Kraton copolymers melts

Thermoplastic rubber block copolymers, with completely new adhesive performance, were developed in 1965 [21]. The first commercial product was Shell Chemical s Kraton 101, of styrene polybutadiene-styrene composition. This development led to the carboxy-terminated nitrile (CTBN) rubber modifiers used to flexibilize epoxy and other brittle resin adhesives in the late 1960s. Today, the thermoplastic rubber block copolymer adhesives are used in hot melt-, solvent- and water-based adhesives, and as hot melt- and solvent-based sealants. Major applications are as pressure-sensitive adhesives, construction adhesives and sealants, and general assembly adhesives. 

Thermoplastic rubber is a relatively new class of polymer. It has the solubility and thermoplasticity of polystyrene, while at ambient temperatures it has the toughness and resilience of vulcanized natural rubber or polybutadiene. These rubbers are actually block copolymers. The simplest form consists of a rubbery mid-block with two plastic end blocks (A-B-A), as shown in Figure 5.7. Examples of commercial products are Kraton and Solprene . These materials are often compounded with plasticizers to decrease hardness and modulus, eliminate drawing, enhance pressure-sensitive tack, improve low-temperature flexibility, reduce melt and solution viscosity, decrease cohesive strength or increase plasticity if desired, and substantially lower material costs. Low levels of thermoplastic rubbers are sometimes added to other rubber adhesives. These materials are used as components in the following applications PSAs, hot-melt adhesives, heat-activated-assembly adhesives, contact adhesives, reactive contact adhesives, building construction adhesives, sealants, and binders. Two common varieties of thermoplastic rubber adhesives are styrene-butadiene-styrene (S-B-S) and styrene-isoprene-styrene (S-I-S). ... 

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. 

PP has been recycled from industrial scraps. The melt flow index was about 5.5. Kraton FG 190IX is a triblock copolymer consisting of polystyrene end-blocks and a partly hydrogenated polybutadiene mid-blocks grafted with maleic anhydride, and manufactured by Shell Chemicals. 

A similar block copolymer targeted for the hot melt market has recently been introduced by Firestone. This product, Stereon 840A, is a multiblock styrene-butadiene copolymer. It has a higher styrene content and somewhat lower MW than the Kratons. A typical PSA formulation using Stereon is given in Table 2. 

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