Polyurethane Pyrolysis

Figure 3.4 CI-MS survey scan of polyurethane (pyrolysis region, 200-300 °C). Reprinted with permission from R.P. Lattimer, Rubber Chemistry and Technology, 1995, 68, 783. 1995, ACS Rubber Division [27])...

Polyurethane Pyrolysis tandem MS - Methylene diisocyanate, 1.4- butane diol, 1.4- cyclohexane dimethanol, low molecular weight oligomers of hydroxyl terminated tetramethylene glycol adipate Cleavage of urethane link via NH transfer resulting in these products [36]... 

Ammonia is used in the fibers and plastic industry as the source of nitrogen for the production of caprolactam, the monomer for nylon 6. Oxidation of propylene with ammonia gives acrylonitrile (qv), used for the manufacture of acryHc fibers, resins, and elastomers. Hexamethylenetetramine (HMTA), produced from ammonia and formaldehyde, is used in the manufacture of phenoHc thermosetting resins (see Phenolic resins). Toluene 2,4-cHisocyanate (TDI), employed in the production of polyurethane foam, indirectly consumes ammonia because nitric acid is a raw material in the TDI manufacturing process (see Amines Isocyanates). Urea, which is produced from ammonia, is used in the manufacture of urea—formaldehyde synthetic resins (see Amino resins). Melamine is produced by polymerization of dicyanodiamine and high pressure, high temperature pyrolysis of urea, both in the presence of ammonia (see Cyanamides). 

Synthetic Resins. Various polymers and resins are utilized to produce some specialty carbon products such as glassy carbon or carbon foam and as treatments for carbon products. Typical resins include phenoHcs, furan-based polymers, and polyurethanes. These materials give good yields of carbon on pyrolysis and generally carbonize directly from the thermoset polymer state. Because they form Httle or no mesophase, the ultimate carbon end product is nongraphitizing. 

Glassy, or vitreous, carbon is a black, shiny, dense, brittle material with a vitreous or glasslike appearance (10,11). It is produced by the controUed pyrolysis of thermosetting resins phenol—formaldehyde and polyurethanes are among the most common precursors. Unlike conventional artificial graphites, glassy carbon has no filler material. The Hquid resin itself becomes the binder. 

PURs. See Polyurethanes (PUs, PURs) Pyrex hydrolysis reactor, hydrolysis of polyurethane in, 573 Pyrolysis, 208... 

Most dyes, including sulfonated azo dyes, are nonvolatile or thermally unstable, and therefore are not amenable to GC or gas-phase ionisation processes. Therefore, GC-MS techniques cannot be used. GC-MS and TGA were applied for the identification of acrylated polyurethanes in coatings on optical fibres [295]. Although GC-MS is not suited for the analysis of polymers, the technique can be used for the study of the products of pyrolysis in air, e.g. related to smoke behaviour of CPVC/ABS and PVC/ABS blends [263],... 

Levin, B.C., A summary of the NBS litterature Reviews on the chemical nature and toxicity of the pyrolysis and combustion from seven plastics acrylonitrite-butadien-styrenes (ABS), nylons, polyesters, polyetylenes, polysterenes, poly(vinyl-chlorides) and rigid polyurethane foams, KB SIR 85-3267, 1986... 

Littorin, M., Truedsson, L., Welinder, H.. Skarping, G, Martensson, U. Sjohohn, A.G (1994) Acute respiratory disorder, rhinoconjimctivitis and fever associated with the pyrolysis of polyurethane derived from diphenylmethane diisocyanate. Scand. J. Work Environ. Health, 20,216-222... 

Recycling. The methods proposed for the recycling of polyurethanes include pyrolysis, hydrolysis, and glycolysis. Regrind from polyurethane RIM elastomers is used as filler in some RIM as well as compression molding applications. The RIM chips are also used in combination with rubber chips in the construction of athletic fields, tennis courts, and pavement of working roads of golf courses. 

R.A. Beyer, Molecular Beam Sampling Mass Spectrometry of High Heating Rate Pyrolysis. Description of Data Acquisition System and Pyrolysis of HMX in a Polyurethane Binder ,... 

