Nylons pyrolysis products

Conversion of polymers and biomass to chemical intermediates and monomers by using subcritical and supercritical water as the reaction solvent is probable. Reactions of cellulose in supercritical water are rapid (< 50 ms) and proceed to 100% conversion with no char formation. This shows a remarkable increase in hydrolysis products and lower pyrolysis products when compared with reactions in subcritical water. There is a jump in the reaction rate of cellulose at the critical temperature of water. If the methods used for cellulose are applied to synthetic polymers, such as PET, nylon or others, high liquid yields can be achieved although the reactions require about 10 min for complete conversion. The reason is the heterogeneous nature of the reaction system (Arai, 1998). 

Another case may occur when primary pyrolysis products quickly react among themselves, in the condensed phase, so that they are detected together with the products of further reaction. The latter situation occurs in the pyrolysis of Nylon 6,6 (Ny66), where a specific structural effect due to the adipic acid unit is responsible for the formation of very reactive pyrolysis compounds. ... 

The Cl mass spectrum of the pyrolysis products from Nylon 66, taken at 400°C (Figure 5.15), shows the presence of intense protonated molecular ions, which are identified in Table 5.2. 

Figure 5.8 shows the pyrogram of (a) nylon 6 and (b) nylon 6/6 observed by nsing a glass capillary separation colunm. The main pyrolysis products in (a) are 8-caprolactam" " and small amounts of nitriles (MN and MN(A)). Polylactams consisting of relatively short methylene chains, such as nylon 4 and 6, tend to regenerate the associated monomeric lactame upon heating. 

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). 

Pyrolysis produces three principal products - pyrolytic gas, oil, and char. Char is a fine particulate composed of carbon black, ash, and other inorganic materials, such as zinc oxide, carbonates, and silicates. Other by-products of pyrolysis may include steel (from steel-belted radial tires), rayon, cotton, or nylon fibers from tire cords, depending on the type of tire used. 

Electrical and electronic devices are made utilizing several various types of plastic materials, thus when discarded their waste is difficult to recycle. The plastics employed in housing and other appliances are more or less homogeneous materials (among others PP, PVC, PS, HIPS, ABS, SAN, Nylon 6,6, the pyrolysis liquids of which have been discussed above). However, metals are embedded in printed circuit boards, switches, junctions and insulated wires, moreover these parts contain fire retardants in addition to support and filler materials. Pyrolysis is a suitable way to remove plastics smoothly from embedded metals in electrical and electronic waste (EEW), in addition the thermal decomposition products of the plastics may serve as feedstock or fuel. PVC, PBT, Nylon 6,6, polycarbonate (PC), polyphenylene ether (PPO), epoxy and phenolic resins occur in these metal-containing parts of EEW. 

A typical analysis of L. fendleri seed oil showed the presence of 16 0 (1%), 18 0 (2%), 18 1 (15%), 18 2 (7%), 18 3 (14%), lesquerolic (54%), and auricolic (4%) acids. As lesquerolic acid is the C20 homologue of ricinoleic with the same p-hydroxy alkene unit, it undergoes similar chemical reactions but produces (some) different products. For example, pyrolysis should give heptanal and 13-tri-decenoic acid (in place of 11-undecenoic acid). This could be converted to 13-ami-notridecanoic acid, the monomer required to make nylon-13. Similarly, alkali-fusion will give 2-octanol and dodecanedioic acid in place of decanedioic (sebacic) acid. This C12 dibasic acid is aheady available from petrochemical products and has a number of applications. A recent account of the status of this oil is available (126). 

The chemistry of synthetic jasmine materials was given an enormous boost in the 1930s when Nylon 66 was launched as a product. Nylon 66 is a polyamide prepared using adipoyl chloride and hexamethylenetetramine as monomers. The 66 in the name refers to the fact that there are 6 carbons in each type of unit that lies between the amide links in the polymer chain. Thus, adipic acid is the key feedstock for Nylon 66 and the introduction of the latter meant that the former became a basic chemical commodity. Pyrolysis of the calcium or barium salt of adipic acid produces cyclopentanone, and so the availability of large quantities of the acid meant that the ketone could also be prepared at low cost. 

Figure 5.16 reports the CID product ions mass spectrum of the ion at m/z 209 evolving from the pyrolysis of Nylon 6,6, which appear identical to the spectrum of the authentic cyclic compound with the same mass. ... 

Some plasticised plastics products (e.g., PVC or nylon 11) will need to be extracted with a solvent (e.g., methanol) first to remove the plasticiser. Products that are filled (e.g., polypropylene/talc kettle bodies) will require a pyrolysis technique where a pyrolysis condensates infrared library, such as the one pubhshed by Rapra Technology, needs to be available. 

Products obtained by pyrolysis of other polymers is reviewed in Table 4.5. Some specific applications of the chromatography-MS technique to various types of polymers include the following PE [34,35], poly(l-octene) [29], poly(l-decene) [29], poly(l-dodecene) [29], CPE [36], polyolefins [37, 38], acrylic acid-methacrylic acid copolymers [39, 40], polyacrylate [41], nitrile rubber [42], natural rubbers [43, 44], chlorinated natural rubber [45, 46], polychloroprene [47], PVC [48-50], polysilicones [51, 52, 53], polycarbonates [54], styrene-isoprene copolymers [55], substituted olystyrene [56], PP carbonate [57], ethylene-vinyl acetate [58], Nylon 66 [59], polyisopropenyl cyclohexane-a-methyl styrene copolymers [60], cresol-novolac epoxy resins [61], polymeric flame retardants [62], poly(4-N-alkyl styrenes) [63], polyvinyl pyrrolidone [64], polybutyl-cyanoacrylate [65], polysulfides [66], poly(diethyl-2-methacryl-oxy) ethyl phosphate [67, 68], polyetherimide [69], bisphenol-A [70], polybutadiene [71], polyacenaphthalene [72], poly(l-lactide) [73], polyesterimide [74], polyphenylene triazine [75], poly-4-N-vinyl pyridine [76], diglycidylether-bisphenol-A epoxy resins [77], polyvinylidene chloride [78] and poly-p-chloromethyl styrene [79]. 

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