Polypropylene and Polyisobutylene

Since on the PP macrochain every second carbon atom is tertiary and in polyisobutylene (PIB) it is quaternary, then the strength of the carbon-carbon bonds falls going from PE, throngh PP to PIB. 

This is clearly confirmed by the data on the thermal degradation of propylene and PIB under vacnnm (Table 1.3). Comparison of the number of volatile products released at corresponding temperatures has shown that PIB is less thermally stable than PP thus the PP half-life temperature is 387 °C, while that of PIB is 344 C. 

Decomposition temperature (°C) Quantity of volatiles (%) Decomposition temperature (°C) Quantity of volatiles (%) 

Mass spectroscopic analysis of the volatile fractions released by PP during its half-life at 380-410 °C has shown that butane, butane, hexane, hexene, pentane, pentene and propylene are the main products of decomposition. 

the tertiary hydrogen atom is more reactive, undergoing scission more readily than the secondary hydrogen atom. Accordingly, bond cleavage in the polymer chain occurs mainly with the transfer of an hydrogen atom  

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Enhanced radiation cross-linking in polyethylene, polypropylene and polyisobutylene,43 and in copolymers of ethylene and propylene,44 was found when nitrous oxide was incorporated into the polymer matrix. Mechanisms of this process have been proposed by several researchers.45 17... 

Several graft copolymerizations were described by Ballantine (17, 64), Henglein (104, 105) and coworkers. Different monomer-polymer systems were examined styrene on polymethyl methacrylate, poly-2, 5-dichlorostyrene, polytetrafluoroethylene, polyethylene, polypropylene and polyisobutylene, acrylonitrile on polyethylene, rubber, polymethyl methacrylate and dimethyl polysiloxane, vinylpyrrolidone and acroleine on polymethyl methacrylate. The results agree with the preceding ones moreover they show the influence of the swelling and diffusion of the monomer into the polymer. 

Hexahydropyrene sensitized chain scission of polypropylene and polyisobutylene during light irradiation Q20).Polycyclio hydrocarbons have a important role in sensitized photooxidation of polyisoprene (122).polys tyrene (123) poly(methyl methacrylate) (123-126). It is quite probable that these reactions can also occur with participation of singlet oxygen. 

Photolysis of polypropylene and polyisobutylene containing aromatic impurities/ Polycrystalline EPR/ 77 3H 2.3 71Bail/ 69Mall... 

POLYALKENE AND DIENE POLYMERS 15.5.1 Polyethylene, Polypropylene and Polyisobutylene... 

Other Uses. Large quantities of hydrocarbon resins are used in mastics, caulks, and sealants (qv). Polymers for these adhesive products include neoprene, butyl mbber, polyisoprene, NR, SBR, polyisobutylene, acryHcs, polyesters, polyamides, amorphous polypropylene, and block copolymers. These adhesives may be solvent or water-borne and usually contain inorganic fillers. 

Barrier Properties. VinyUdene chloride polymers are more impermeable to a wider variety of gases and Hquids than other polymers. This is a consequence of the combination of high density and high crystallinity in the polymer. An increase in either tends to reduce permeabiUty. A more subtle factor may be the symmetry of the polymer stmcture. It has been shown that both polyisobutylene and PVDC have unusually low permeabiUties to water compared to their monosubstituted counterparts, polypropylene and PVC (88). The values Hsted in Table 8 include estimates for the completely amorphous polymers. The estimated value for highly crystalline PVDC was obtained by extrapolating data for copolymers. 

In principle, A can be any polymer normally regarded as a hard thermoplastic, eg, polystyrene, poly(methyl methacrylate), or polypropylene, and B can be any polymer normally regarded as elastomeric, eg, polyisoprene, polybutadiene, polyisobutylene, or polydimethylsiloxane (Table 2). 

A third factor influencing the value of Tg is backbone symmetry, which affects the shape of the potential wells for bond rotations. This effect is illustrated by the pairs of polymers polypropylene (Tg=10 C) and polyisobutylene (Tg = -70 C), and poly(vinyi chloride) (Tg=87 C) and poly(vinylidene chloride) (Tg =- 19°C). The symmetrical polymers have lower glass transition temperatures than the unsymmetrical polymers despite the extra side group, although polystyrene (100 C) and poly(a-meth-ylstyrene) are illustrative exceptions. However, tacticity plays a very important role (54) in unsymmetrical polymers. Thus syndiotactic and isoitactic poly( methyl methacrylate) have Tg values of 115 and 45 C respectively. 

