Vector Styrenic block copolymer

Vector Styrene Block Copolymers, Dexco Polymers, A Dow/Exxon Partnership, Houston, Texas, 1997. 

Styrenic block copolymer (SBC) thermoplastic elastomers are produced by Shell Chemical (Kraton ), Firestone Synthetic Rubber and Latex, Division of Bridgestone/Firestone (Stereon t), Dexco Polymers (Vector ), EniChem Elastomers (Europrene ), and other companies. SBC properties and processes are described for these four producers TPEs. 

Vector SBS, SIS, and SB styrenic block copolymers are produced as diblock-free and diblock copolymers. The company s process to make linear SBCs yields virtually no diblock residuals. Residual styrene butadiene and styrene isoprene require endblocks at both ends of the polymer in order to have a load-bearing segment in the elastomeric network.2 However, diblocks are blended into the copolymer for certain applications. Vector SBCs are injection-molded, extruded, and... 

Styrene block copolymers are the most widely used TPEs. Styrenic TPEs are usually styrene butadiene styrene (SBS), styrene ethylene butadiene styrene (SEES), and styrene isoprene styrene (SIS). Styrenic TPEs usually have about 30 0 percent bound styrene. Principal styrenic TPE markets are molded shoe soles and other footwear, extruded film/sheet and wire/cable covering, and pressure-sensitive and hot-melt adhesives. They are also popular as grips for bike handles, kitchen utensils, clear medical products, and personal care products. Styrenic block copolymer thermoplastic elastomers are produced by Shell Chemical (Kraton), Firestone Synthetic Rubber and Latex, Division of Bridgestone/Firestone (Stereon), Dexco Polymers (Vector), EniChem Elastomers (Europrene), and other companies. 

Dexco (Exxon/Dow) has developed styrenic block copolymers as compatibilizers. to improve impact strength. Vector SBS (not containing halide salts) gives better heat stability than conventional block copolymers due to absence of residual halides, which can lead to property degradation. It can boost ultimate elongation and impact strength of PS waste. 

Linear low-density polyethylene (LLDPE) and PS resins were the same as described previously (Chapter 21). The various block copolymers that were used as compatibilizers have also been described (I). A series of crystalline copolymers (Q series) was prepared by hydrogenation of diblock and triblock copolymers of styrene and butadiene [styrene-hydrogenated butadiene (SEB) and styrene-hydrogenated butadiene—styrene (SEBS)J (1). Triblock copolymers of styrene and butadiene [styrene-butadiene-styrene (SBS)] and a noncrystalline hydrogenated block copolymer (SEBS) (Kraton) were supplied by Shell Chemical Co. Diblock copolymers of styrene and butadiene [styrene-butadiene (SB) (Vector)] were obtained from Dexco Polymers. The characteristics of the resins are given in Table I. 

Proprietary compatibilizers-cwm-impact modifiers offer a more economic solution and are widely used. These materials are formulated for specific types of polymer mixtures, viz. Blendex — polybutadiene-type compatibilizer for styren-ics, PVC, TPU, PET, EXL — an acrylic-based additive for PEST, Fusabond — maleated-PO compatibilizer for PO/PET blends, Vector — is SBS-type block copolymers with stabilizers, designed for PO/PS commingled mixtures, etc. 

Block copolymers containing 20-40% styrene are also useful as impact modifiers for ignition-resistant HIPS as well as other polystyrene resins. Kraton rubbers are available from Shell Chemical Co. and Vector rubbers are available from Dexco Polymers (a joint venture between The Dow Chemical Co. and The Exxon Chemical Co.). Both grades are used extensively for this purpose as are other similar products from other suppliers. Kraton rubbers are usually triblock copolymers of SBS type. The center block is polybutadiene with terminal blocks of polystyrene (49-51). By far the largest use of block copoljuners is in the form of TIPS resins. There are a number of suppliers, with Phillips Petroleum and BASF... 

Another approach to the orientation of exfoliated montmorillonite in polymers is the utilization of block copolymers. Work by Yung-Hoon Ha et al. [36] prepared oriented, montmorillonite nanocomposites in a styrene-butadiene-styrene (SBS) block copolymer (Vector 4461-D). Attempts to prepare exfoliated montmorillonite in block copolymers have been unsuccessful until the advent of this work. The montmorillonite was surface treated by two methods. 

Previous work by Ha and Thomas [37] provided the inspiration for the above work. The block copolymer for this work was polystyrene-isoprene-polystyrene (Vector 4411-D from Dexco Polymers) with a molecular weight of 18000 for the styrene blocks and 44000 for the... 

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