Microstructures of Polybutadienes and Butadiene-Styrene Copolymers

1955 ◽  
Vol 28 (1) ◽  
pp. 121-130
Author(s):  
John L. Binder
Keyword(s):  
Alkali Metal ◽  
Physical Properties ◽  
Metal Catalysts ◽  
Maximum Amount ◽  
Styrene Copolymers ◽  
Emulsion Systems ◽  
Emulsion Polymerizations ◽  
Increasing Temperature ◽  
Butadiene Styrene

Abstract Polybutadienes and butadiene-styrene copolymers were prepared to study the effect of recipe variables on the physical properties and to learn whether there are correlations between the microstructures and physical properties. The changes in the microstructure of emulsion polybutadienes and butadiene-styrene copolymers of the types studied, which can be produced by either recipe variables or changes in temperature, are limited. The maximum amount of cis-1,4-addition amounted to 23 per cent (in the butadiene part of butadienestyrene copolymers) at 100° C, the maximum amount of trans-1,4- was about 80 per cent at −35° C, and the maximum amount of 1,2-addition was about 20 per cent. While the amount of cis-1,4-addition increases with increasing temperature, it is unlikely that polymers containing even 50 per cent cis-1,4-addition can be made at practical temperatures in emulsion systems. The structures of polybutadienes may be changed markedly by alkali-metal catalysts. The structure is affected by the kind of catalyst, by the temperature, and by promotors. Emulsion polymerizations are not likely to yield improved polymers for practical uses, but much can be done to tailor polymers for specific uses by using alkali-metal catalysts in bulk or solution systems.

Properties of Random and Block Copolymers of Butadiene and Styrene. III. Three Sequence Styrene-Butadiene-Styrene Block Polymers

1967 ◽  
Vol 40 (4) ◽  
pp. 1183-1199 ◽  
Author(s):  
C. W. Childers ◽  
G. Kraus
Keyword(s):  
Tensile Strength ◽  
Block Copolymers ◽  
Polymer Chains ◽  
Two Phase ◽  
Styrene Copolymers ◽  
Relaxation Measurements ◽  
Styrene Butadiene Styrene ◽  
Increasing Temperature ◽  
Styrene Butadiene ◽  
Butadiene Styrene

Abstract In butadiene styrene copolymers containing long block sequences chain segments associate with like segments to form a two phase structure. Properties of such polymers are dependent not only on composition and molecular weight but also on block sequence along the chain. Polymers containing two or more polystyrene blocks per molecule form networks and exhibit elastomeric properties in the uncured state resembling those of filler reinforced vulcanizates. This behavior is shown both by linear styrene-butadiene-styrene elastomers and multichain block copolymers branched in the polybutadiene blocks. A prominent loss tangent peak was observed around —40° C for the multichain polymers. Stress strain following prestretching and stress relaxation measurements indicate some shifting of polystyrene associations during stretching. Tensile strength is reduced by increasing temperature and addition of plasticizers. Reinforcement by polystyrene domains in vulcanized block copolymers is evident from tensile strength, dynamic modulus, and swelling measurements, but decreases with increased crosslinking. The number of styrene sequences in the primary molecules is less important after vulcanization as crosslinking destroys the individuality of the original polymer chains.

Structure of Alkali Metal-Catalyzed Butadiene Polymers

1953 ◽  
Vol 26 (3) ◽  
pp. 522-527
Author(s):  
A. W. Meyer ◽  
R. R. Hampton ◽  
J. A. Davison
Keyword(s):  
Transition Temperature ◽  
Alkali Metal ◽  
Infrared Absorption ◽  
Styrene Copolymers ◽  
A Value ◽  
Second Order Transition ◽  
Metal Catalyzed ◽  
Sodium And Potassium ◽  
Absorption Measurements ◽  
Butadiene Styrene

Abstract The structures of various sodium and potassium-catalyzed butadiene polymers were determined from infrared absorption measurements. All of the polymers had a higher proportion of butadiene in the 1,2-configuration (45–80 per cent) than emulsion polybutadiene (18–23 per cent). Polybutadienes catalyzed by potassium had 15–20 per cent less butadiene in the 1,2-configuration than those in which sodium was the catalyst. When a mixture of sodium and potassium was used, the results were nearly the same as with the potassium catalyst alone. Polybutadienes made at 5° had 10 to 15 per cent more butadiene in the 1,2-configuration than those made at 45°. Diluent type had little or no effect on the structure of the polybutadienes. The butadiene portions of butadiene-styrene copolymers were found to have the same relative proportions of 1,2-, cis-1,4- and trans-1,4-configurations as the butadiene homopolymers. The second order transition temperature of sodium-catalyzed polybutadiene polymerized at 30° was −45°, whereas the 75° polybutadiene had a value of −64°.

