Thermoplastic isoprene rubber

WRDC Wright Research and Development YIR thermoplastic isoprene rubber... 

On the other hand, the mechanical properties of thermoplastic vulcanizates containing ground tire rubber have been investigated with the aim of increasing use of recycled rubber. The compositions tested included passenger car combined with EPDM, SBR rubber, isoprene rubber, and butadiene rubber. It was found that the particle size of the ground tire rubber had small effect on mechanical properties, but that the choice of the sulfur accelerator was significant [26]. 

The most extensively studied block copolymers prepared by anionic polymerization are the styrene-butadiene or styrene-isoprene rubbers. Shell Chemical Company s Kraton thermoplastic elastomers are ABA block copolymers of this type. Their elastomeric properties are excellent, yet they differ from other rubbers in that vulcanization is not required. These elastomers consist of a rubbery polybutadiene matrix with the styrene segments serving as anchors in thermoplastic microdomains. 

Polynorbornene Reclaims and regrinds Reprocessed synthetic Styrene-isoprene rubbers Thermoplastic elastomers Transoctenamer... 

Reinforced reaction injection molding Reinforced thermoplastic Room temperature vulcanization Residual vinyl chloride monomer Chlorinated isoprene rubber (DIN)... 

Block copolymer chemistry and architecture is well described in polymer textbooks and monographs [40]. The block copolymers of PSA interest consist of anionically polymerized styrene-isoprene or styrene-butadiene diblocks usually terminating with a second styrene block to form an SIS or SBS triblock, or terminating at a central nucleus to form a radial or star polymer (SI) . Representative structures are shown in Fig. 5. For most PSA formulations the softer SIS is preferred over SBS. In many respects, SIS may be treated as a thermoplastic, thermoprocessible natural rubber with a somewhat higher modulus due to filler effect of the polystyrene fraction. Two longer reviews [41,42] of styrenic block copolymer PSAs have been published. 

Thermoplastic block copolymers were used for pressure-sensitive and hot-melt rubber adhesives as from the middle sixties. These adhesives found application in packaging, disposable diapers, labels and tapes, among other industrial markets. The formulation of these adhesives generally includes an elastomer (generally containing styrene endblocks and either isoprene, butadiene or ethylene-butylene midblocks) and a tackifier (mainly a rosin derivative or hydrocarbon resin). 

The hydrogenation of the centre block of SBS copolymer produced oxidation stable thermoplastic elastomer. This product was commercialized by the Shell Development Company under the trade name of Kraton G. The field of thermoplastic elastomers based on styrene, 1-3-butadiene or isoprene has expanded so much in the last 10 years that the synthetic rubber chemist produced more of these polymers than the market could handle. However, the anionically prepared thermoplastic system is still the leader in this field, since it produced the best TPR s with the best physical properties. These TPR s can accommodate more filler, which reduces the cost. For example, the SBS Kraton type copolymer varies the monomer of the middle block to produce polyisoprene at various combinations, then, followed... 

Since the review of Voge and Adams [343], not much kinetic research has been carried out on the selective oxidation of olefins with more than four carbon atoms. This is unexpected because isopentenes can be selectively oxidized to isoprene, which is an important material in the production of thermoplastic rubbers. Isopentenes are available from hydrocarbon-conversion operations. 

Natural rubber is a polymer of isoprene- most often cis-l,4-polyiso-prene - with a molecular weight of 100,000 to 1,000,000. Typically, a few percent of other materials, such as proteins, fatty acids, resins and inorganic materials is found in natural rubber. Polyisoprene is also created synthetically, producing what is sometimes referred to as "synthetic natural rubber". Owing to the presence of a double bond in each and every repeat unit, natural rubber is sensitive to ozone cracking. Some natural rubber sources called gutta percha are composed of trans-1,4-poly isoprene, a structural isomer which has similar, but not identical properties. Natural rubber is an elastomer and a thermoplastic. However, it should be noted that as the rubber is vulcanized it will turn into a thermoset. Most rubber in everyday use is vulcanized to a point where it shares properties of both, i.e., if it is heated and cooled, it is degraded but not destroyed. 

