Polybutadiene solubility parameter

As pointed out earlier, acrylics differ from the commonly used rubber precursors for PSA formulation in the fact that they often incorporate polar monomers, such as acrylic acid, A-vinyl pyrrolidone, vinyl acetate, or acrylamide. As a result, the solubility parameters of acrylic polymers are typically higher than those of rubbers, like polyisoprenes or polybutadienes. 

Influences of the different methacrylates and 1,2-polybutadiene as coagents on the mechanical and rheological properties of the peroxide-cured PP/EPDM TPVs were reported by Rishi and Noordermeer [39, 40]. They interpreted the results in terms of solubility parameter and cure kinetics. The effects of coagents on both processing and properties of the compound depend on the nature of the polymer, type of peroxide, and other compounding ingredients. Among the methacrylate... 

Table I lists the final results of solvent-swelling conditions which resulted in selecting 2,2,4-trimethylpentane and styrene at —25°C for a differential solvent pair. The table also includes the published values for the solubility parameters (a/CED) of the elastomers and the solvents. This table indicates that for the elastomer systems Cl-butyl-cts-polybutadiene or Cl-butyl-SBR excellent differentiation can be obtained.

The system Cl-buty 1-natural rubber (or cw-polyisoprene) could not be resolved by differential solvent techniques because the polymeric solubility parameters were too similar. At one end of the spectrum—i.e., with styrene at — 25 °C—natural rubber could be highly swollen while restricting the chlorobutyl swell, but the reverse was not possible, as indicated by the swelling volumes in the trimethylpentane. As displayed in Table II, attempts to use a highly symmetrically branched hydrocarbon with a very low solubility parameter, served only to reduce both the swelling of natural rubber and chlorobutyl. (Neopentane is a gas above 10°C and a solid below — 20°C). Therefore, for this report the use of differential solvents in the study of interfacial bonding in blends was limited to systems of Cl-butyl and cw-polybutadiene or SBR. 

As shown in Figures 5 and 7 the nature of the solvent does not appear to have any effect on T0 within experimental error. However, the solvent can have a profound influence on the morphology of cast block copolymer specimens. Thus, instead of the continuous polybutadiene phase normally observed, a continuous polystyrene phase appears to exist in Kraton 101 films cast from solution in MEK/THF mixtures (2). Methyl ethyl ketone has a solubility parameter of 9.3, only slightly higher than that of the solvents used in our work. It is clear from the data presented here that our films must have had continuous polybutadiene phases. 

The system with which we have begun our investigations is the styrene-dimethylsiloxane system. The dimethylsiloxane blocks should be considerably less compatible with polystyrene blocks than either polybutadiene or polyisoprene since the solubility parameter of dimethylsiloxane is much farther from that of polystyrene than are the solubility parameters of polybutadienes or of polyisoprenes (17), no matter what their microstructure. Furthermore, even hexamers of polystyrene and of polydimethylsiloxane are immiscible at room temperature and have an upper critical-solution temperature above 35°C (18). In addition, the microphases in this system can be observed without staining and with no ambiguity about the identity of the phases in the transmission electron microscope (TEM) silicon has a much higher atomic number than carbon or oxygen, making the polydimethylsiloxane microphases the dark phases in TEM (19,20). 

It is gratifying to see that the value of A for NR/PS given in Table I is in excellent agreement with 0.8 cal/cm3 which was estimated by Meier (4) for polybutadiene/PS from the solubility parameter difference. It is, however, doubtful that the present approach of using the equation-of-... 

Wettability of Elastomers and Copolymers. The wettability of elastomers (37, 38) in terms of critical surface tension was reported previously. The elastomers commonly used for the reinforcement of brittle polymers are polybutadiene, styrene-butadiene random and block copolymers, and butadiene-acrylonitrile rubber. Critical surface tensions for several typical elastomers are 31 dyne/cm. for "Diene rubber, 33 dyne/cm. for both GR-S1006 rubber and styrene-butadiene block copolymer (25 75) and 37 dyne/cm. for butadiene-acrylonitrile rubber, ( Paracril BJLT nitrile rubber). The copolymerization of butadiene with a relatively polar monomer—e.g., styrene or acrylonitrile—generally results in an increase in critical surface tension. The increase in polarity is also reflected in the increase in the solubility parameter (34,39, 40) and in the increase of glass temperature (40). We also noted a similar increase in critical surface tensions of styrene-acrylonitrile copolymers with the... 

Compatibility of polymers implies a semi-quantitative measure can be used to predict whether two or more polymers are compatible. The use of one of the semi-quantitative approaches, solubility parameter, was demonstrated by Hughes and Britt (22). It was concluded (8) that one parameter was insufficient to predict the compatibility. In this paper, we now introduce critical surface tension which is determined from the surface properties of a polymer. Though both of these parameters have been related by Gardon (15), we are inclined to use the latter because we can further describe the wettability between two polymers. For instance, by the use of yc, we can predict equally well that compatibility between polystyrene and polybutadiene can be improved if butadiene is... 

