S-block- copolymer

Af for poly(ethylene- (9-butylene) is similar to that of poly(ethylene-i (9-prop5lene) (42). Because of these differences in S—I—S block copolymers are... 

The S—EB—S block copolymers produced in this way have excellent resistance to degradation (49). Similarly, S—I—S block copolymers can be hydrogenated to give the more stable S—EP—S equivalents. 

Matson M.W. and Bates E.S., Block copolymer microstructures in the intermediate-segregation regime, J. Chem. Phys., 106, 2436, 1997. 

Bates E.S. and Eredricson E.S., Block copolymer thermodynamics Theory and Experiment, Ann. Rev. Phys. Chem., 41, 525, 1990. 

Sauter mean diameter, 11 795, 13 135, 23 186, 188, 189, 190-191 Sauter mean drop diameter, 10 755, 756 Savannah River production reactors, 17 583 Savard/Lee gas-shielded tuyere, 16 151 Savard-Lee injectors, 14 741 Savory, 23 171 Saybolt color scale, 7 310 Saybolt Universal Seconds (SUS), 15 207 Saytex HP-7010, 11 474 S-B-S block copolymers, 24 706 S-B-S polymers, 24 713-714, 715 SC9... 

Shrink-resist science/technology development of, 26 391 Shrink-resist treatments, 26 391-393 additive, 26 393 chlorine-based, 26 392 chlorine-free, 26 392-393 Shuiskite, 6 471t Shutdown period, 29 494 Shutdown systems, 20 671-672 Shuttle vectors, 26 482-483 Sialon-bonded silicon carbide, 22 541 Siberian red lead, 6 468 S-iB-S block copolymers, 24 707 SiC-ceramic, 22 525. See also Silicon carbide... 

S-I-S block copolymers, 24 706, 707 Si-Si02 interface, 9 731-732 S-I-S junctions, V-I characteristics of,... 

Substitute for Conventional Vulcanized Rubbers, For this application, the products are processed by techniques and equipment developed for conventional thermoplastics, ie, injection molding, extrusion, etc. The S—B—S and S—EB—S polymers are preferred (small amounts of S—EP—S are also used). To obtain a satisfactory balance of properties, they must be compounded with oils, fillers, or other polymers compounding reduces costs. Compounding ingredients and their effects on properties are given in Table 8. Oils with high aromatic content should be avoided because they plasticize the polystyrene domains. Polystyrene is often used as an ingredient in S—B—S-based compounds it makes the products harder and improves their processibility. In S—EB—S-based compounds, crystalline polyolefins such as polypropylene and polyethylene are preferred. Some work has been reported on blends of liquid polysiloxanes with S—EB—S block copolymers. The products are primarily intended for medical and pharmaceutical-type applications and hardnesses as low as 5 on the Shore A scale have been reported (53). 

Unpublished work at BASF has shown that using these S-EB-S block copolymers the highest notched impact strength is obtained with a high molecular weight product. Thus for the S-EB-S block copolymers of the Kraton... 

Figure 19.8 TEM image of sPS modified with S-EB-S block copolymer...

The use of olefin rubbers [18] as good impact modifiers for sPS when used in conjunction with S-B or S-B-S block copolymers, which may be hydrogenated in the butadiene phase, has also been described. Instead of butadiene, isoprene can be used. Examples of the olefinic polymers are polyethylene, ethylene-propylene rubbers (EPR) and polypropylene-(ethylene propylene rubber) block copolymers. Here the styrene block copolymers presumably function as... 

Figure 19.10 TEM images of rubber-modified sPS with craze tips along imaginary lines (---), presumably lamellae. Rubber modification 35 % S-EB-S block copolymer...

It would appear that these rubbers have a similar toughening effect as the S-EB-S block copolymers. However, a synergistic effect is present when a mixture of both impact modifiers is employed [27]. 

Figure 25.16 TEM of S/DPE modified with a S-BH-S block copolymer (a) S/DPE(15) matrix (b) S/DPE(30) matrix...

As stated earlier, S/DPE copolymers are compatible with GPPS up to a DPE content of about 15wt%. This means that on modifying S/DPE(>15) with S-B(H)-S the impact modification decreases owing to decreased compatibility between the S/DPE matrix and the styrene blocks of the S-B(h>-S impact modifier. S-DPE, however, is prepared anionically and using this polymerization mechanism S/DPE-butadiene S/DPE block copolymers can be prepared. Thus the S/DPE blocks can be tailor-made to be compatible with the S/DPE polymer matrix. For compatibility, the DPE content of the blocks and the matrix should not differ by more than about 15 %. As with the S-B(H)-S block copolymers, the double bonds of the butadiene phase should be removed by hydrogenation. 

Dutta BK and Sikdar SK. Separation of volatile organic compounds from aqueous solutions by pervaporation using S-B-S block copolymer membranes. Env. Sci. Tech. 1999 33(10) 1709-1716. 

S-EB-S block copolymers have a saturated midblock and so can be compounded with suitable resins and oils to make adhesives and sealants that have improved stability during long-term or extreme temperature exposure. In addition, hot-melt adhesives formulated from these polymers are more stable under melt processing conditions and can be applied at high temperatures. Nitrogen-blanketing is not required. Stable adhesives and sealants with large amounts of oils and resins can be formulated from these polymers. 

The silicone semi-lPNs consist of mixing a hydride-containing silicone prepolymer and a vinyl functionalized silicone polymer into a thermoplastic matrix such as PA, PBT, thermoplastic polyurethane (TPU) or styrene-ethylene/butylene-styrene (S-EB-S) block copolymer elastomer. The two silicone prepolymers co-react in the thermoplastic matrix during melt extrusion and injection molding to form a partially crosslinked network within the thermoplastic matrix. 

In commercial thermoplastic S-B-S rubber, the end-block phase is present in a smaller proportion with a styrene-to-butadiene (end-block-to-midblock) ratio in the range 15 85 to 40 60 on weight basis. The useful temperature range of S-B-S copolymer lies between the Tg of polybutadiene and polystyrene. Below the Tg of polybutadiene, the elastomeric midblocks become hard and brittle. Above the Tg of polystyrene, the domains soften and cease to act as cross-links for the soft midblocks. Between the Tg of both homopolymers, however, the hard styrene domains prevent the flow of the soft elastomeric butadiene midsegments through a network similar to vulcanized rubber. Therefore, within normal use temperature, S-B-S block copolymer retains the thermoplasticity of styrene blocks and the toughness and resilience of the elastomer units. 

---