The principal polyolefins are low-density polyethylene (ldpe), high-density polyethylene (hope), linear low-density polyethylene (lldpe), polypropylene (PP), polyisobutylene (PIB), poly-1-butene (PB), copolymers of ethylene and propylene (EP), and proprietary copolymers of ethylene and alpha olefins. Since all these polymers are aliphatic hydrocarbons, the amorphous polymers are soluble in aliphatic hydrocarbon solvents with similar solubility parameters. Like other alkanes, they are resistant to attack by most ionic and most polar chemicals their usual reactions are limited to combustion, chemical oxidation, chlorination, nitration, and free-radical reactions. 

Polypropylene. A similar study on polypropylene is interesting because polypropylene has a molecular structure intermediate between polyethylene and polyisobutylene. An atactic polypropylene specimen was prepared by ether extraction and irradiated in a nitrous oxide atmosphere. The changes in gel fraction (insoluble in hot xylene) as a function of N-jO pressure are shown in Figure 6. Gel formation (cross-linking) of polypropylene is also promoted in the presence of nitrous oxide. 

From industry s viewpoint, the action of nitrous oxide should be useful to cut down the dose required for the crosslinking of polyethylene or polypropylene and to keep polyisobutylene from degradation. However, it is a question whether the complexity of processing caused by using nitrous oxide would pay economically. 

Polyethylene and polyisobutylene Polyethylene and polypropylene (5% PE in PP) Polycarbonate and polyethylene teraphthalate... 

End-functionalized polyethylene (PE) [8, 9], polypropylene (PP) [10], and polyisobutylene (PIB) [11] have been transformed to their corresponding macromonomers carrying (meth)acrylate, oxazoline, and methacrylate end groups, 1, 2, and 3, respectively. Polybutadienyl lithium was terminated with chlo-rodimethylsilane, followed by hydrogenation to saturated polyolefin (PHBd) [12]. Hydrosilylation of the end silane with allyl glycidyl ether afforded an epox-... 

Within the family of polyolefins there are many individual families that include low density polyethylenes, linear low density polyethylenes, very low polyethylenes, ultra low polyethylenes, high molecular weight polyethylenes, ultra high molecular weight polyethylenes, polyethylene terephthalates, ethylene-vinyl acetate polyethylenes, chlorinated polyethylenes, crosslinked polyethylenes, polypropylenes, polybutylenes, polyisobutylene, ionomers, polymethylpentene, thermoplastic polyolefin elastomers (polyolefin elastomers, TP), and many others. 

Polyvinyl chloride, rigid/plasticized laminate (top temperature 140°F) Polypropylene (and system to bond it without laminate backing) Polyisobutylene rubber (top temperature 180°F),and probably others... 

Temperature dependence of x for mixtures of polyisobutylene and deuterated head-to-head polypropylene and the calculated phase diagram from Flory-Huggins theory with... 

Geometric factors, such as the symmetry of the backbone and the presence of double bonds on the main chain, affect Tg. Polymers that have symmetrical structure have lower Tg than those with asymmetric structures. This is illustrated by two pairs of polymers polypropylene vs. polyisobutylene and poly(vinyl chloride) vs. poly(vinylidene chloride) in Table 4.4. Given our discussion above on chain stiffness, one would have expected that additional groups near the backbone for the symmetrical polymer would enhance steric hindrance and consequently raise Tg. This, however, is not the case. This discrepancy is due to conformational requirements. The additional groups can only be accommodated in a conformation with a loose structure. The increased free volume results in a lower Tg. 

CD can react with the linear polymers including some hydrophilic chemicals, for instance, polyethylene glycol (PEG), polypropylene glycol (PPG), and perfluoromethyl vinyl ether (PMVE), or some lipophilic chemicals, for example, low-density polyethylene (LDPE), polypropylene (PP), polyisobutylene imide (PIBI), polyester for the production of rotaxane and n-rotaxane. PEG is mixed with CD to achieve the precipitation. The yield increases with the increase in... 

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