Poly pyrolysis yields

One aspect of the polymerization that is well established is the initiation step when di-p-xylylene is pyrolyzed. An alternate initiation mode involving the direct formation of the diradical LV from LIII by cleavage of only one of the two CH2—CH2 bonds is ruled out from experiments with monosubstituted di-p-xylylenes. When acetyl-di-p-xylylene is pyrolyzed and the pyrolysis vapor led through successive condensation surfaces at temperatures of 90 and 25°C, respectively, the result is the formation of two different polymers neither of which is poly(acetyl-di-p-xylylene). Pyrolysis yields acetyl-p-xylylene and p-xylylene... 

Copolymerization of Chloro- and Dichloro-/>-xylylene. Trichloro-di-p-xylylene (XVIII) was obtained by chlorination of di-p-xylylene with three molar equivalents of chlorine. Pyrolysis yielded monomers XV and XIX, which were condensed and polymerized on a 90 °C. surface. A quantitative yield of product was obtained. The product was transparent, tough, self-extinguishing, had a softening point above 280°C., and exhibited the correct elemental analysis for copolymer XX. Owing to the low solubility of the chlorinated poly-p-xylylenes, no attempts... 

Lehrle, R.S. and Williams, R.J., Thermal Degradation of Bacterial Poly(hydrox-ybutyric acid) Mechanism from the Dependence of Pyrolysis Yields on Sample Thickness, Macromolecules, 27, 3782, 1994. 

Table 3.5 Pyrolysis yields of poly(butyl acrylate)s ...

Pyrolysis of /7-xylene yields poly(/7-xylylene) [IUPAC poly(l,4-phenyleneethylene)] [Errede and Szwarc, 1958 Humphrey, 1984 Itoh, 2001 Lee, 1977-1978 Lee and... 

Poly(a-phenylethyl isocyanide), however, yields complex products distinguishable from monomer upon thermal degradation at 20 mm Hg (13). At 300° C a viscous condensate is produced which is free of isocyanide absorption in its infrared spectrum and appears very similar to the recently synthesized oligo-isocyanides, a,co-dihydrotri(a-phenylethyl isocyanide) and a,co-dihydrohexa(a-phenylethyl isocyanide) (15). Pyrolysis at 500° C produces an intense broad infrared absorption band in the range about 3300 cm-1, which is the range of associated N il bonds. Pyrolysates obtained at 700° C reveal nitrile absorption at 2270 cm"1, that becomes more intense in pyrolysates produced at temperatures up to 1300° C. A slow pyrolysis at 200-300° C is indicated for the study of primary structural changes in poly(a-phenylethyl isocyanide). Pyrolysates of poly(<7-... 

Pyrolysis of poly(methylacetylene) shows rather similar behaviour 528>, with mesi-tylene as the major product but substantial yields of methyl and proton-enriched products. Thermal decomposition of this polymer sets in at around 150 °C and the mechanism is postulated to involve chain scission followed by cyclization reactions and both electron-proton and electron-methyl exchanges. Pyrolysis of poly(phenyl-acetylene) has been reported to start at 270 °C in nitrogen 529). 

Figure 5. Variation in absolute yields of 2,3-dimethylthiophene, n-non-l-ene and 1,2-dimethylbenzene (/ig/mg kerogen) with depth for the Monterey Fm. kerogens. Yields determined from FID chromatograms after co-pyrolysis of the kerogens with known amounts of poly-/ -f-butylstyrene (Larter and Senftle, 44).

The acidic nature of the phosphorus compounds (24) alters the course of the pyrolysis of certain polymers. Gruntfest and Young (19) previously postulated that with poly (methyl methacrylate) an acid functions as a chain stopper or causes a primary alteration of the PMMA, such as crosslinking. They noted the formation of high yields of dimethyl... 

In 1947 Szwarc prepared a white polymeric material u by rapid flow pyrolysis of p-xylene under reduced pressure. On the basis of p-xylylene diiodide 2) detected in the reaction mixture of the pyrolysis products with iodine gas he proposed a formation 1,3) of p-xylylene(p-quinodimethane) (QM) in this pyrolysis. He claimed the polymeric material to be poly-p-xylylene(poly-QM)and proposed a mechanism 2) for the formation of poly-QM, involving thermal cleavage of carbon-hydrogen bonds of p-xylene to yield p-xylyl radicals which collide with each other to give p-xylene and QM through disproportionation. QM condenses and polymerizes to produce poly-QM. 

Synthesis from polyethylene glycol dibromides. Treatment of a poly (ethylene glycol) dibromide with Ba(OH)2 8H2O as a source of OH" and Ba followed by pyrolysis results in a crown ether. The Ba ion acts as a template. The present method requires only one building block (with one less oxygen than the crown ether formed). Highest yields (50%) are obtained with 18-crown-6. ... 

A potentially valuable characteristic of poly(ether-ketone-carborane)s is that they display enormously enhanced char-yields (up to 95% on pyrolysis in air), compared to the yields obtained from analogous all-aromatic polymers.7 This behaviour suggests that carborane-based polyketones such as 7 could eventually find application as fire-retardants and as precursor polymers for carbon-ceramic materials. 

Figure 16. Changes in product yields of catalytic cracking of heavy oil obtained by the pyrolysis of poly-ethylene using REY zeolite.

A plant operating according to the Hamburg University pyrolysis process was built at Ebenhausen, with a capacity of 5000 tonnes per year. The feasibility of converting poly-oleflns by pyrolysis was successfully demonstrated, with yields from PE/PP mixtures of typically 51% (m/m) gas, 42% (m/m) liquids and the balance unaccounted for. However, the gas to liquids ratio is very sensitive to pyrolysis temperature. Since gas and oil are the major pyrolysis products, economic viability crucially depends on the price of crude oil. Under present conditions, profitability and economic viability are unsatisfactory at this small scale of operation. 

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