Thermal decomposition products of polyisobutylene

Tsuchiya, Yoshio; Sumi, Kikuo

doi:10.1002/pol.1969.150070302

Cited by 47 publications

(27 citation statements)

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“…works on polyethylene [1][2][3], polypropylene [4][5][6], polystyrene [7][8][9] and polyisobutylene [10][11][12]. But none of them have taken notice of an effect of pressure on thermal degradation of polymers.…”

Section: Introductionmentioning

confidence: 99%

Effect of pressure on thermal degradation of polyethylene

Murata

Sakai

Sakata

2004

Journal of Analytical and Applied Pyrolysis

142

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Section: Introductionmentioning

confidence: 99%

Effect of pressure on thermal degradation of polyethylene

Murata

Sakai

Sakata

2004

Journal of Analytical and Applied Pyrolysis

142

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“…The yield of monomer increases [8] in the range 300 to 400 ~ as the temperature increases. With the exception of the activation energy cited in reference [4], the activation energy appears to be ~ 49 kcal/mole (200 k J/mole) over a wide range of temperature (250" in reference [10], 306 to 326 ~ in reference [13} and 365 to 405 ~ here).…”

Section: Resultsmentioning

confidence: 95%

“…Tsuchiya and Sumi [8] analyzed the products of thermal degradation using gas and liquid phase chromatography. Conditions were similar to those of Madorsky and Straus [3].…”

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confidence: 99%

Thermal degradation of polyisobutylene studied using factor-jump thermogravimetry

Dickens

1983

Journal of Thermal Analysis

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The overall activation energy of the thermal degradation of polyisobutylene has been measured using factor-jump thermogravimetry to be 206 + 1 k J/mole over the range 365 to 405 ~ in N 2 at 800 mm Hg pressure and flowing at 4 mm/s over the sample. This is consistent with some values reported for thermal degradation in vacuum and in solution. In 5 mm Hg of N2, an apparent activation energy of 218 • 2 k J/mole was found, nnd in vacuum the apparent activation energy is 238 • 13 k J/mole. Troublesome bubbling made the vacuum values difficult to measure. Substitution of reasonable values for the activation energies of initiation, E i, termination, Et, and the activation energy, E a, for vacuum degradation in the equation Polyisobutylene (PIBu) has the formula -[C(CH3)2-CH2] n-and hence ideally contains no tertiary carbon atoms. Its thermal degradation in vacuum was studied by Madorsky and coworkers [1], who heated samples of PIBu to temperatures between 313 and 460 ~ and used mass spectrometry to characterize the fraction of degradation products volatile above -70 ~ Typically, this was 20 percent of the volatiles and was stated to consist of almost entirely of isobutylene. About 10 percent of the volatiles were thought to be dimer and trimer. The remaining 70 percent of the volatile material was assumed to be higher oligomers, with an average length of 9 to 10 monomer units, Earlier, Wall [2] had reported that 78 percent of the volatile products consisted of monomer when the decomposition was carried out at 400 ~ Using thermogravimetry to measure rates of volatilization at various temperatures in the range 306 ~ to 326 ~ , Madorsky and Straus [3] determined the activation energy of the in vacuo thermal degradation to be 49 kcal/mol (200 k J/mole).Inoue et al. [4] reported an activation energy of initiation of 41 kcal/mole (170 k J/mole) and an average chain length of 30 for thermal degradation of PIBu above 280 ~ Slobodin and Matusevich [5] found the products of PIBu which had been decomposed thermally at 325 to 400 ~ to be 49 percent isobutylene, ~ 1 percent isobutene and isopentane, 17 percent C 8 hydrocarbons, 18 percent C12 hydrocarbons,

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“…3 As degradation proceeds, the initiation rate of degradation increases with decrease in the molecular weight because of increment of concentration of terminal double bond. As wellknown, 2 -4 both RP · and R, · formed in the random and/or end initiation 1 b regenerate frequently RP · by elementary reactions in the depropagation step.…”

