Polybutadiene physical properties

Among the techniques employed to estimate the average molecular weight distribution of polymers are end-group analysis, dilute solution viscosity, reduction in vapor pressure, ebuUiometry, cryoscopy, vapor pressure osmometry, fractionation, hplc, phase distribution chromatography, field flow fractionation, and gel-permeation chromatography (gpc). For routine analysis of SBR polymers, gpc is widely accepted. Table 1 lists a number of physical properties of SBR (random) compared to natural mbber, solution polybutadiene, and SB block copolymer. 

The Ekestone group also polymerized 1,3-butadiene to give an extremely high mol wt polybutadiene of 70% cis-1 4 stmcture. In thek research, they purposefully avoided the preparation of vinyl stmctures in both polyisoprene and polybutadiene since it was beheved that vinyl groups adversely affected tke performance. Since natural mbber was 99.9% cis-1 4 stmcture and had superior properties, they beheved that a 1,4 stmcture was necessary for acceptable physical properties. The addition of polar compounds to the hthium-catalyzed polymerization of butadiene changes the microstmcture from the 90% tij -l,4 stmcture to a mixed cis-1 4 and trans-1 4 microstmcture. 

The physical properties of low melting point (60—105°C) syndiotactic polybutadienes commercially available from JSR are shown in Table 1. The modulus, tensile strength, hardness, and impact strength all increase with melting point. These properties are typical of the polymer made with a cobalt catalyst modified with triphenylphosphine ligand. 

Table 1. Physical Properties of Low Melting Syndiotactic 1,2-Polybutadiene...

Fig. 5. Effect of 1,2-polybutadiene level on tine physical properties.

The physical properties of polystyrene depend upon the specific reaction components, the mass ratios of the components, and the conditions at which the reaction occurs. These will be discussed later. The impurities remaining in the polystyrene also affect the properties. For instance, the heat distortion temperature may be as low as 70°C if there is unreacted styrene present. It is normally between 90 and 95°C. Therefore the maximum percentage of styrene that will be allowed in the product is 0.01%. Careful drying is also necessary if the polystyrene is to be extruded. For this application the polystyrene must contain a maximum of 0.03-0.05% water. We will set 0.03% as the maximum amount of water allowed. The specifications for the polystyrene are given in Table 3E-1. Different types of rubbers may be used for making impact polystyrenes.12 We shall use polybutadiene. 

Polybutadiene (PB), 9 558 14 246 24 703 commercial block copolymers, 7 648t oxygen permeability at 25°C, 3 400 physical properties of, 4 376t in rubber compounding, 21 764-765 synthesis, 4 375-377 in tire compounding, 21 807 nel-Polybutadiene, 7 610t Polybutadiene-based urethane sealants, 22 36... 

The information on physical properties of radiation cross-linking of polybutadiene rubber and butadiene copolymers was obtained in a fashion similar to that for NR, namely, by stress-strain measurements. From Table 5.6, it is evident that the dose required for a full cure of these elastomers is lower than that for natural rubber. The addition of prorads allows further reduction of the cure dose with the actual value depending on the microstructure and macrostructure of the polymer and also on the type and concentration of the compounding ingredients, such as oils, processing aids, and antioxidants in the compound. For example, solution-polymerized polybutadiene rubber usually requires lower doses than emulsion-polymerized rubber because it contains smaller amount of impurities than the latter. Since the yield of scission G(S) is relatively small, particularly when oxygen is excluded, tensile... 

With only small differences in (Is)max the choice of the binder system is influenced by processability, physical properties, and propellant density. Thus, with the polyether binder an Is of 247 is reached with about 14% binder, but with the polyester the same Is is obtained with 11.5% binder, which is a definite disadvantage in terms of processability and mechanical properties. The higher Is with the polybutadiene binder is realized only at high solids loadings, but owing to its lower density, processability is still satisfactory. 

Anionic polymerization has also been used to make telechelic polymers (Greek telos, end, and chele, claw), i.e., polymers with reactive terminal groups.We coined the term, telechelic in 1957 and it has been accepted ever since in technical as well as patent literature. Liquid carboxy- and hydroxy telechelic polybutadienes initiated with difunctional organolithium initiators are commercially produced since 1962. Some of the physical properties,production details and uses as in solid rockets... 

Haley (Ref 86) reported on the effect of gamma radiation in the chemical and physical properties of TP-H-8009 propint which consisted of AP/polybutadiene-acrylic acid/Al. This Minuteman propint is stable up to 2.5 x 107 R. In this dose range, no significant losses were observed. However, beyond this range, the proplnt was unable to survive the initial pressure buildup in a rocket engine consequently ballistic failure occurred... 

Most ABS is made by emulsion polymerization. A polybutadiene or nitrile rubber latex is prepared, and styrene plus acrylonitrile are grafted upon the elastomer in emulsion. The effect of rubber particle size in ABS graft copolymer on physical properties is the subject Chapter 22 by C. F. Parsons and E. L. Suck. Methyl methacrylate was substituted for acrylonitrile in ABS by R. D. Deanin and co-workers. They found a better thermoprocessability, lighter color, and better ultraviolet light stability. 

Another widely used copolymer is high impact polystyrene (PS-HI), which is formed by grafting polystyrene to polybutadiene. Again, if styrene and butadiene are randomly copolymerized, the resulting material is an elastomer called styrene-butadiene-rubber (SBR). Another classic example of copolymerization is the terpolymer acrylonitrile-butadiene-styrene (ABS). Polymer blends belong to another family of polymeric materials which are made by mixing or blending two or more polymers to enhance the physical properties of each individual component. Common polymer blends include PP-PC, PVC-ABS, PE-PTFE and PC-ABS. 

Early in the development of solid propellant, the asphalt composites were found to have poor physical properties, such as cracking under normal temperature cycling, poor tensile characteristics, etc. They were replaced with the elastomeric polymers which have become the present-day binders. The first of these was Thiokol rubber, a polysulfide rubber, whichgives the propellant with good physical properties. The presence of the sulfur atom in the Thiokol rubber decreases the performance compared to a CHO polymer thus the most frequently used binders are polyurethane, polybutadiene acrylic acid (PBAA), epoxy resin, etc. The choice of the latter binders is made with regard to physical properties rather than performance. 

TABLE 1. Physical properties of derivatized polybutadiene diol containing a acrylic acid termini. 

TABLE 2. Physical properties of l,4-cis-poly(polybutadiene-co-urethane) prepared at 70°C using the stoichometry described in Table 1. 

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