Effect on thermal degradation

Crosslinking has no specific direct effect on thermal degradation crosslinks can be either weak points (e.g., tertiary carbons in polyester or anhydride-cured epoxies) or thermostable structural units (e.g., trisubstituted aromatic rings in phenolics, certain epoxies, or certain thermostable polymers). Indirect effects can be observed essentially above Tg crosslinking reduces free volume and thus decreases 02 diffusivity. It also prevents melting, which can be favorable in burning contexts. 

The thermal properties of Devonian shale are quite different from those of Green River oil shale. The associated pyrite in kerogen concentrate may contribute greatly to the effect on thermal degradation of Devonian gas-bearing shale. For the first time DSC was applied to determining thermal properties of Devonian shale as well as Green River oil shale. 

H. Ma, Z. Fang, and L. Tong. Preferential melt intercalation of clay in ABS/ brominated epoxy resin-antimony oxide (BER-AO) nanocomposites and its S5mergistic effect on thermal degradation and combustion behavior. Polymer Degradation and Stability, 91 (2006), 1972-1979. 

Chow, S.-Z. and Mukai, H.N. (1972). Effect of thermal degradation of cellulose on wood-polymer... 

M. Brebu, T. Bhaskar, K. Murai, A. Muto, Y. Sakata, and M.A. Uddin, The individual and cumulative effect of brominated flame retardant and polyvinylchloride (pvc) on thermal degradation of acrylonitrile-butadiene-styrene (ABS) copolymer, Chemosphere, 56(5) 433 440, August 2004. 

An extensive review of the literature to 1958 on thermal degradation of wood is given by Browne (5). Beall and Eickner (15) and Goldstein (4) add additional review information on this complex subject. Shafizadeh s (21) review of the pyrolysis and combustion chemistry of cellulose gives a basis for understanding these processes in wood and the effect of fire-retardant treatment on these processes. 

The effect of thermally degraded fructose and glucose on two azo dyes was considered in Chapter 9. 

Wang, Z., Han, E., and Ke, W. 2006. Effect of acrylic polymer and nanocomposite with nano-Si02 on thermal degradation and fire resistance of APP-DPER-MEL coating. Polymer Degradation and Stability 91(9) 1937—1947. 

Although solution blending has only been used at the lab scale at this time, compared with the in situ process, it may be more industrially friendly, particularly for the primary polymer producers who have operations, which can easily recover and recycle the solvent. High dilution is required and this may have an effect on the production of the PNs and the process is quite dependent on the individual polymer. Some polymers have many solvents from which to choose while others do not. A typical example is polystyrene, which can dissolve in a variety of solvents, so it is easy to find a solvent that is compatible with both the clay and the polymer. Polyolefins, on the other hand, require high boiling solvents and the high temperature may exert an effect of thermal degradation on the modifier. 

Inaba, A., Kashiwagi, T., and Brown, J. E. Effects of initial molecular weight on thermal degradation of polyfmethyl methacrylate) Part 1—Model 1. Polymer Degradation and Stability 1988 21 1. 

T. Bhaskar, T. Matsui, M. A. Uddin, J. Kaneko, A. Muto, and Y. Sakata, Effect of Sb203 in brominated heating impact polystyrene (HIPS-Br) on thermal degradation and debromination by iron oxide carbon composite catalyst (Fe-C), Appl. Catal. B. Env., 43, 229-241 (2003). 

Figure 8 The effects of thermal degradation on the photodegradation profile obtained during photostability testing.

Both thermal and photochemical processes take the form of a dehydrochlorination reaction which leads to discolouration as well as extensive changes in the internal structure of the polymer which has an unfavourable effect on the desirable electrical and mechanical properties. It has become apparent that considerable similarity exists between the two degradation processes and that it is neither easy nor desirable to make a vigorous distinction between the two. Information gained from e eriments on thermal degradation are often directly relevant to the analogous photochemical process. 

Polyanhydrides are a class of bioerodible polymers that have shown excellent characteristics as drug delivery carriers. The properties of these biomaterials can be tailored to obtain desirable controlled release characteristics. Extensive research in this promising area of biomaterials is the focus of this entry. In the first part of the entry, the chemical structures and synthesis methods of various polyanhydrides are discussed. This is followed by a discussion of the physical, chemical, and thermal properties of polyanhydrides and their effect on the degradation mechanism of these materials. Finally, a description of drug release applications from polyanhydride systems is presented, highlighting their potential in biomedical applications. 

It is generally accepted that thermal stability of polymer nanocomposites is higher than that of pristine polymers, and that this gain is explained by the presence of anisotropic clay layers hindering diffusion of volatile products through the nanocomposite material. It is important to note that the exfoliated nanocomposites, prepared and investigated in this work, had much lower gas permeability in comparison with that of pristine unfilled PE [12], Thus, the study of purely thermal degradation process of PE nanocomposite seemed to be of interest in terms of estimation of the nanoclay barrier effects on thermal stability of polyolefin/clay nanocomposites. 

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