Thermoplastic rubbers, performance

Increased use of thermoplastic rubbers and high-performance rubbers... 

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 vulcanizates (TPVs) are composed of a vulcanized rabber component, such as EPDM, nitrile rubber, and butyl rubber in a thermoplastic olelinic matrix. TPVs have a continuous thermoplastic phase and a discontinuous vulcanized rubber phase. The most common TPV polymer systan is PP/EPDM rubber however, a number of other polymer systems have been commercially developed. These include PP/NBR, PP/butyl and PP/halobutyl, PP/NR, and PP/EVA/EPDM. Producers include Advanced Elastomers Systems (Santoprene, Geolast, and Trefsin). The highly rubberlike properties of TPV have enabled than to perform as engineered thermoplastic rubbers. In numerous application areas they have directly replaced premium-performance thermoset rubber compounds. Prominent among these are dananding automotive applications, electrical insulation and connectors, compression seals, appliance parts, medical devices, and food and beverage contact applications. 

Elastomer that processes as thermoplastic or thermoplastic that performs as thermoset rubber. 

Elastic Attachment Adhesives. These thermoplastic rubber-based adhesives are usually applied by spraying at 140-165 °C. As difierent elastic materials are used, different adhesives need to be formulated to ve the right adhesion performance for each substrate. 

Resins for use with thermoplastic rubbers are selected to perform one or more functions. To aid in the selection process, resins can be grouped first according to their tendency to associate with one phase or the other in thermoplastic rubber. Within these groups, other subdivisions can be made depending on the effect on adhesive properties. 

Plasticizers may perform the following useful functions in adhesives based on thermoplastic rubbers 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 raw material costs. The... 

Selecting a Plasticizer for High Performance Adhesives. The ideal plasticizer for use with thermoplastic rubbers in high performance adhesives is one which is completely insoluble in the endblock phase, completely miscible with the midblock phase, and low in cost. Low volatility, low viscosity, low density, and resistance to degradation are also desirable characteristics. Various hydrocarbon oils whose average solubility parameters are below those of the midblocks, but not too far below, satisfy these requirements reasonably well. 

Oxygen bomb testing (exposure to pure oxygen at 300 psig and I58°F) is often used in the evaluation of construction and other types of adhesives required to perform for periods of many years. Formulated S-B-S thermoplastic rubber films stabilized with 2 to 5 phr of antioxidants selected from Table 6 have retained flexibility for more than 1, (XK) hr in the oxygen bomb. 

In general, each new adhesive product must meet a definite set of performance specifications and must fall within certain manufacturing cost limitations. How is a thermoplastic rubber formulation developed to match such requirements One effective approach is outlined below ... 

Report 86 High Performance Engineering Plastics, D.J. Kemmish, Victrex Ltd. Report 113 Rubber-Modified Thermoplastics, H. Keskkula, University of Texas at Austin. 

Jha A., Dutta B., and Bhowmick A.K., Effect of fillers and plasticizers on the performance of novel heat and oil-resistant thermoplastic elastomers from nylon-6 and acrylate rubber blends, J. Appl. Polym. Sci., 74, 1490, 1999. 

Another example where antioxidant performance can be improved dramatically lies in the mechanochemlcally initiated addition of reactive antioxidants on rubbers (5.10) or unsaturated thermoplastics such as ABS (12). For example, using thiol antioxidants 2 and 3 as the reactive antioxidants, Kharasch-type addition of the thiol function to the polymer double bond takes place during melt processing to give bound antioxidant adduct (see Equation 1) the polymer becomes much more substantive under aggressive environments. 

On the other hand, silicones are used in organic composites. The application of alloys composed of the fully cured silicone rubber particles in a continuous thermoplastic phase, called thermoplastic silicone vulcanizate, which offers high-performance materials, has been reported.506,507 Functionalized POSS was not only co-polymerized, but also blended with poly(methylmethacrylate) to study the effect of silsesquioxanes on the thermal stability of thermoplastics.508... 

Novel styrenic-based TPEs based on blends of a thermoplastic (polystyrene or styrene acrylonitrile) with a rubber (styrene butadiene or ethylene vinylacetate), with special reference to compatibilization and dynamic vulcanization, were reported by Patel et al. The performance properties were correlated with the interaction parameter and the phase morphology of the blend components [62]. 

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