Thermoplastic rubber adhesives

The market is dominated by flexible foam applications (43% in the United States) and rigid and semi-rigid foam (29%). Cast elastomers (4%) and RIM elastomers (3%) have only specialised outlets. The remaining sizeable 21% of the market cover such diverse uses as thermoplastic rubbers, surface coatings, adhesives, sealants and synthetic leathers. 

The applications of rubber as an engineering material almost invariably involve bonding to a rigid substrate or reinforcement. In some instances these bonds need to be established to a fully cured thermoset rubber or a molded thermoplastic rubber, and a wide variety of adhesives suitable for this purpose are available. In... 

Erwins, E.E., St. Clair, D.J., Erickson, J.E. and Korez, W.H., Thermoplastic rubbers ABA block copolymers. In Satas, D. (Ed.), Handbook of Pressure Sensitive Adhesive Technology. Van Nostrand Reinhold, New York, 1989, pp. 317-373. 

Typical formulation of hot-melt rubber adhesive Thermoplastic elastomer 100 phr... 

Isocyanates can be added to solvent-borne CR adhesive solutions as a two-part adhesive system. This two-part adhesive system is less effective with rubber substrates containing high styrene resin and for butadiene-styrene block (thermoplastic rubber) copolymers. To improve the specific adhesion to those materials, addition of a poly-alpha-methylstyrene resin to solvent-borne CR adhesives is quite effective [76]. An alternative technique is to graft a methacrylate monomer into the polychloroprene [2]. 

Shoe adhesives. CR adhesives are used for the permanent attachment of shoe soles. For difficult-to-bond sole materials (plasticized PVC, EVA foaming soles, thermoplastic rubber, SBR) graft polymer solutions of Neoprene AD-G combined with a polyisocyanate provide a good adhesion. Another major area for CR contact adhesives is the manufacture of leather goods, particularly leather shoe sole bonding and belt lamination. 

FIGURE 27.8 T-peel strength values of dichloroisocyanurate (DCI)-treated styrene-butadiene rubber (SBR) (R2 rubber) and thermoplastic rubber (TR)/waterbome polyurethane adhesive/canvas joints. Influence of the dichloroisocyanurate (DCI) concentration. (From Cepeda-Jimenez, C.M., Pastor-Bias, M.M., Martfn-Martfnez, J.M., and GottschaUc, P., J. Adhes. Set Technol., 16, 257, 2002.)... 

Pastor-Bias M.M., Martfn-Martfnez J.M., and Boerio F.J., 2002, Mechanisms of adhesion in surface chlorinated thermoplastic rubber/thermoplastic pol3uirethane adhesive joints. Rubber Chem. Technol., 75(5), 825-837. 

Global consumption of thermoplastic rubbers of all types is estimated at about 600,000 t/yr (51). Of this, 42% was estimated to be consumed in the United States, 39% in Western Europe, and 19% in Japan. At present, the worldwide market is estimated to be divided as follows styrenic block copolymers, 48% hard polymer/elastomer combinations, 26% thermoplastic polyurethanes, 12% thermoplastic polyesters, 4% and others, 9%. The three largest end uses were transportation, 23% footwear, 18% and adhesives, coatings, etc, 16%. The ranges of the hardness values, prices, and specific gravities of commercially available materials are given in Table 4. 

Woo et al. (1994) studied a DGEBA/DDS system with both polysul-fone and CTBN. The thermoplastic/rubber-modified epoxy showed a complex phase-in-phase morphology, with a continuous epoxy phase surrounding a discrete thermoplastic/epoxy phase domain. These discrete domains exhibited a phase-inverted morphology, consisting of a continuous thermoplastic and dispersed epoxy particles. The reactive rubber seemed to enhance the interfacial adhesive bonding between the thermoplastic and thermosetting domains. With 5 phr CTBN in addition to 20 phr polysul-fone, Glc of the ternary system showed a 300% improvement (700 Jm-2 compared with 230 J m 2 for the neat matrix). 

In Japan, pilot plant quantities of rayon and cotton grafted with styrene and other monomers have been prepared and evaluated. Improvements in the flex abrasion resistance and good water repellency were obtained. In addition, thermoplasticity was imparted plus an improved adhesion to rubber. Arthur et al. have also studied this type of grafted cellulose fibers. Again, the work has not led to any large scale developments. Research into grafting to textiles is continuing, but the prospects for any early successful industrialization seem remote. 

Styrene Copolymers. The so-called thermoplastic rubbers based on styrene-butadiene-styrene and styrene-isoprene-styrene block copolymers can be used for hot-melt adhesives, particularly when extended with tackifying resins and oils. They can be made into pressure-sensitive adhesives, as melts with low viscosity—being applied from fine spinnerets which are oscillated to make a... 

Flexibilized epoxy adhesives have moderate strength on flame and corona treated polyolefin substrates. Elevated cure temperature results in better adhesion because of more efficient wetting of the substrate surface. Table 16.13 shows a starting formulation for an epoxy adhesive that develops high peel strength to many difficult-to-bond substrates such as polyethylene, thermoplastic rubber, and polyester film. 

Figure 10. Adhesion and rubber-resin interface in rubber-reinforced thermoplastics...

