Polyisoprene polybutadiene

The economic importance of copolymers can be cleady illustrated by a comparison of U.S. production of various homopolymer and copolymer elastomers and resins (102). Figure 5 shows the relative contribution of elastomeric copolymers (SBR, ethylene—propylene, nitrile mbber) and elastomeric homopolymers (polybutadiene, polyisoprene) to the total production of synthetic elastomers. Clearly, SBR, a random copolymer, constitutes the bulk of the entire U.S. production. Copolymers of ethylene and propylene, and nitrile mbber (a random copolymer of butadiene and acrylonitrile) are manufactured in smaller quantities. Nevertheless, the latter copolymers approach the volume of elastomeric butadiene homopolymers. 

AA Natural rubber, styrene butadiene, butyl, ethylene propylene, polybutadiene, Polyisoprene... 

Natural rubber Styrene-butadiene rubber Polybutadiene Polyisoprene Nitrile rubber Halogenated nitrile rubber Ethylene-propylene rubber EPDM... 

Unlike polybutadiene, polyisoprene prepared at low temperatures shows little or no inclination to crystallize either on stretching or cooling. This may seem surprising in view of the even greater preponderance of trans-1 4 units in polyisoprene than in poly butadiene. The explanation for the contrasting behavior in this respect between low temperature synthetic polyisoprene, on the one hand, and guttapercha and low temperature polybutadiene, on the other, probably is to be found in the appreciable occurrence of head-to-head and tail-to-tail sequences of 1,4 units of the former. 

The method is based on the fact that the rate of conformational change required for excimer formation depends on the free volume induced by the segmental motions of the polymer occurring above the glass transition. DIPHANT (compound 3 in Figure 8.3) was used as an excimer-forming probe of three polymer samples consisting of polybutadiene, polyisoprene and poly(dimethylsiloxane).a)... 

Many of the synthetic elastomers now made are still polymerized by a free radical mechanism. Polychloroprene, polybutadiene, polyisoprene, and styrene-butadiene copolymer are made this way. Initiation by peroxides is common. Many propagation steps create high molecular weight products. Review the mechanism of free radical polymerization of dienes given in Chapter 14, Section 2.2. 

Polyesters, polyurethanes Polyesters, nylons, polyurethanes Polypropylene, LDPE, PMMA, poly(alpha-methylstyrene) Polybutadienes, polyisoprene... 

Over 5.5 billion pounds of synthetic rubber is produced annually in the United States. The principle elastomer is the copolymer of butadiene (75%) and styrene (25) (SBR) produced at an annual rate of over 1 million tons by the emulsion polymerization of butadiene and styrene. The copolymer of butadiene and acrylonitrile (Buna-H, NBR) is also produced by the emulsion process at an annual rate of about 200 million pounds. Likewise, neoprene is produced by the emulsion polymerization of chloroprene at an annual rate of over 125,000 t. Butyl rubber is produced by the low-temperature cationic copolymerization of isobutylene (90%) and isoprene (10%) at an annual rate of about 150,000 t. Polybutadiene, polyisoprene, and EPDM are produced by the anionic polymerization of about 600,000, 100,000, and 350,000 t, respectively. Many other elastomers are also produced. 

Static H 2D NOE spectroscopy was applied in a first experiment showing that the technique can be used to measure inter-chain interactions [44], This work was then continued by applying the technique under MAS to investigate the inter-molecular interactions responsible for the miscibility in polybutadiene/polyisoprene blends above the Tg [45]. It was shown that intermolecular association can be probed by this technique and the results reveal the existence of weak intermolecular interactions between the polyisoprene methyl group and the vinyl side chain of the polybutadiene. 

Poly(methyl acrylate) Poly(methyl methacrylate) Polyacrylonitrile Polymethacrylonitrile Polybutadiene Polyisoprene Polychloroprene Poly(methylene oxide) Poly(ethylene oxide) Poly(tetramethylene oxide) Poly(propylene oxide) Poly(hexamethylene succinate) Poly(hexamethylene sebacate) Poly(ethylene terephthalate) Nylon 6 Polycarbonate... 

Block copolymers themselves are also finding rapidly expanding applications on an industrial scale. A sandwich copolymer (triblock) with an elastomeric core (polybutadiene, polyisoprene, etc.) and plastomeric ends (polystyrene, etc.) represents a physically vulcanizing rubber (plastomeric elastomer). It can be processed above the glass transition temperature of the plastomeric blocks by work-efficient technologies (injection molding, extrusion, etc.). At temperatures below the Tg of the plastic blocks, the copolymer behaves as vulcanized rubber. 

Polybutadiene, polyisoprene Polyesters, polyurethanes, polyamides (nylons) Polyacetals, polycarbonates Polytirethanes, polyesters, nylons Polyether-polyurethane... 

Fig. 9. A comparison of the late stage scaling function of near critical polybutadiene/polyisoprene (PB/PI) mixtures at T = 55 °C with that of deuterated poly-butadiene/polybutadiene mixture [36], DPB/PB and of an iso-butyric acid/water mixture [181] I/W. Note the asymptotic exponents F(x < 1) ocx and F(x > 1) ocx-4. From Takenaka and Hash-imoto [180]...

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