Molecular Weight Distribution of Polystyrene and of Butadiene-Styrene Copolymers Prepared in Emulsion Systems

1970 ◽  
Vol 43 (6) ◽  
pp. 1424-1438
Author(s):  
C. A. Uraneck ◽  
J. E. Burleigh
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Homologous Series ◽  
Degree Of Branching ◽  
Styrene Copolymers ◽  
Divinyl Benzene ◽  
Emulsion Systems ◽  
Molecular Weight Fractions ◽  
Butadiene Styrene

Abstract Polystyrene and butadiene—styrene copolymers (SBR) were parepared in emulsion systems with a homologous series of commercial mercaptan modifiers. The molecular weight distribution (MWD) of the sets of polymers changed in a consistant manner when the regulating index of the mercaptan was relatively low. However the shape of the MWD curves appeared distorted in comparison to theoretical curves when the modifier depleted rapidly and when divinyl-benzene was present in the system. The divergence from the theoretical curve is attributed to a higher degree of branching in the high molecular weight fractions. Differences in MWD of SBR made with n- and tert-dodecyl mercaptans was marked. Notable differences were also found for SBR 1500 samples from the industry at random, but only slight differences were seen in a set of SBR 1503 samples. This study shows how the MWD of polymers prepared in emulsions can be varied simply by use of modifiers with different regulating indexes.

X-Ray Studies of Low-Temperature Polybutadiene and Butadiene-Styrene Copolymers

1949 ◽  
Vol 22 (2) ◽  
pp. 356-369 ◽  
Author(s):  
Karl E. Beu ◽  
W. B. Reynolds ◽  
C. F. Fryling ◽  
H. L. McMurry
Keyword(s):  
Molecular Weight ◽  
Low Temperature ◽  
Polymer Chains ◽  
Polymerization Temperature ◽  
X Ray ◽  
Styrene Copolymers ◽  
Emulsion Polymerizations ◽  
Diffraction Patterns ◽  
Ray Patterns ◽  
Butadiene Styrene

Abstract Although it is now generally recognized that the temperature of polymerization affects profoundly the properties of emulsion elastomers, there is very little evidence available pertaining to the cause of the variations of properties. It is felt by some that the improved properties of low-temperature elastomers can be related to variations in molecular weight and molecular-weight distribution. In this laboratory, however, the opinion has prevailed that the lower emulsion polymerization temperatures appreciably alter the fine structure of the molecules with an increase in the regularity of the polymer chains. If there were actually less branching and cross-linking in low-temperature polymers, and less 1,2-addition to monomer components, the increased order should be evident from x-ray diffraction patterns. To provide information on the above questions, x-ray studies were made with four purposes in view: (1) to determine the effect of polymerization temperature on the crystallization properties of unstretched and stretched polybutadienes; (2) to determine the influence of styrene content on the crystallization of butadiene-styrene copolymers; (3) to study some effects of compounding and vulcanization on crystallizable polybutadiene; and (4) to use the preferred orientation patterns obtained from some of these polymers for structural evaluations. To accomplish these objectives, x-ray patterns were obtained at several temperatures of some unstretched and stretched polybutadiene polymers, butadiene-styrene copolymers, and a vulcanized and compounded polybutadiene. The polybutadienes were prepared by emulsion polymerizations at 55°, 40°, 30°, 20°, 5°, −10° and −20° C. Since the −20° C polybutadiene showed the most marked crystallization patterns, the effects of compounding and of styrene addition were studied, using polymers prepared at this temperature for comparison. Three butadiene-styrene copolymers containing, respectively, 10, 20, and 30 per cent styrene in the monomer charge and one vulcanized polybutadiene compounded with Wyex carbon black were studied.

Effect of Temperature on Ozone Cracking of Rubbers

1966 ◽  
Vol 39 (3) ◽  
pp. 643-650
Author(s):  
A. N. Gent ◽  
J. E. McGrath
Keyword(s):  
Polymer Chains ◽  
Effect Of Temperature ◽  
Ozone Molecule ◽  
Segmental Mobility ◽  
Network Chain ◽  
Styrene Copolymers ◽  
Rates Of Growth ◽  
Rate Controlling Step ◽  
Limiting Value ◽  
Butadiene Styrene

Abstract The rates of growth of single ozone cracks have been measured for vulcanizates of a series of butadiene—styrene copolymers, over a temperature range from − 5° C to 95° C. The rates appear to be determined by two mechanisms. At low temperatures, near the glass transition temperature, they are quantitatively related to the segmental mobility of the polymer. The principal rate-controlling step in this case is concluded to be movement of the polymer chains after scission to yield new surface. At high temperatures the rate approaches a limiting value of 10−3 cm/sec/mg of ozone/1. This is about 1/1000 of the maximum possible value when instantaneous reaction of one incident ozone molecule causes scission of one network chain.

ChemInform Abstract: Syntheses, Structures, Physical Properties, and Electronic Properties of Some AMUQ3Compounds (A: Alkali Metal, M: Cu or Ag, Q: S or Se).

ChemInform ◽  
2008 ◽  
Vol 39 (45) ◽  
Author(s):  
Jiyong Yao ◽  
Daniel M. Wells ◽  
George H. Chan ◽  
Hui-Yi Zeng ◽  
Donald E. Ellis ◽  
...  
Keyword(s):  
Alkali Metal ◽  
Physical Properties ◽  
Electronic Properties
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