Styrene/isoprene/styrene (SIS) block copolymer (styrene isoprene ratio of 15/80 to 30/70 by weight) is a thermoplastic rubber. This copolymer can be changed into a good skin adhesive when it is mixed with tackifiers and oils. The advantage of this adhesive is that it can be coated with hot melt coating process... 

This product is an ultraviolet light absorber for use in polystyrene, unsaturated polyesters, coatings, varnishes, lacquers, and coatings based on epoxy or phenolic alkyds. It is also used in pressure sensitive adhesives, polymethylacrylate (fdm or sheeting), thermoplastic rubbers, polyisoprene latex and alcohol based cosmetics. 

Sealz [Uniroyal]. TM for a line of thermoplastic rubber compounds that are used as additives for asphalt and tar products to raise softening point, improve low-temperature flexibility, enhance adhesive quahties, and increase elasticity. 

The Shell Kraton thermoplastic rubbers are based on S-B-S, S-I-S, and S-EB-S. Applications include adhesives, footwear, mechanical goods, and automotive applications. Shell also manufactures S-EP block copolymers under the Shellvis trade name. These are used as viscosity index improvers in lubricating oils. 

Amoco Resin 18. [Amoco] Poly-a-methylstyrene extrusion and mending process aid in ABS, PVC, CPVC, and semirigid vinyl, thermoplastic urethanes, molded rubbers, and thermoplastic elastomers modifier and rein-forcer in adhesives, thermoplastic powd. coatings, hot-mielt coatings. 

Chemlok . [Lrad] Bonding agent, adhesive for rubber, urethanes, polyolefins, thermoplastic elastomers. 

Piccotex . [Hocules] Vinyltoluene/al-pha-methylstyrene copolymer resins thermoplastic used in hot-melts, adhesive systems, rubber compding., specialty paint and lacquer formulations. 

Melt adhesives are based on thermoplastics, but usually contain a number of other components. The most commonly used melt adhesives are based on ethylene-vinyl acetate (EVA) copolymers, but polyethylene, polyesters, polyamides, and thermoplastic rubbers (e.g., styrene-butadiene block copolymers) are also used (see Adhesive Bonding of Plastics in Chapter 2). 

Efforts to bond rubber to metal without the use of metal plating led to what is believed to be the first research efforts in surface preparation prior to adhesive bonding. Strong and durable bonds of rubber to metal were necessary for rubber shock mounts for automobiles in the late 1920s, but they were limited to proprietary formulations used on specific metals. In 1927 solvent-based thermoplastic rubber cements for metal-to-rubber bonding were prepared from rubber cyclized by treatment with sulfuric or other strong acids. With these rubber cements strong bonds could be made to either vulcanized or unvulcanized rubber. 

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. 

The fundamentals of pressure-sensitive hot-melt adhesives are similar to those of solvent-based systems. Most elastomers and tackifiers are suitable, although ethylene-vinyl acetate copolymers are also used and the conventional rubber types are not. Pressure-sensitive hot melts are dominated by thermoplastic rubbers, which are ideal for use in these applications. Their unique properties arise from their essentially two-phase structure, in which thermoplastic regions of styrene end blocks lock the elastomeric midsections of butadiene or isoprene at room temperature but allow the elastomer to move freely at elevated temperatures or in solvent. This gives the polymer properties that are akin to those of vulcanized rubbers at room temperature, while allowinig it to behave as a thermoplastic when heated or dissolved. This structure is illustrated in Fig. 1. 

Chem. Descrip. Wh. mineral oil USP CAS 8042-47-5 EINECS/ELINCS 232-384-2 Uses Base in laxatives, cosmetic aeams, btions, sunscreens, foods (bakery pan oils, lubes/greases, food pkg.) plasticizer, lubricant for PS, ethylcellulose, PVC, annealing, catalyst carriers, thermoplastic rubber, adhesives, household cleaners and polishes water repellent for paper protective coating on foods... 

Chem. Desaip. Carbon black CAS 1333-86-4 EINECS/ELINCS 215-609-9 Uses Conductive filler for elec, conductive and antistatic compds., incl. thermoplastics, rubber, adhesives, sealants, inks, coatings, putties, floor pavements, concrete, mortar, paper for conductor insulation Features Porous results in lower compding. vise., easier processing, lower moisture pickup during compding., storage, and transportation, improved physical props. 

Uses Antioxidant for rubber goods esp. latex applies., polyamides, polyesters, POM, PVC, PS, EVA hot melts, thermoplastic rubber, styrenics, cellulosics in food-pkg. adhesives antioxidant in food-contact rubber articles for repeated use antioxidant/stabilizer for food-grade polymers Regulatory FDA21CFR 175.105,177,2600,178,2010 Manuf/Distrib. Goodyear R.T. Vanderbilt Trade Names Ralox LC... 

Zinc 0,0-dihexyl dithiophosphate. See Zinc dihexyl dithiophosphate Zinc diisobutyidithiocarbamate CAS 36190-62-2 Synonyms Zinc, bis(bis(2-methylpropyl)carbamodithioato-S,S> Properties M.w. 474.13 Uses Accelerator for rubber antioxidant in thermoplastic rubber, NR, SR, MR, adhesives, cements, hot melts, and latex Trade Name Synonyms Isobutyl Zimate [R.T. Vanderbi It http //www.rtvanderbilt.com]... 

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