Polycarbonate, thermal decomposition

Polyesterurethanes, polycarbonate and silicone rubbers have been studied by TG-Tenax-FTIR/MS. The degradation of polyesterurethanes yields C02, water, tetrahydrofurans, cyclopentanone, dicarbonic acid, and aliphatic diols and esters. The thermal decomposition of silicone rubbers leads to the formation of polychlorinated biphenyls which are produced in small amounts and can be observed in the mass spectrometer [86]. 

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. 

Volatile production occurs from polycarbonate by entirely thermal decomposition between 450 and 550°C yielding about 25% solid residue as well. The pyrogram of the most common aromatic polycarbonate, poly(bisphenol A carbonate) is displayed in Figure 12.10. Alkylphenols and phenol are the main constituents of the boiling range 180-250°C and... 

In addition to copolymers, various blends containing polyalkylstyrenes are used in practice. One such polymer is poly(4-methoxystyrene) 1/1 w/w blend bisphenol A polycarbonate. The thermal decomposition of this polymer when heated from ambient to 500° C generates CO2, 4-methoxystyrene, a-methyl-4-methoxystyrene, p-cresol and small amounts of other phenols, poly (4-methoxystyrene), dimer and trimer with vinylidene and saturated ends, polycarbonate cyclic dimer and chain fragments, bisphenol A, etc. [94]. 

Table 11.1.1. Summary regarding literature information on thermal decomposition of several polycarbonates [13].

Stoliarov, S.I. Westmoreland, P.R. Mechanism of thermal decomposition of bisphenol-C polycarbonate nature of its fire resistance. International Aircraft Fire Cabin Safety Research Conference. Atlantic City, NJ, 2001. 

Condensation polymers can be regarded as a sequence of monomer units containing fxmctional groups immobilized into the polymer structure. Their decomposition pathways will often be dominated by the polarity and by the reactivity of the fxmctional groups within their structure, and their thermal decomposition reactions will be ionic and selective, rather than radical and imselective. Such are the thermal degradation processes occurring in polyesters, polyamides, polycarbonates, polyurethanes, polyureas, and in several other cases. ... 

Montaudo, G., Puglisi, C., Rapisardi, R., and Samp>eri, E, Eurther Studies on the Thermal Decomposition Processes in Polycarbonates, Polym. Deg. Stab, 31, 229, 1991. 

Puglisi, C., Sturiale, L., and Montaudo, G., Thermal Decomposition Processes in Aromatic Polycarbonates Investigated by Mass Spectrometry, Macromolecules, 32, 2194, 1999. 

Polycarbonate possesses high mechanical strength, high thermal stability, transparency, good dielectric properties, thanks to which it is finding wide use in various branches of industry. It was shown in [22] that the thermal decomposition of polycarbonate, analogous to certain polyarylates, begins at temperatures above 400°C and is accompanied... 

Cox and co-workers [179] analysed PS/polyvinyl methyl ether blends by coincidence counting ToF mass spectrometry. This technique gave information on the chemical and spatial relationships between secondary ions. Thompson [180] carried out a quantitative surface analysis of organic polymer blends (e.g., miscible polycarbonate/PS blends) using ToF-SIMS. Lin and co-workers [181] used supersonic beam/multiphoton ionisation/ToF mass spectrometry to analyse photoablation products resulting from styrene-containing polymers snch as styrene-bntadiene, ABS, and PS foams. Photoablation products were examined by snpersonic beam spectrometry and the results were compared with those obtained by thermal decomposition. 

Supersonic jet spectrometry of the chemical species resulting from the thermal decomposition of polycarbonate at temperatures up to 400 C showed that p-cresol is the... 

Yoshioka, T. Sugawara, K. Mizoguchi, T. Okuwaki, A. Chemical Recycling of Polycarbonate to Raw Materials by Thermal Decomposition with Calcium Hydroxide/Steam. Chem. Lett. 2005,34,282-283. 

The diffusion coefficient required to account for penetration of about 500 A is of the order of 10 cm /sec. (for a 200 s. bake). For small molecules (such as the monomeric resist components) this is a quite reasonable number, either above or below 7 (cf. measurements on camphorquinone in polycarbonate 18), which are in the range of 10 — 10 above Tg and 10 — 10 below). Tg of PVA is 85C (29). The situation is less clear with polymer diffusion. PPSQ apparently does not have a distinct Tg (20), but remains assy up to its thermal decomposition temperature (this report is for high material). Wang, et al., ( ) obtained diffusion coefficients of 10 cmVsec for high Af poly(but methacrylate) in latex particles, at temperatures well above Tg. It is possible that the low Af, siloxanes used here diffuse at substantially higher rates. Thus the postulated diffusion is plausible albeit not assured. 

The subsequent thermal processes201 give rise to diffusion of the polycarbonate substrate into the dye layer, decomposition of the dye, and mechanical deformation of the film due to thermal contraction. Each of these processes can contribute to a reduction in the optical path length of the low-intensity readout beam. The optics within the detector are designed such that phase differences due to the optical path length differences cause the light intensity falling on the detector to be reduced when the beam passes over a recorded mark .196... 

The degradation and combustion behavior of polycarbonate/POSS hybrid system has been reported recently.48 Different loading contents of trisilanolphenyl-POSS (TPOSS) were melt blended with polycarbonate matrix (PC). The data shown in Table 8.4 indicate that no improvement in thermal stability parameters (i.e., onset decomposition temperature and peak decomposition temperature) was observed compared to the neat polycarbonate. The thermo-oxidative degradation process of the hybrid system proved to be a complicated process, which includes hydrolysis/alcoholysis of the carbonate linkage, free radical oxidative chain degradation, reformation, and branching and cross-linking reactions. 

In a previous paper (1), phase segregation by spinodal decomposition in mixtures of polyethylene terephthalate and polyhydroxybenzoic acid copolymer (PET-PHB) and polycarbonate (PC) has been investigated. It was shown that thermally induced phase segregation takes place above the Tg of PC and exhibits a lower critical solution temperature (LCST). However, the phase separated domains do not grow until the temperature exceeds 255°C. Some disclinations developed within the liquid crystal rich regions. Even in the pure PET-PHB component, four dark brushes with negative sense of disclinations form around 240°C, indicating the presence of nematic liquid crystals. Paci and coworkers (2) claimed that a smectic-nematic transition exists near 270°C in this liquid crystalline copolyester. 

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