Section: Effects Of Initiation On Radical Concentrationmentioning

confidence: 99%

“…The formation of these olefins could be reasonably explained by the reaction model consisting of the intramolecular hydrogen abstraction (back-biting) of RP · and R 1 • and the subsequent p scission at the inner position of the main chain. 3 The reactivities for abstraction of interest hydrogens (CH 2 and CH 3 ) are governed not by the steric hindrance-depending mechanism 1 b, 3 but by the bond energy-depending mechanism. The latter mechanism predicts that back-biting occurs predominantly at CH 2 rather than at CH 3 in the same manner as intermolecular hydrogen abstractions 4 In this paper, the effects of the physical factors such as pressure in the reaction vessel and the volume and molecular weight of the molten polymer matrix on the thermal degradation of polyisobutylene are examined and a degradation mechanism including diffusioncontrolled termination is proposed.…”

mentioning

confidence: 99%

Effects of Molecular Weight of Reaction Media on Formation of Volatile Oligomers by Thermal Degradation of Polyisobutylene

Sawaguchi

Senō

1996

Polym J

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ABSTRACT:For the thermal degradation ofpolyisobutylene, the effects of physical factors such as pressure in the reaction vessel and volume and molecular weight of the molten polymer matrix constituting the reaction media on the formation of the volatile oligomers were examined by a kinetic approach with measurements of composition ratios for terminal monoolefins [(TTD)P, (TVD)p, (TTD),, and (TVD) , do not depend on pressure and initial mass of sample, but depend on the initial molecular weight of sample. These values decrease clearly as the initial molecular weight decreases. It could be deduced that the decrease in molecular weight of the matrix decreases concentration ratio of two types of terminal macroradicals ([Rp · JI[R, · ]). According to the proposed kinetics of a chain mechanism including diffusion-controlled termination, a marked decrement of the radical concentration ratio suggests that the rate of termination increases with decrease in molecular weight of the matrix and that resulting decrement of kinetic chain length depresses the formation of the primary terminal macroradical (RP ·) in the depropagation step.,KEY WORDS Although some physical factors such as volume and molecular weight of molten polymers as a reaction media affect polymer reactions in the melt, la there is little information regarding this problem. We examined this effects from detailed structural and kinetic analyses of the products in a series of studies on the thermal degradation of polyisobutylene. One of the most remarkable features of the thermal degradation of mainchain-scission type of polymers such as polyisobutylene, polyethylene, polypropylene, polystyrene, and poly-(methyl methacrylate) is decrease in volume and molecular weight of the molten polymer matrix constituting the reaction media during degradation. In the previous papers, 2 we showed that the main products in the volatile oligomers formed by thermal degradation of polyisobutylene are four types of terminal monoolefins, 2 a as shown below: a terminal vinylidene double bond (TVD) type and a terminal trisubstituted double bond (TTD) type of olefins with a tert-butyl end (t-Bu) formed from a primary (p) terminal macroradical (Rp · ), and TVD and TTD type of olefins with an isopropyl end (i-Pr) formed from a tertiary (t) terminal macroradical (R 1 • ) CH 3 CH 3 CH 3 Each homologue consists of oligomers from dimers to dodecamers. The formation of these olefins could be reasonably explained by the reaction model consisting of the intramolecular hydrogen abstraction (back-biting) of RP · and R 1 • and the subsequent p scission at the inner position of the main chain. 3 The reactivities for abstraction of interest hydrogens (CH 2 and CH 3 ) are governed not by the steric hindrance-depending mechanism 1 b, 3 but by the bond energy-depending mechanism. The latter mechanism predicts that back-biting occurs predominantly at CH 2 rather than at CH 3 in the same manner as intermolecular hydrogen abstractions 4 of both RP · and R 1 ·, in conformity with the order of bond disso...

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Thermal decomposition products of polyisobutylene

Cited by 47 publications

References 5 publications

Effect of pressure on thermal degradation of polyethylene

Effect of pressure on thermal degradation of polyethylene

Thermal degradation of polyisobutylene studied using factor-jump thermogravimetry

Effects of Molecular Weight of Reaction Media on Formation of Volatile Oligomers by Thermal Degradation of Polyisobutylene

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