽  
Soft Segment ◽  
Low Molecular Weight ◽  
Polyurethane Elastomers ◽  
Soft Segments ◽  
Available Information

Abstract Factors that could explain the lower tensile properties of nonpolar soft-segment-based polyurethane block copolymers relative to those of conventional polyether or polyester polyurethanes have been examined. Many of the materials studied in the literature have suffered from the use of soft segments with poor functionality, which has led to low molecular weight, network defects, and an unfavorable amount of crosslinking. Additionally, most of the materials have been based on soft segments whose molecular weight appears to be too high to obtain optimum properties. Polyurethanes based on nonpolar soft segments are also likely to suffer from premature phase separation during polymerization leading to low molecular weight and compositional heterogeneity, especially if the reaction is done in bulk. The lower soft-segment glass-transition temperature of, in particular, the polydimethylsiloxane polyurethanes can also contribute to their lower tensile properties at room temperature. However, if differences in the soft-segment glass-transition temperatures are accounted for by comparing samples at equivalent values of T−Tg and other parameters are optimized, it appears that only a lack of soft-segment crystallizability under strain and possibly an excessively high degree of phase separation are inherently limiting the tensile properties of nonpolar soft-segment-based polyurethane block copolymers. The limited amount of available information concerning the effects of many of these factors suggests a need for additional work in this area.

Structural Characterization of Diene Block Copolymers by GPC and Ozonolysis—GPC Measurements

1987 ◽  
Vol 60 (1) ◽  
pp. 25-34 ◽  
Author(s):  
Yasuyuki Tanaka ◽  
Hisaya Sato ◽  
Junichi Adachi
Keyword(s):  
Molecular Weight ◽  
Chemical Composition ◽  
Block Copolymers ◽  
Block Structure ◽  
Triblock Copolymers ◽  
Thermoplastic Elastomer ◽  
Chemical Composition Distribution ◽  
Block Structures ◽  
Styrene Butadiene

Abstract The sequence distribution and block structure of styrene units in commercial styrene—butadiene and styrene-isoprene copolymers were analyzed by GPC measurements on the original copolymers and on ozonolysis products. Tapered-block structures are clearly differentiated by ozonolysis—GPC measurements. The content of large block styrene sequences in S-B-S type block copolymers was found to be 77 to 99% or more. S-B and S sequences in addition to the S-B-S sequence were observed for most of the triblock copolymers. A star-shaped S-B-S copolymer was distinguished from a linear copolymer by comparison of the molecular weight and chemical composition of the main and shoulder peaks by GPC and also by reference to the molecular weight of the block styrene sequence determined by ozonolysis—GPC measurements. A mixture of block copolymers was estimated for a high-styrene thermoplastic elastomer by GPC and ozonolysis—GPC measurements together with the measurement of chemical composition distribution. In a similar way the block structure was analyzed for S-I-S triblock copolymers.

The effect of methyl and methoxy substituents on dianilines for a thermosetting polyimide system

2020 ◽  
Vol 32 (7) ◽  
pp. 801-822 ◽  
Author(s):  
John J La Scala ◽  
Greg Yandek ◽  
Jason Lamb ◽  
Craig M Paquette ◽  
William S Eck ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Glass Transition ◽  
Elevated Temperature ◽  
Methyl Substituent ◽  
Glass Transition Temperatures ◽  
High Performing ◽  
Methoxy Substituent ◽  
Acidic Conditions ◽  
Thermal Stability Of

4,4′-Methylenedianiline (MDA) is widely used in high-temperature polyimide resins, including polymerization of monomer reactants-15. The toxicity of MDA significantly limits the manufacturability using this resin. Modifying the substitution and electronics of MDA could allow for the reduction of toxicity while maintaining the high-performing properties of the materials derived from the modified MDA. The addition of a single methyl substituent, methoxy substituent, location of these substituents, and location of the amine relative to the phenolic bridge were modified as were other non-aniline diamines. Various anilines were condensed with paraformaldehyde under acidic conditions to yield dianilines. These dianilines and diamines were reacted with nadic anhydride and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride in methanol to form the polyamic acid oligomers and heated at elevated temperature to form polyimide oligomers. It was found that the molecular weight of the oligomers derived from MDA alternatives was generally lower than that of MDA oligomers resulting in lower glass transition temperatures ( T gs) and degradation temperatures. Additionally, methoxy substituents further reduce the T g of the polymers versus methyl substituents and reduce the thermal stability of the resin. Methyl-substituted alternatives produced polyimides with similar T gs and degradation temperatures. The toxicity of the MDA alternatives was examined. Although a few were identified with reduced toxicities, the alternatives with properties similar to that of MDA also had high toxicities.

Phase Behavior in Aqueous Two-Phase Systems Containing Micelle-Forming Block Copolymers

1995 ◽  
Vol 28 (10) ◽  
pp. 3597-3603 ◽  
Author(s):  
Maarten Svensson ◽  
Per Linse ◽  
Folke Tjerneld
Keyword(s):  
Block Copolymers ◽  
Phase Behavior ◽  
Two Phase ◽  
Aqueous Two Phase Systems ◽  
Phase Systems
Sign in / Sign up

Export Citation Format

Share Document