Volumetric coefficient of expansion in general. With subscripts C, M. PB, PS, P composite, matrix, polybutadiene, polystyrene, particle, respectively Mean distance between crazes in the volume With subscripts. A, B solubility parameter With subscripts. A, B, solubihty parameter... 

Problem 3.20 Calculate the solubility parameter for a methyl methacrylate-butadiene copolymer containing 25 mol % methyl methacrylate. The solubility parameter values for poly(methyl methacrylate) (PMMA) and polybutadiene (PB) homopolymers, calculated from molar attraction constants, are, respectively, 9.3 and 8.4 (cal cm ). ... 

Graft Copolymers. In graft copolymerization, a preformed polymer with residual double bonds or active hydrogens is either dispersed or dissolved in the monomer in the absence or presence of a solvent. On this backbone, the monomer is grafted in free-radical reaction. Impact polystyrene is made commercially in three steps first, solid polybutadiene rubber is cut and dispersed as small particles in styrene monomer. Secondly, bulk prepolymerization and thirdly, completion of the polymerization in either bulk or aqueous suspension is made. During the prepolymerization step, styrene starts to polymerize by itself forming droplets of polystyrene with phase separation. When equal phase volumes are attained, phase inversion occurs. The droplets of polystyrene become the continuous phase in which the rubber particles are dispersed. R. L. Kruse has determined the solubility parameter for the phase equilibrium. 

Figure 2. Calculation of solubility parameters from phase equilibrium data for the system styrenefl)/polystyrene(2)/polybutadiene(3)...

Note that Croucher and Hair (1980) have claimed that according to free volume theory, xiz is an order of magnitude smaller than that used by Feigin and Nappes (1978). It has subsequently been shown by Roe and Zin (1980), however, that the free volume contribution to xi3 is relatively unimportant. These authors obtained values of 23—014 for polystyrene and polybutadiene by experimental measurements of the miscibility of the two polymers, whereas the free volume contribution is only ca 0-01. Roe and Zin advocated the use of the solubility parameter approach to the calculation of j23. which is what has been adopted above. This is a further instance where the free volume theory proves inadequate at the quantitative level. This gross underestimation of X23 has unfortunately led Croucher and Hair (1980) to present erroneous values for the free energies of interaction for heterosterically stabilized systems. 

These concepts for formation of miscible blend of elastomers with similar or near equivalence of solubility parameters require the components to be similar in properties. Thus a wide variation in the properties of the elastomer blends by changing the relative amounts of the two elastomers is not typical since it is unlikely that, for example, a nonpolar polyolefin elastomer and a polar elastomer like acrylate would be similar in solubility parameters. This relative invariance in the properties of the blend compared to the components is an inherent limitation on the basic, economic, and technological need for elastomer blends, which is to generate new properties by blends of existing materials. Similar or near equivalence of solubility parameters can be difficult to predict from chemical structure. For example, chemically distinct 1,4-polyisoprene and 1,2-polybutadiene are miscible, but isomeric 1,2-polybutadiene and 1,4-polybutadiene are immiscible. It is illustrative of this concept that an apolar hydrocarbon elastomer and a highly polar elastomer such as an acrylate cannot have, under any practical structural manifestation for either, a similar solubility parameter and thus be miscible. 

Using the case of HiPS formation as an example, it can be seen from Table 3.1 that the solubility parameter of styrene is significantly closer to that of polystyrene than to that of polybutadiene. Predictably, then, styrene will swell the nascent polystyrene in preference to polybutadiene, and the locus of polymerization will center increasingly in the polystyrene phase as polymerization progresses. 

Figure 2. Swelling of cross-linked polybutadiene in solvents with varying solubility parameters. Solubility parameter has units of MPa. ...

Where the solubility parameter rule is in error is for natural rubber and polybutadiene. The differential in solubility parameters is around 0.6 but the two polymers are immiscible. Polybutadiene grade IISRP 1207 and an oil extended polymer such as IISRP 1712 have a differential of less than 0.1 and in this case the two elastomers are nearly fully miscible between the lower and upper critical solution temperatures. The blended elastomers mechanical properties then become a function of the filler type, distribution, vulcanization system, and any processing aids present. 

The Floiy-Huggins interaction parameter x for polybutadienes and EPDM with -heptane and solubility parameters 5 or c/s-PB, EPDM, and BNKS were reported in [20, 21],... 

Tables 3.1 (6) and 3.2 (6) present the solubility parameters of common solvents and polymers, respectively. These tables provide a quantitative basis for understanding why methanol or water does not dissolve polybutadiene or polystyrene. However, benzene and toluene are predicted to be good solvents...

Both carboxyl and amine liquid polymers have provided chemistries amenable to elastomer modification, with the polybutadiene—acrylonitrile copolymer providing solubility parameters close to if not equaling those of base epoxy resins. 

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