Polybutadiene domain

The use of lightly crosslinked polymers did result in hydrophilic surfaces (contact angle 50°, c-PI, 0.2 M PhTD). However, the surfaces displayed severe cracking after 5 days. Although qualitatively they appeared to remain hydrophilic, reliable contact angle measurements on these surfaces were impossible. Also, the use of a styrene-butadiene-styrene triblock copolymer thermoplastic elastomer did not show improved permanence of the hydrophilicity over other polydienes treated with PhTD. The block copolymer film was cast from toluene, and transmission electron microscopy showed that the continuous phase was the polybutadiene portion of the copolymer. Both polystyrene and polybutadiene domains are present at the surface. This would probably limit the maximum hydrophilicity obtainable since the RTD reagents are not expected to modify the polystyrene domains. 

Note An example is the incorporation of soft polybutadiene domains into glassy polystyrene to produce high-impact polystyrene. 

These ABA copolymers have an index of refraction of 1.5 and water absorption of about 0.2%. Unless hydrogenated to saturated block copolymers, these unsaturated unstabilized plastics are degraded in sunlight. The polybutadiene domains are attacked by aliphatic hydrocarbon solvents, such as hexane, and the polystyrene domains arc attacked by aromatic hydrocarbon... 

In spite of (Mw/Mn)s = 2.9, the morphology appears to be basically spherical, albeit with considerable connectivity of polybutadiene domains. Moreover, for this blend tan 8max = 0.028, T(tan 8max) = — 88 °C, with virtually no anisotropy in storage modulus, consistent with spherical or short rod-shaped polybutadiene domains. 

Craze Growth by Cavitation of Spherical Polybutadiene Domains 315... 

Schwier, C. E., Argon, A. S., and Cohen, R. E. (1985b) Crazing in polystyrene-polybutadiene di-block copolymers containing cylindrical polybutadiene domains, Poly-tner, 26, 1985-1993. 

Acrylonitrile is also commonly found in impact modifiers, such as the acrylonitrile-butadiene-styrene (ABS) type, produced by emulsion polymerisation. Polybutadiene seed latex particles are grafted onto styrene and acrylonitrile in a seeded emulsion polymerisation process. As the styrene-acrylonitrile copolymer shell forms, polybutadiene domains are spontaneously separated within. The resulting impact modifier particles are subsequently compounded with polystyrene to product high impact polystyrene (HIPS). The impact modification properties of the latex particles may be optimised through varying the butadiene content, the particle size and structure, and the shell molecular weight. A basic formulation for an ABS impact modifier is given in Table 6. 

In Figure 10, dynamic mechanical properties of random copolymer SBR 1011 (Ameripol 1011, BF Goodrich Rubber Co.) and block copolymer SBS (Kraton DllOl, Shell Chemicals Co.) are examined. SBR 1011 has only one tan 8 peak maximum temperature at —45°C due to its random structure however, Kraton DllOl has two tan 8 peak temperatures at -90°C and 100°C. The tan 8 peak at -90°C corresponds to polybutadiene domains (rubber domains) and the tan 8 peak at 100°C to polystyrene domains (end blocks) in the block copolymer. In the case of SBR random copolymer, the tan 8 peak temperature changes depending on the styrene concentration in the rubber. 

Figure 24 shows the viscoelastic properties of Kraton block copolymer blends with low-molecular-weight modifying resins. The rubber-resin compatibility data can be obtained from these curves. As mentioned in the previous section, a block copolymer can have two glass transition temperatures. A value at -90°C corresponds to polybutadiene domains (rubbery... 

High impact polystyrene (HIPS), where the presence of elastomeric polybutadiene domains provides toughening to polystyrene, is a material concept that has been successfully extended to engineering resins and other plastics. In this case, the addition of a toughening agent or impact modifier to the engineering resin is usually accomplished by melt blending. 

These rubbers contain crystalline particles of syndiotactic 1,2-polybutadiene in the matrix polymer of C2s-1,4-BR. The crystalline particle is composed of block copolymers of cis-1,4 butadiene/1,2-vinyl butadiene [34]. It has 80% crystallinity in the 1,2-polybutadiene domain and a melting point of 204 °C. The rubbers of VCR309, VCR412, and VCR617 have different amount of crystalline particles in the same matrix polymer. Although not shown in Table 6.5, VCR512 has a different matrix polymer that is more branched than the matrix polymer of other samples. 

---