Styrene-butadiene rubber, ionomers

Polymers can be modified by the introduction of ionic groups [I]. The ionic polymers, also called ionomers, offer great potential in a variety of applications. Ionic rubbers are mostly prepared by metal ion neutralization of acid functionalized rubbers, such as carboxylated styrene-butadiene rubber, carboxylated polybutadiene rubber, and carboxylated nitrile rubber 12-5]. Ionic rubbers under ambient conditions show moderate to high tensile and tear strength and high elongation. The ionic crosslinks are thermolabile and, thus, the materials can be processed just as thermoplastics are processed [6]. 

Orientations in elongated mbbers are sometimes regular to the extent that there is local crystallization of individual chain segments (e.g., in natural rubber). X-ray diffraction patterns of such samples are very similar to those obtained from stretched fibers. The following synthetic polymers are of technical relevance as mbbers poly(acrylic ester)s, polybutadienes, polyisoprenes, polychloroprenes, butadiene/styrene copolymers, styrene/butadiene/styrene tri-block-copolymers (also hydrogenated), butadiene/acrylonitrile copolymers (also hydrogenated), ethylene/propylene co- and terpolymers (with non-conjugated dienes (e.g., ethylidene norbomene)), ethylene/vinyl acetate copolymers, ethyl-ene/methacrylic acid copolymers (ionomers), polyisobutylene (and copolymers with isoprene), chlorinated polyethylenes, chlorosulfonated polyethylenes, polyurethanes, silicones, poly(fluoro alkylene)s, poly(alkylene sulfide)s. 

Weiss et al. [75] have synthesized Na and Zn salt of sulfonated styrene(ethylene-co-butylene)-styrene triblock ionomer. The starting material is a hydrogenated triblock copolymer of styrene and butadiene with a rubber mid-block and PS end-blocks. After hydrogenation, the mid-block is converted to a random copolymer of ethylene and butylene. Ethyl sulfonate is used to sulfonate the block copolymer in 1,2-dichloroethane solution at 50°C using the procedure developed by Makowski et al. [76]. The sulfonic acid form of the functionalized polymer is recovered by steam stripping. The neutralization reaction is carried out in toluene-methanol solution using the appropriate metal hydroxide or acetate. 

The microphase structure and mechanical properties of the blends containing neat acrylonitrile-butadiene-styrene copolymer (ABS), styrene-acrylonitrile copolymer (SAN) and sodium sulfonated SAN ionomer have been investigated as a function of ion content of the ionomer in the blend by Park et a/.51 The interfacial adhesion was quantified by H NMR solid echo experiments. The amount of interphase for the blend containing the SAN ionomer with low ion content (3.1 mol%) was nearly the same as that of ABS, but it decreases with the ion content of the ionomer for the blend with an ion content greater than 3.1 mol%. Changing the ionomer content in the blends shows a positive deviation from the rule of mixtures in tensile properties of the blends containing the SAN ionomer with low ion content. This seems to result from the enhanced tensile properties of the SAN ionomer, interfacial adhesion between the rubber and matrix, and the stress concentration effect of the secondary particles. 

N nylon, PO polyolefin, elastomer, TPU thermoplastic urethane, GF glass fiber, NBR nitrile rubber, MAH maleic anhydride, EPR ethylene-propylene copolymer, l ionomer, M- mineral, ABS acrylonitrile-butadiene-styrene copolymer, PPE poly (phenylene ether), R reinforcement, PTFE poly(tetrafluoroethylene), CF° carbon fiber, PEBA poly(etherblockamide), S silicone, RIPP D reaction injection molding plastic, and ASA acrylate-styrene-acrylonitrile copolymer. 

---