Thermo-Oxidative Decomposition

This term is used for any additives that allow a polymer to retard a flame, or for any polymer that shows the ability to slow fire growth when ignited. It does not mean noncombustible or ignition resistant—these are very different terms and should not be used to describe a flame-retardant material. A material that is truly noncombustible or ignition resistant either cannot be combusted (no thermo-oxidative decomposition can occur) or cannot be ignited with a particular size... 

Fichera MA, Braun U, Schartel B, Sturm H, Knoll U, Jager C, Solid-state NMR investigations of the pyrolysis and thermo-oxidative decomposition products of a polystyrene/red phosphorus/magnesium hydroxide system. J. Anal. Appl. Pyrolysis 2007 78 378-386. 

Kasprzycka-Guttman, T., Jarosz-Jarszweska, M., and Litwinienko, G. 1995. Specific Heats and Kinetic Parameters of Thermo-Oxidative Decomposition of Peanut Oil. Thermochim. Acta, 250,197-205. 

Following a related approach, Castelvetro et al. reported the formation and properties of hybrid latex films resulting from the coalescence of low 7 poly(BA-co-MMA-co-MPTMS) terpolymer latex particles coated by a silica shell [78], The latex was synthesized at neutral pH by semi-continuous emulsion polymerization under starved-feed conditions in order to protect the MPTMS monomer from premature hydrolysis and condensation reactions. A substantial amount of free silanols were therefore available for further reaction with the silica precursor. In order to avoid the formation of a densely crosslinked silica network around the latex core, which may significantly alter film formation, the pH was kept at around 2 (at this pH, hydrolysis is promoted and condensation is significantly retarded). TEM and AFM studies of the nanocomposite film indicated that the silica shell formed a continuous percolating network throughout the polymer matrix. A porous film of interconnected hollow silica spheres was next elaborated by thermo-oxidative decomposition of the organic phase. 

The study of degradation processes of polymers and organic materials is a fundamental topic both from academic and industrial point of view and it can be expected that thermal and thermo-oxidative decomposition mechanisms are reasonably well established. [20,3 8] These complex reactions proceed via a typical free-radical chain as outlined in scheme 2. 

PPQ films discolor on heating, but retain their transparency and the major parts of their mechanical properties. To date, PPQs have been tested for application as high-temperature-resistant adhesives and as matrices for bonding materials. In such high-temperature applications, a postcuring must be applied whereby cross-linking occurs as a result of thermal or thermo-oxidative decomposition. 

Introduction DMB leads to significant changes in processes thermo-oxidative decomposition the weight loss for copolymers is registered at lower temperatures (Fig. 2) and proceeds more intensively (Fig. 3). With the increase of temperature up to 300°C, as can be seen, the presence of DMB causes the reduction of the speed of weight loss. The speed of the smaller, more content maleic links. The endothermic peak of more than offset by a comparison with PVA, however, extends to a wider temperature field (200-350°C). 

PF foams offer to the construction industry a useful combination of physical and flammability characteristics. They generate low levels of smoke in most fire tests. It was reported that a cupric complex of a macro heterocyclic compound is an effective stabiliser for thermo-oxidative decomposition of PF foams above 200 °C. An amount of 0.25-5.0 pph permits significant decrease of ignitability [178]. 

Unit Thermo-oxidative decomposition Thermal decomposition ... 

Experiments with other derivatives indicate that salts of benzoxazolone derivatives raise the thermo-oxidative decomposition temperature by about 15°C, depending on the nature of the metal of the salt and the presence of substituents in their molecules. Sodium and cobalt salts raise the level by about 2()°C. The stabilizing action of sodium and cobalt salts seems to be due to inhibition of free radical breakdown of the PVC by acceptance of the HCl formed, and replacement of the labile chlorine atom of PVC by benzoxazolone groups. 

In the area of polymers, the action and effect of organoboron compounds on the thermo-oxidative decomposition of poly(vinyl chloride) has been investigated as have heat-resistant borazole copolymers and adhesives based on these copolymers/ ... 

A. Products of Thermal and Thermo-Oxidative Decomposition and Combustion... 

The qualitative and quantitative determination of the thermal and thermo-oxidative decomposition and combustion products advances closely with the development of high-performance investigation techniques. Early on, only the main products or classes of compounds were studied, whereas recently, special importance has been given to the evidence of products appearing as traces, since these might cause serious problems both for human life (by their toxicity, especially in incomplete combustion) and for the purification of the products obtained from polymer waste pyrolysis (or incineration), applied for their recovery as high-grade materials. 

During thermal and thermo-oxidative decomposition, the nonvolatile material formed presents three types of unsaturation vinyl (R—CH=CH,), trans-vinylene (R — CH = CH — R ), and vinylidene [229]... 

Most products of thermal decomposition appear in the presence of oxygen (thermo-oxidative decomposition) too besides, a great number of oxygen containing compounds are present (Fig. 14 and Table 7). Although various aldehydes, ketones, and other oxygenated species are formed at low temperatures, these... 

In the composition of the combustion products, most products of thermal and thermo-oxidative decomposition appear in very low concentrations. Their composition depends on the mode of operation, e.g., in closed or open space, flameless or flame combustion, oxygen concentration, etc. The major products of combustion are distinguished by higher concentrations of the thermally stable compounds (CO2, H2O, CO, low molecular weight compounds, aromatics, etc.) and also by some toxic products. The apparent lethal concentrations (ALC50, 30 min exposure period) of pyrolysis products of polyolefins is about 11.8 mg, which indicates that they are not unusual or extremely toxic [205, 222, 232]. 

Generally, it is more difficult for oxygen to reach the burning surface during vigorous combustion than under the mild conditions of thermo-oxidative decomposition [253]. 

If in the first stage of thermo-oxidative decomposition the kinetic treatment for thermal degradation (Sec. E) can be applied, the kinetics of burning is very complex, as kinetics of both thermal and thermooxidative decomposition must be included along with the equations of mass and heat transfer [303]. 

Both thermal and thermo-oxidative decomposition of polyolefins are characterized by a set of kinetic parameters. 

The activation energies for thermo-oxidative decomposition are smaller than those for thermal decomposition. 

Table 2.1 Activation energy of sol and gel in thermal decomposition and thermo-oxidative decomposition ...

Igarashi and co-workers [1] studied the thermo-oxidative decomposition of polyoxymethylene in air hy thermogravimetric analysis (TGA) and infrared (IR) spectroscopy. Polyoxymethylene (POM) and acetylated polyoxymethylene (POMAc) were included in this study. In the presence of air, TGA-derived curves showed two peaks for each material (Figure 3.1). 

Figure 5.10 Experimental thermogravimetric and DTG curves (—) and stimulated individual (—) and total (—) DTG curves for thermo-oxidative decomposition of (a) iPP, (b) PA6, and (c) EPDM. au = arbitrary units Reproduced with permission from R.N. Darie, M. Brebu, C. Vasile and K. Kozlowski, Polymer Degradation and Stability, 2003, 80, 3, 551. 2003, Elsevier [25]...

Recent work conducted by Martin [6] has shown that zinc polyphosphates are important intermediate reaction products in the tribochemical reaction of ZDDP. ZDDP decomposition is thought to be through complex chemistry which can be either thermal, catal)dic or oxidative. In this case Martin believes that ZDDP undergoes mainly thermo-oxidative decomposition prior to friction, when the lubricant is heated above 100°C. 

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