Old polyurethane on rims may be removed either on a lathe, by solvent attack, or by freezing in liquid nitrogen. For more complex shapes, the reinforcing may be recovered by the above methods as well as by pyrolysis in a specially designed chamber, where the material is heated in the absence of air to above the decomposition temperature of the polyurethane. The fumes are then burned using special after-burners. 

Bilbao, R., Mastral, J.F., Ceamanos, 1, and Aldea, M.E., Kinetics of the thermal decomposition of polyurethane foams in nitrogen and air atmospheres, Journal of Analytical and Applied Pyrolysis, 37 (1), 69-82, 1996. 

PTV PU PVA PVAC PVAL PVC PVDC PVDF PVE PVF PXRD py Py PY Py-GC-MS pyr pyrr pz programmed-temperature vaporizer polyurethane poly (vinyl alcohol) poly(vinyl acetate) poly (vinyl alcohol) poly (vinyl chloride) poly(vinylidene dichloride) poly(vinylidene difluoride) poly (vinyl ether) poly(vinyl fluoride) powder X-ray diffraction pyridine (ligand) pyridine pyramidal (coordination compounds) pyrolysis-gas chromatography-mass spectrometry pyrazine (ligand) pyrrolidine (ligand) pyrazole (ligand)... 

Research on the pyrolysis of thermoset plastics is less common than thermoplastic pyrolysis research. Thermosets are most often used in composite materials which contain many different components, mainly fibre reinforcement, fillers and the thermoset or polymer, which is the matrix or continuous phase. There has been interest in the application of the technology of pyrolysis to recycle composite plastics [25, 26]. Product yields of gas, oil/wax and char are complicated and misleading because of the wide variety of formulations used in the production of the composite. For example, a high amount of filler and fibre reinforcement results in a high solid residue and inevitably a reduced gas and oiFwax yield. Similarly, in many cases, the polymeric resin is a mixture of different thermosets and thermoplastics and for real-world samples, the formulation is proprietary information. Table 11.4 shows the product yield for the pyrolysis of polyurethane, polyester, polyamide and polycarbonate in a fluidized-bed pyrolysis reactor [9]. 

D. A. Takamoto and M. A. Petreich, Effect of heterogeneous secondary pyrolysis reactions on the thermal decomposition of polyurethane scrap. Ind.Eng.Chem.Res., 33, 3004-3009, (1994). 

N. Grittner, W. Kaminsky and G. J. ObsL Fluid bed pyrolysis of anhydride-hardened epoxy resins and polyether-polyurethane by the Hamburg process. J. Anal. Appl. 

Pyrolysis could be considered as an nnsnitable way of recycling for polyurethanes because the liquid product is extremely viscous and can solidify over time [41]. The main reason of the severe instability of polynrethane pyrolysate is the reactivity of the diisocyanate component, the regained polynrethane-forming reactant. The other component of thermoplastic polyurethanes is either a polyether or a polyester which could lead to stable pyrolysis liquid if the reactive diisocyanate is eliminated from it. 

R. P. Lattimer, M. J. Polce and C. Wesdemiotis, MALDl-MS analysis of pyrolysis products from a segmented polyurethane, J. Anal. Appl. PyroL, 48, 1-15 (1998). 

For shredder light fractions, a mixture of polyolefins and polyurethanes containing as well as polyamides, PVC, polystyrene and blends, Wanzl et al. [23, 24] and Basel [25] have shown for the treatment of the pyrolysis gases from rotary kiln pyrolysis that by using dolomite beds at 500°C and a residence time of 20 s, chlorine content can be reduced from 1000 ppm to below the detection limit of 1 ppm. 

Polymers are used frequently in paints and varnishes. These materials are usually filled with opaque materials and are difficult to separate or analyze by other procedures. Pyrolysis can be used to identify the nature of the paint, to measure quantitatively residual monomers, for quality control, and to examine additives [5, 13, 14]. Paints may contain a variety of polymers and copolymers such as vinyl derivatives, polyurethanes, phthalate polyesters, etc. Varnishes may contain various copolymers, siloxanes, etc. and can have a complex composition. This composition can be successfully analyzed using analytical pyrolysis. For example, the composition of a coating material consisting of the terpolymer poly(2-hydroxyethyl methacrylate-co-butyl acrylate-co-ethyl methacrylate) crosslinked with butoxy melamine resin has been analyzed with excellent results based on various monomer ratios resulting from pyrolysis at 590° C [15]. 

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