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... 

The first commercial thermoplastic elastomers deriving their properties from an ABA block copolymer structure were poly(styrene-isoprene-styrene) and poly (styrene-butadiene-styrene) triblocks introduced in 1965 at an ACS Rubber... 

Rubber has a structure intermediate between thermosets and thermoplastics, with molecular chains linked by sulphur bridges during vulcanization. In pyrolysis, the main material is tyre rubber, a compound of styrene- butadiene- and isoprene-based rubber (SBR), of carbon black, sulphur, vulcanization aids, and zinc oxide. 

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 discovery culminated in the commercial production and the announcement (41) in 1965 of thermoplastic elastomers from block polymers of styrene and butadiene (S-B-S) and of styrene and isoprene (S-I-S). To rubber scientists and technologists the most outstanding property of S-B-S and S-I-S was the unvulcanized tensile strength compared to that of vulcanized NR and vulcanized SBR carbon black stocks. Stress-strain curves, to break, of these latter materials are compared to that of S-B-S in Figure 2. It was pointed out that the high strength of S-B-S must be due to physical crosslinks. 

The ability of living polymers to resume growth with the addition of fresh monomer provides an excellent opportunity for the preparation of block copolymers. For example, if a living polymer with one active end from monomer A can initiate the polymerization of monomer B, then an A-AB-B type copolymer can be obtained (e.g., styrene-isoprene copolymer). If, however, both ends of polymer A are active, a copolymer of the type B-BA-AB-B results. Examples are the thermoplastic rubbers polysty-rene-polyisoprene-polystyrene and poly(ethylene oxide)-polystyrene-poly(ethylene oxide). In principle, for fixed amounts of two monomers that are capable of mutual formation of living polymers, a series of polymers with constant composition and molecular weight but of desired structural pattern can be produced by varying the fraction and order of addition of each monomer. 

Produced by a solution polymerization process, this material exhibited an ordered molecular structure with the styrene monomer located at the ends of the butadiene monomer chain. In addition, other monomers such as isoprene, ethylene, butylene, and others, could be added to the polymer chain, which further modified basic properties. These materials possess a continuous rubber phase for resilience and toughness, and a discontinuous plastic phase for solubility and thermoplasticity. A variety of different grades are also available for this type of SBR, with differences in molecular weight, differences in the types of monomers used, differences in structural configuration, and differences in the ratio of endblock to midblock. Both emulsion and solution polymerized grades of SBR are available as solvent-based and water-based adhesives and sealants. Block copolymers are extensively used for hot melt formulations and both water-based and solvent-based pressure sensitive adhesive applications. Today, SBR elastomers are the most popular elastomers used for the manufacture of adhesives and sealants. 

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. 

During the middle sixties a series of butadiene-styrene and isoprene-styrene block copolymer elastomers were developed. These materials possess typical rubber-like properties at ambient temperatures, but act like thermoplastic resins at elevated temperatures. The copolymers vary from diblock structures of styrene and butadiene ... 

Classification Thermoplastic elastomer Definition Polymer of isoprene major component of natural rubber, also made synthetically avail, in range of std., oil-extended and carbon bik.-filled grades props, vary with catalysts used in mfg. (lithium, titanium)... 

Synonyms SIS Styrene/isoprene/styrene rubber Styrene-isoprene-styrene thermoplastic rubber... 

Styrene/isoprene/styrene rubber Styrene-isoprene-styrene thermoplastic rubber. See Styrene/isoprene/styrene block copolymer Styrene/MA copolymer CAS 9011-13-6... 

Erdogan and co-workers [11] report a MS analysis of the gases evolved during the pyrolysis of NR, butadiene rubber (BR), SBR, styrene-butadiene-styrene (SBS) and styrene-isoprene-styrene thermoplastic elastomers and PS in the low (0-150 amu) mass range, using a quadrupole mass spectrometer. The results are interpreted using the variations in ion ratio as a function of temperature. 

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