Thermal-Oxidative Degradation

Methylphenol is converted to 6-/ f2 -butyl-2-methylphenol [2219-82-1] by alkylation with isobutylene under aluminum catalysis. A number of phenoHc anti-oxidants used to stabilize mbber and plastics against thermal oxidative degradation are based on this compound. The condensation of 6-/ f2 -butyl-2-methylphenol with formaldehyde yields 4,4 -methylenebis(2-methyl-6-/ f2 butylphenol) [96-65-17, reaction with sulfur dichloride yields 4,4 -thiobis(2-methyl-6-/ f2 butylphenol) [96-66-2] and reaction with methyl acrylate under base catalysis yields the corresponding hydrocinnamate. Transesterification of the hydrocinnamate with triethylene glycol yields triethylene glycol-bis[3-(3-/ f2 -butyl-5-methyl-4-hydroxyphenyl)propionate] [36443-68-2] (39). 2-Methylphenol is also a component of cresyHc acids, blends of phenol, cresols, and xylenols. CresyHc acids are used as solvents in a number of coating appHcations (see Table 3). 

Stabilizers. Antioxidants provide protection against UV light and thermal oxidative degradation. Hindered phenols are the most common nonstaining antioxidants. For SBR latices, two additional type of stabilizers must be used. 

CL must be very carefully purified to exclude small concentrations of (1) ferric ions which would catalyze die thermal oxidative degradation of polycaprolactam and (2) aldehydes and ketones which would markedly increase oxidizability of CL. The impurities in CL may retard die rate of CL polymerization as well as having a harmful effect on die properties of die polymer fiber. In die vacuum depolymerization of nylon-6, a catalyst must be used because in die absence of a catalyst by-products such as cyclic olefins and nitrides may form, which affects the quality of die CL obtained.1... 

These results are quite different from others which have been reported in the literature concerning the high temperature (>600° C) thermal and thermal oxidative degradation of DBDPO, in which >90% degradation was reported (28). We confirmed that temperature was the principal cause for these different observations, by reproducing the 600° C isothermal pyrolysis of DBDPO in which less than 10% unreactive DBDPO was recovered. 

W. Zhao, T. Cao, and J.M. White, On the origin of green emission in polyfluorene polymers the roles of thermal oxidation degradation and crosslinking, Adv. Fund. Mater., 14 783-790, 2004. 

The behaviour of chain-length distribution is non-characteristic during thermal-oxidative degradation of isotropic PP films the degradation shifts towards decrease in molecular mass, while during oxidation in deformed films it shifts towards increase in molecular mass. It means that with oxidation in isotropic samples in the induction period the destruction of molecules prevails. On the other hand, with oxidation in deformed samples attachement and cross-linking dominate. 

Reaction 9 Thermal Oxidative Degradation - Hydroperoxide Formation [105]... 

In general, the degradation of PET is characterized by a loss in molecular weight, a loss in weight in the case of thermal and thermal oxidative degradation, and an increase in the carboxyl end groups. This is usually accompanied by the material first turning yellow, then brown and finally black [17]. 

Thermal-oxidative degradation is an additional reason for yam breaks commonly observed during polymer processing as a consequence of leaks in the equipment. Frequent testing of tightness is therefore an important part of production... 

An easy method for investigating the thermal-oxidative degradation of PET is differential thermal analysis (DTA), which indicates thermal degradation by the appearance of an exothermic peak in the range of the melting temperature. This approach also can be used to assess the efficiency of stabilizers [40],... 

B. M. Ginzburg, L. A. Shibaev, V. L. Ugolkov, Effect of fullerene C60 on thermal oxidative degradation of polymethyl methacrylate prepared by radical polymerization, Russian Journal of Applied Chemistry, vol. 74, pp. 1329-1337, 2001. 

MMBS modifiers a have poor resistance to thermal oxidative degradation. This poor resistance may manifest itself most strongly during such procedures as isolation and oven drying. The least severe manifestation is slight discoloration, while dryer fires are an extreme, though not uncommon, consequence of failure to stabilize MMBS modifiers (12). 

Polysulfone Plastics. These plastics which were commercialized by Union Carbide are actually aromatic polyethers containing periodic sulfone groups which provide additional resonance stabilization. They have good mechanical properties, creep resistance, and dimensional stability but their outstanding quality is their high heat distortion temperature (345°F.) and resistance to thermal oxidative degradation. Limitations are difficult thermoplastic processability, amber color, and sensitivity to organic solvents. 

In addition to acting as photostabilizers for polypropylene, nickel complexes also inhibit their direct thermal oxidative degradation by molecular oxygen. The salicylate complex (26), thought to be square planar, was more effective than the analogous cobalt(II) and copper(II) complexes.83 Iron(III) and chromium(II) analogues were almost inactive. Complexes (25) and (27) were roughly... 

Han S, Kim C, Kwon D (1997) Thermal/oxidative degradation and stabilization of polyethylene glycol. Polymer 38(2) 317-323... 

Thermal Oxidative Degradation of Coal as a Route to Sulfur Functionality An Initial Study... 

Figure 2. Thermal oxidative degradation of untreated Indiana Minshall Seam (HvCb) coal with and without a diluent...

Figure 4. Thermal oxidative degradation of untreated and oxydesulfurized Montana Rosebud Seam (Sub B) coal with diluent...

Table I. Coals Subjected to Thermal Oxidative Degradation of Sulfur...

Table n. Thermal Oxidative Degradation of Organic and Inorganic Systems... 

Figure 6. Comparison of a normal thermal oxidative degradation with an alternate programmed-isothermal treatment for oxydesulfurized Indiana Minshall Seam...

Figure 7. Comparison of the thermal oxidative degradation of oxydesulfurized Indiana Minshall Seam (HvCb) coal in oxygen and air...

---