Polyisobutene

In this polymer, every alternate carbon of the chain is quaternary and no reactive hydrogen atoms are present. Formation of radicals by scission of the main chain results in monomer formation by a chain depolymerization [51, 52, 54, 55], but the polymer is not quantitatively converted into monomer as happens with polymethylmethacrylate. A range of products from C4 to C2 0 is also evolved [52, 53]. 

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Pathmamanoharan C and Philipse A P 1998 Preparation and properties of monodisperse magnetic cobalt colloids grafted with polyisobutene J. Colloid Interface Sol. 205 304-53... 

Methylpropene H2C = C(CH3)2 CH3 Polyisobutene is component of butyl rubber one of earliest syn thetic rubber substitutes... 

Mascaramatic mascaras have the largest share of the market. Emulsion mascaramatics are cream-type mascaras dispensed from containers that include a closure provided with a wand ending in a small bmsh. In solvent mascaramatics, mascara masses are pigment suspensions in thickened hydrocarbon solvents such as isoparaffins and petroleum distillates. The thickeners include waxes (microcrystalline [63231 -60-7] camauba [8015-86-9] or ouricury [68917-70-4], polymers (hydrogenated polyisobutene [61693-08-1]), and esters (propylene glycol distearate [6182-11-2] or trilaurin [538-24-9]). 

Whilst polyisobutene is a non-rubbery polymer exhibiting high cold flow (see Section 11.3), the copolymer containing about 2% isoprene can be vulcanised with a powerful accelerated sulphur system to give moderately rubbery polymers. The copolymers were first developed in 1940 by Esso and are known as butyl rubbers and designated as HR. As they are almost saturated they have many properties broadly similar to the EPDM terpolymers. They do, however, have two properties that should be particularly noted ... 

Standard-grade PSAs are usually made from styrene-butadiene rubber (SBR), natural rubber, or blends thereof in solution. In addition to rubbers, polyacrylates, polymethylacrylates, polyfvinyl ethers), polychloroprene, and polyisobutenes are often components of the system ([198], pp. 25-39). These are often modified with phenolic resins, or resins based on rosin esters, coumarones, or hydrocarbons. Phenolic resins improve temperature resistance, solvent resistance, and cohesive strength of PSA ([196], pp. 276-278). Antioxidants and tackifiers are also essential components. Sometimes the tackifier will be a lower molecular weight component of the high polymer system. The phenolic resins may be standard resoles, alkyl phenolics, or terpene-phenolic systems ([198], pp. 25-39 and 80-81). Pressure-sensitive dispersions are normally comprised of special acrylic ester copolymers with resin modifiers. The high polymer base used determines adhesive and cohesive properties of the PSA. 

Plastic Propellant The Tensile Properties of the Polyisobutene Binder , ERDE Tech Memo No 15/M/64, Waltham Abbey (Engl) (1964)... 

Chlorine caused a significant temperature rise when it came into contact with polyisobutene. 

Polymers which give mouldable propellants are mixed with the oxidiser in a similar manner, but the product is usually worked mechanically between rolls and evacuated to remove air bubbles. The powder is then moulded by pressure into the metal casing. Alternatively, such plastics can give a propellant which can be extruded into charges which are afterwards cut and machined to suitable shape. The Rocket Propulsion Establishment at Westcott has used ammonium perchlorate and polyisobutene to produce a propellant of putty-like consistency. 

Mixtures of silver peroxide with 1% of polyisobutene exploded on 3 separate occasions. Use of a halogenated polymer was safe. 

Cosmetic Compositions including Polyisobutene. U.S. Patent 5695772, December 9, 1997. 

Cosden A process for polymerizing isobutene to a polyisobutene having a molecular weight between 300 and 2,700. 

Hydrogenated MDI (HMDI), 25 463 Hydrogenated palm kernel glycerides, cosmetically useful lipid, 7 833t Hydrogenated polyisobutene, in mascara, 7 862... 

The most important limitation of polyisobutene is its tendency to cold flow because of which it cannot be used in self-supporting forms. This defect can be overcome by copolymerisation with isoprene and vulcanisation of product with sulphur. The product is called butyl rubber. This product was first marketed in 1943 in USA. 

Polyisobutene has a regular head-to-tail structure, and the crowding of the methyl groups is so great that the molecule can only be built from conventional atomic models with great... 

The nature and proportions of different kinds of end-groups in polyisobutenes depend upon the catalytic system and the solvent used in their preparation. 

With co-catalysts other than water, a part of the co-catalyst may also form an end-group by a termination reaction. When trichloroacetic acid was used as co-catalyst with titanium tetrachloride, trichloroacetate end-groups were found on the polyisobutenes [9, 10]. 

The proportions of the different kinds of initial groups depend on the nature and rate of the different transfer reactions by which they are formed and the proportion of initial groups derived from the catalyst will depend on the ratio of the rate of initiation to the sum of the rates of the transfer reactions. Finally, although the main chain of the polyisobutene molecule is very resistant to chemical attack [14], by virtue of its chemical structure and configuration, the end-groups are readily attacked by atmospheric oxidation. 

This is obvious from the prominent carbonyl bands in the IR spectra of polyisobutenes which have been heated in air [15]. This indicates how important it is to handle carefully polymers which are to be used for end-group studies. 

In many places in the text of Ref. [53] and in the caption to Table II, isobutene is used erroneously in place of polyisobutene . On p. 487 the DP of styrene should be the DP of polystyrene . - The following corrections should also be noted ... 

Footnote In the captions to all the figures in this paper DP of isobutene should read DP of polyisobutene . Note also the following corrections ... 

Methyl chloride labelled with 14C was used both as vehicle for the catalyst and as solvent for the isobutene in reactions carried out at -78°. Polyisobutene equivalent to 82.2 per... 

Figure 6 The effect of n-butyraldehyde on the specific conductivity of 8.1 x 10"3 mole/1. A1C13 in C2H5C1 at -80° and on the DP of polyisobutenes formed in these solutions [66]...

The effects of the non-polar additives benzene and cyclohexane were compared [69] by studying the effect (at -78.5°) of increasing concentrations of these compounds on the conductivity of solutions of A1C13 and of EtOHAlCl3 in ethyl chloride, and on the DP of the polyisobutenes formed in these solutions. 

Since there is a close correlation between the specific conductivity of the catalytic solutions and the DP of the polymers formed in them, it follows that the electrochemical nature of the solutions must be largely unaffected by the polymerisation. Therefore at most a small fraction of the solute can be involved with the growing chain, and the remainder must be unaffected by the initiation of the polymerisation. This conclusion is strongly supported by the fact that in typical experiments the number of moles of polyisobutene formed was several powers of ten smaller than the number of moles of catalytic complex. 

In the range of concentrations where the inverse correlation between specific conductivity of the catalytic solution and the DP of the polyisobutene formed in it prevails, the principal chain breaking agents must be free ions, the nature and concentration of which are probably very similar to those prevailing before the addition of the monomer. 

Kinetic studies on the polymerisation of isobutene at low temperatures by titanium tetrachloride in various solvents form the subject of a series of papers by Plesch and his co-workers [9, 10, 13, 28, 32, 33, 71, 77, 80, 81]. The reactions were followed in an apparatus approximating to an adiabatic calorimeter by means of the temperature rise accompanying the polymerisation. In the early studies moisture was not rigorously excluded from the systems, but later [81] an elaborate vacuum technique was evolved and all reagents were carefully purified and dried. Titanium tetrachloride was also used as catalyst by Okamura and his collaborators [79] in a series of studies concerning the effects of solvent, catalyst, and co-catalyst on the DP of polyisobutene. 

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