Decomposition of polymers

Fig. 4.22 Apparent specific surface A(app) of carbons obtained from the decomposition of polymers, plotted against the carbonization temperature, (a) Polyfurfuryl carbons (b) dibenzanthrone carbons (c) polyvinylchloride carbons. O, A(app) estimated from CO2 isotherm at 195 K (a fCOj) = 17-0 A ) A. /f(app) estimated from N2 isotherm at 77 K = 16-2 A ). (Courtesy Marsh and Wynne Jones.)...

Eig. 6. Decomposition of polymers as a function of temperature during heating. A, polymethylene B, polytetrafluoroethylene C, silicone D, phenoHc resin ... 

For chemical recycling of plastics refuse, a cascade of cycled-spheres reactors was developed which combined separation and decomposition of polymer mixtures by stepwise pyrolysis at moderate temps. In low-temp, pyrolysis, mixtures of PVC, PS and PE or PS, polyamide-... 

Recycling to monomers, fuel oils or other valuable chemicals from the waste polymers has been attractive and sometimes the system has been commercially operated [1-4]. It has been understood that, in the thermal decomposition of polymers, the residence time distribution (RTD) of the vapor phase in the reactor has been one of the major factors in determining the products distribution and yield, since the products are usually generated as a vapor phase at a high temperature. The RTD of the vapor phase becomes more important in fluidized bed reactors where the residence time of the vapor phase is usually very short. The residence time of the vapor or gas phase has been controlled by generating a swirling flow motion in the reactor [5-8]. 

Figure 2. A Spectra of propene adsorbed on CoZSM-5 at increasing temperature B Spectra of NO adsorbed on CoZSM-5 before the contact with propene (a) and upon the formation and further decomposition of polymer (b).

For the reader who is interested in pursuing the mathematical details of CC, I recommend the papers of Smit and his co-workers (15) These researchers published early in the area of CC (16) and continue to contribute regularly to the field (17) Phillips has also been active in the field of CC, which he considers to be a subset of what he calls, multiplex chromatography (18). Some workers have used on-line correlation chromatography to study the thermal decomposition of polymers and compared the results against those using conventional injection procedures (19), while others have applied it to the study of gas-solid adsorption (20) ... 

It has been known for some time that lithium can be intercalated between the carbon layers in graphite by chemical reaction at a high temperature. Mori et al. (1989) have reported that lithium can be electrochemically intercalated into carbon formed by thermal decomposition to form LiCg. Sony has used the carbon from the thermal decomposition of polymers such as furfuryl alcohol resin. In Fig. 11.23, the discharge curve for a cylindrical cell with the dimensions (f) 20 mm x 50 mm is shown, where the current is 0.2 A. The energy density for a cutoff voltage of 3.7 V is 219 W h 1 which is about two times higher than that of Ni-Cd cells. The capacity loss with cycle number is only 30% after 1200 cycles. This is not a lithium battery in the spirit of those described in Section 11.2. 

Following Cahn s theory, more extended versions were proposed by Langer et al. [ O] and Binder et al. [ l] Recently, de Gennes [52], and Pincus [53] applied spinodal decomposition to polymer mixtures. Many of the recent experimental studies on spinodal decomposition of polymer mixtures deal with measuring characteristic scattering maxima with various scattering techniques [5A-60]. 

Why is the thermal decomposition of polymers of formaldehyde called unzipping ... 

Gas chromatography (GC) and mass spectrometry (MS) can be coupled to the TGA instrument for online identification of the evolved gases during heating pyrolysis-GC/MS is a popular technique for the evaluation of the mechanism and the kinetics of thermal decomposition of polymers and rubbers. Moreover, it allows a reliable detection and (semi)quantitative analysis of volatile additives present in an unknown polymer sample. 

The decomposition of polymer molecules in wastewater samples can also be achieved by a hybrid sensor, which consists of a consortium of microorganisms and hydrolases together. As an example, the BOD of lactose-containing wastewater was determined by a hybrid sensor consisting of cells of the yeast Lipomyces kononenkoae and of the enzyme /1-galactosidase [50, 69]. It is also possible to use a column containing immobilized enzymes, which is inserted in the measuring device (e.g., an FIA) before the biosensor [52, 70]. Such a combination of an enzyme column, which contains a-amylase and amy-... 

S.I. Stoliarov, P.R. Westmoreland, H. Zhang, R.E. Lyon, and M.R. Nyden, Molecular modeling of the thermal decomposition of polymers. In Fire and Polymers IV, Materials and Concepts for Hazard Prevention, C.A. Wilkie and G.L. Nelson (eds.), American Chemical Society, Washington, DC ACS... 

F.M. Esposito and Y. Alarie, Inhalation toxicity of carbon monoxide and hydrogen cyanide gases released during the thermal decomposition of polymers, Journal of Fire Sciences, 6, 195-242, 1988. 

Overview articles on the formation and decomposition of polymer peroxides [35, 36, 37] confirm the formation of weak bonds during the polymer synthesis following from various experimental data. 

Beyler CL and Hirschler MM, "Thermal Decomposition of Polymers", in DeNenno PJ (Ed), "SFPE Handbook of Fire Protection Engineering", NFPA, Quincy, Ma, 3rd Ed, 2002, Chap. 7. 

In general, many mechanisms are available for thermal decomposition of polymers used for binders in ceramics. These general mechanisms are outlined in Figures 15.1 and 15.2. One of these main thermal... 

This same reaction sequence can be used to describe the thermal decomposition of polymers under reducing conditions. In this case, the value of n is equal to 0 and h is usually set equal to 1.0 in the generalized reaction. Under these conditions, the mass transfer is limited to the removal of the volatiles from the porous green body. This mass transfer can be limited by the pore diffusion or the boundary layer. We still must consider that the surface reaction or the steps of heat transfer in the boundary layer or heat conduction in the porous body could also be rate controlling in this case of the thermal decomposition of polymers under reducing conditions. 

Accounting for these rate determining steps the kinetics of binder burnout can be established for simple decompositions of polymers, such as depolymerization and the oxidation of carbon. For polymers with... 

J. Yang, R. Mirand and C. Roy, Using the DTG cnrve fitting method to determine the apparent kinetic parameters of thermal decomposition of polymers. Polymer Degradation and Stability, 73, 455-461 (2001). 

Z. Czegeny, E. Jakab, M. Blazso, Thermal decomposition of Polymer mixtures containing Poly(vinyl chloride), Macromol. Mater. Eng., 287, 277-284 (2002). 

Polysilane derivatives constitute a new class of radiation-sensitive materials with interesting physical and electronic properties. The photochemical decomposition of polymers containing disilanyl units seems adequately explained by silicon-silicon bond homolysis and subsequent radical reactions. The solution photochemistry of longer silicon catenates results in the extrusion of substituted monomeric silylenes, as well as the formation of silyl radicals produced by chain homolysis. Recent studies indicating that the... 

---