Poly isobutylene

Poly(isobutylene) (PIB) is the earliest polyolefin that has been produced on a technical scale. A German patent was filed in 1931 (1), which was eventually published in 1937. Other patents followed (2). In 1938 PIB was marketed as Oppanol B by BASF. Oppau is a district of Ludwigshafen (3). 

However, PIB is mostly manufactured as a block copolymer. Unsaturations in the backbone are common. Thermoplastic elastomers are composed of glassy outer blocks and rubbery inner blocks. Because of the phase separation of the glassy blocks into discrete domains, these materials behave like crosslinked rubbers at low temperatures. However, at elevated temperatures they can be processed in the same way as thermoplastics (4). 

The introduction of halogenated monomers into the backbone results in highly increased vulcanization properties. 

Isobutene Isoprene Divinylbenzene 4-Methylstyrene Basic monomer Comonomer for crosslinking Comonomer for branching and halogenation Comonomer for halogenation 

Using 4-methylstyrene as comonomer results in a saturated backbone that cannot be vulcanized as such. However, the pendant benzene rings can be brominated. Thus pending aromatic bromine moieties can be used as the starting point for vulcanization. 

Monomer Synthesis. Isobutylene is mainly produced from cracked petroleum gases. The cracked gases are passed through sulfuric acid of specific strength so that isobutylene is selectively absorbed and thus separated from butene-1. In this isobutylene synthesis from petroleum, care must be taken to ensure that sulfur compounds are completely removed, since they are poisons toward polymerization catalysts. This danger does not arise when isobutene is obtained by water elimination from isobutanol on passing over AI2O3. 

Polymerization. Isobutylene is polymerized cationically with BF3 with ethylene as solvent at — 80°C. The heat of polymerization is dissipated by the evaporation of the ethylene, which is not polymerized under these conditions (bp — 106°C). By contrast, sulfuric acid, orthophosphoric acid, and, in particular, concentrated hydrochloric and hydrofluoric acids are mainly dimerization reagents. 

The molecular weight is regulated by the addition of n-butene or diisobutene, since these do not polymerize with BF3 alone. Under otherwise identical conditions, the addition of 10% butene to the polymerization mixture reduces the molecular weight from 300,000 to 100,000, while 0.015% diisobutene lowers the molecular weight to about 50,000. 

In industrial polymerizations, isobutylene and diisobutene are liquified separately by cooling with liquid ammonia or ethylene according to the Linde principle and are mixed together in the required quantities, and then this mixture is mixed 1 1 by weight with ethylene, without using pressure, to provide the polymerization mixture. The liquid mixture is passed onto an 18-m-long conveyor belt of stainless steel and mixed with 0.003-1 part of BF3 in liquid ethylene. After 8 s, the mixture on the conveyor belt, which is moving at the rate of 1 m/s, is polymerized, and is removed with a scraper at the other end The nonpolymerized ethylene is removed by evaporation at 50-100°C in a kneader. 

Properties and Applications. Poly(isobutylene) only crystallizes under stress. Because of the low glass-transition temperature (—70°C), its lack of crystallinity, and the somewhat weak intermolecular forces, poly(isobutylene) is an elastomer. The low-molecular-weight material is used as an adhesive 

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Isobutjiene was first polymerized ia 1873. High molecular weight polymer was later synthesized at I. G. Farben by decreasiag the polymerization temperature to —75°, but the saturated, unreactive polymer could not be cross-linked iato a useful synthetic elastomer. It was not until 1937 that poly(isobutylene- (9-isoprene) [9010-85-9] or butyl mbber was iavented at the Standard Oil Development Co. (now Exxon Chemical Co.) laboratories (1). 

Fig. 8. Flow curves of dispersion of 5 % acetylene carbon black (highly active) in poly(isobutylene) for different temperatures (indicated near curves)...

Fig. 9. Concentration dependences of yield stress for low- and high-molecular poly(isobutylene)s filled by highly active carbon black...

Fig. 12. Flow curves of poly(isobutylene), containing different concentrations of active filler (acetylene carbon black). Concentration (in volume percent) is indicated near the curves. A is the region of flow for stresses exceeding the yield stress B is the region directly adjacent to the yield stress...

Fig. 14. Amplitude dependences (y0 is the amplitude of cyclic deformations) of the elastic modulus for frequency a) = 63 s 1 13% dispersion of acetylene carbon black in low- (/) and high-molecular (2) poly(isobutylene)s...

Kennedy, J. P. and Chou,T. Poly (isobutylene-co-fS-Pinene) A New Sulfur Vulcanizable, Ozone Resistant Elastomer by Cationic Isomerization Copolymerization. Vol. 21, pp. 1—39. 

Temp. °C (r-BuX) M xlO3 Poly isobutylene Yield % /-BuCl MeCl MeBr f-BuBr MeCl MeBr f-BuI EtCl Mel... 

Tsou and Measmer examined the dispersion of organosUicates on two different butyl mbbers, namely BIMS and brominated poly(isobutylene-co-isoprene) (BIIR) with the help of small angle X-ray scattering (SAXS), wide angle X-ray scattering (WAXS), atomic force microscopy (AFM), and TEM [91]. There is also a patent on BIMS nanocomposites for low permeability and their uses in tire inner tubes [92]. 

FIGURE 2.11 Plot of oxygen transmission rate versus time for brominated poly(isobutylene-co-isoprene) (BIMS) nanocomposite. 

Song, J., Bodis, J., and Fhiskas, J.E. Direct functionalization of poly isobutylene by living initiation with alpha-methylstyrene epoxide, J. Polym. Set, Polym. Chem., 40, 1005, 2002. 

Brominated poly(isobutylene-co-4-methyl styrene) (BIMS) is often blended with general-purpose mbbers (NR, BR, SBR, etc.) for producing articles such as tire-forming bladders, treads, and side walls. 

FIGURE 11.12 Interaction energy density versus 4-methyl styrene content. (From Raboney, M., Gamer, R.T., Elspass, C.W., and Peiffer, D.G., Phase Behavior of Brominated Poly(Isobutylene-co-4-Methylstyrene)/ General Purpose Rubber Blends. Rubber Division, Proceedings of the American Chemical Society, Nashville, TN, Sept. 29-Oct. 2, 1998, Paper No. 36.)... 

Analogous principles should apply to ionically propagated polymerizations. The terminus of the growing chain, whether cation or anion, can be expected to exhibit preferential addition to one or the other carbon of the vinyl group. Poly isobutylene, normally prepared by cationic polymerization, possesses the head-to-tail structure, as already mentioned. Polystyrenes prepared by cationic or anionic polymerization are not noticeably different from free-radical-poly-merized products of the same molecular weights, which fact indicates a similar chain structure irrespective of the method of synthesis. In the polymerization of 1,3-dienes, however, the structure and arrangement of the units depends markedly on the chain-propagating mechanism (see Sec. 2b). 

Jacob, S, and Kenned /. Synthesis, Characterization and Properties of OCTA-ARM Poly-isobutylene-Based Star Polymers. Vol 146, pp. 1-38. 

Relaxation Poly isobutylene, poly (methyl methacrylate)... 

Brominated diphenyl oxides, 77 461 Brominated epoxies, 70 383 Brominated epoxy ohgomers, 77 470 Brominated epoxy resin, 70 456 Brominated poly(isobutylene-co-p-methylstyrene), 4 438 blends with halobutyl, 4 453 copolymers, 4 446 vulcanization, 4 450 Brominated polystyrene(s), 77 470 474 20 65... 

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