ISOPRENE COPOLYMER

G-5—G-9 Aromatic Modified Aliphatic Petroleum Resins. Compatibihty with base polymers is an essential aspect of hydrocarbon resins in whatever appHcation they are used. As an example, piperylene—2-methyl-2-butene based resins are substantially inadequate in enhancing the tack of 1,3-butadiene—styrene based random and block copolymers in pressure sensitive adhesive appHcations. The copolymerization of a-methylstyrene with piperylenes effectively enhances the tack properties of styrene—butadiene copolymers and styrene—isoprene copolymers in adhesive appHcations (40,41). Introduction of aromaticity into hydrocarbon resins serves to increase the solubiHty parameter of resins, resulting in improved compatibiHty with base polymers. However, the nature of the aromatic monomer also serves as a handle for molecular weight and softening point control. 

A living cationic polymeriza tion of isobutylene and copolymeriza tion of isobutylene and isoprene has been demonstrated (22,23). Living copolymerizations, which proceed in the absence of chain transfer and termination reactions, yield the random copolymer with narrow mol wt distribution and well-defined stmcture, and possibly at a higher polymerization temperature than the current commercial process. The isobutylene—isoprene copolymers are prepared by using cumyl acetate BCl complex in CH Cl or CH2CI2 at —30 C. The copolymer contains 1 8 mol % trans 1,4-isoprene... 

Polyisobutylene and isobutylene—isoprene copolymers are considered to have no chronic hazard associated with exposure under normal industrial use. Some grades can be used in chewing-gum base, and are regulated by the PDA in 21 CPR 172.615. Vulcanized products prepared from butyl mbber or halogenated butyl mbber contain small amounts of toxic materials as a result of the particular vulcanization chemistry. Although many vulcanizates are inert, eg, zinc oxide cured chlorobutyl is used extensively in pharmaceutical stoppers, specific recommendations should be sought from suppHers. 

Until the mid-1950s the only polyolefins (polyalkenes) of commercial importance were polyethylene, polyisobutylene and isobutylene-isoprene copolymers (butyl rubber). Attempts to produce polymers from other olefins had, at best, resulted only in the preparation of low molecular weight material of no apparent commercial value. 

Compound A—A blend of cured and uncured isobutylene-isoprene copolymer... 

Compound A was affected most by the irradiation, Compound B least, and Compound C intermediate. The effect of the irradiation on cohesion increased with increasing irradiation dose and temperature. The iso-butylene-isoprene copolymer in Compound A and Compound C degrades during irradiation (9), becoming softer after irradiation. Since the seam of a can is formed before irradiation, some softening of the compound in the seam is not detrimental to the integrity of the seam. 

Table IV shows the data on rigidity changes of the end-sealing compounds at two dose levels. Rigidity was determined by torsional braid analysis (5). These data indicate that the blend of cured and uncured isobutylene-isoprene copolymer was softened most by the irradiation treatment, the blend of polychloroprene and butadiene-styrene copolymer softened the least, and the blend of polychloroprene and the uncured isobutylene-isoprene copolymer was intermediate. Increasing the irradiation dose from 3-4 Mrad to 6-7.5 Mrad decreased the rigidity of the three end-sealing compounds. The irradiation temperature did not significantly influence rigidity.

The production test showed that the epoxy phenolic enamel was the preferred enamel for coating tinplate containers used in packaging irradiation-sterilized ham and beef. The preferred end-sealing compound for the same application was the blend of cured and uncured isobutylene-isoprene copolymer. 

The evaluation of the components of the tinplate container showed that the preferred enamel for irradiation processing was the epoxy phenolic the preferred end-sealing compound was the blend of cured and uncured isobutylene—isoprene copolymer. Component testing of tinplate and solder for possible changes in mechanical properties, microstructure, and corrosion resistance indicated that the radiation caused... 

Figure 3. Melting points of butadiene-isoprene copolymers. DSC at 20°C/min...

Figure 4. BR + IR is a 50/50 (wt) blend of synthetic cis-1,4-polyisoprene and cis-1,4-polybutadiene. Bl copolymers are random cis-1,4-butadiene-isoprene copolymers with the same composition. Results obtained with Rheovibron on gum vulcanizates at 110 Hz frequency.

Titanocene (Cp2TiR2) /alkyllithium (LiR) Styrene, butadiene or isoprene copolymers PB in cyclohexane and toluene (5 wt.%) Catalyst (bis(cyclopentadienyl) titanium dichloride) 0.4 mmol per 100 g PB PH2 0.49 MPa T 40 °C t 2 h Conversion 97% Asahi Kasei Kogyo Kabushiki Kaisha (Osaka, Japan) 62 (1985)... 

Now again, a state of inhomogeneity in polymers, so especially interesting in films and interfaces, occur when discontinuities are built into the main valence chains and networks. Block polymers are the classic embodiments of this. Many periodic distances separating domains in such alternating or rhymthic copolymers have been reported. These indicate existence of phases in laminar domains and, in other cases, of spherical domains.(51) Cases are shown experimentally for styrene/isoprene copolymers and also for styrene/butadiene.(52,53,54)... 

DENDRIGRAFT (ARBORESCENT)-POLY(STYRENE)-GRAFT-POLY(ISOPRENE) COPOLYMERS... 

Akbulut and Toppare also found very similiar effects upon copolymer composition, total conversion and R.M.M. control in the styrene-isoprene copolymer system [83] with the analogous traces to Figs. 6.19 and 6.20 shifted to slightly more anodic values and with a better total conversion at high potential in the presence of 25 kHz ultrasound. 

Hydroxpropyl Cellulose Hydroxypropyl Methylcellulose Isobutylene-Isoprene Copolymer Locust Bean Gum... 

A rather unusual Fe(III) species for catalysis is [Cp2Fe]+, ferrocenium. A polymer-bound ferrocenium catalyst was obtained by oxidizing a poly(vinylferrocene-folock-isoprene)copolymer with AgOTf. The activity of this catalyst was tested with the reaction of P-oxo ester 24a and MVK (41a) (cf. Scheme 8.27) [93]. 

In the copolymerisation of butadiene and isoprene with Ti-based catalysts, both monomeric units of the copolymers obtained are essentially of a ciy-1,4 structure the microstructure of monomeric units in the copolymers does not differ substantially from that in the homopolymers [196-198], Nd-based catalysts provide butadiene/isoprene copolymers with more than 95% cis-1,4 monomeric units [89,199,200], On the other hand, Co-based catalysts give copolymers in which the structure of the monomeric units depends markedly on copolymer composition [19,201,202], Similarly, the structure of the monomeric units depends on copolymer composition in copolymers of butadiene and 2,3-dimethylbutadiene obtained by copolymerisation with Co-based catalysts [201,203],... 

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