Polymer thermal oxidative degradation

Polymers may be attacked by molecular oxygen, ozone, or by indigenous free radicals in the polymer. Thermal-oxidative degradation of polyolefins in air is autocatalytic, i.e., the rate is slow at first but gradually accelerates to a constant value. According to the three-step mechanism outlined below, the RO2 peroxy radicals formed (Step 1) are sufficiently reactive to attack some primary CH bonds of the chain R H (Step 2). The peroxy radical RO2 is thus reformed (Step 3) and can attack another CH bond. This chain reaction continues until termination occurs (Step 4) [1-11]. 

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... 

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. 

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... 

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

To clarify the mechanisms of the clay-reinforced carbonaceous char formation, which may be responsible for the reduced mass loss rates, and hence the lower flammability of the polymer matrices, a number of thermo-physical characteristics of the PE/MMT nanocomposites have been measured in comparison with those of the pristine PE (which, by itself is not a char former) in both inert and oxidizing atmospheres. The evolution of the thermal and thermal-oxidative degradation processes in these systems was followed dynamically with the aid of TGA and FTIR methods. Proper attention was paid also to the effect of oxygen on the thermal-oxidative stability of PE nanocomposites in their solid state, in both the absence as well as in the presence of an antioxidant. Several sets of experimentally acquired TGA data have provided a basis for accomplishing thorough model-based kinetic analyses of thermal and thermal-oxidative degradation of both pristine PE and PE/MMT nanocomposites prepared in this work. 

A pioneering and comprehensive study of the effect of copper on the thermal oxidative degradation of polyolefins has been made by a Bell Laboratories research group (1-6). They found that surface reactions at the interface between metal and polymer are important factors in many applications including metal-polymer composites, polyolefin-insulated... 

Simultaneous cross-link formation and chain scission, which occur during the thermal-oxidative degradation of many elastomers, transform the polymer into a harder but weaker material having a consistency that can best be described as cheesy. 

Butyl Polymers. The outgassing products from the butyl polymers also initially condense out as liquids and are slowly converted into tan colored solid varnish-like deposits. These resinous deposits are formed through a thermal oxidative degradation process as follows ... 

EPDM Polymers. The condensable materials from the EPDM polymers, though different in composition, still formed resinous, varnish-like products through a thermal oxidative degradation process. The liquid condensates did not adversely affect light transmittance. The solid products produced a significant reduction similar to the solid product obtained from the butyl polymers and the processing oils. 

Reduction of the thermal and thermal-oxidative degradation of the polymer matrix,... 

Nakatani H., Suzuki S., Tanaka T. and al. "New kinetic aspects on the mechanism of thermal oxidative degradation of polypropylenes with various tacticities". (2005). Polymer. V.46. No ll.PP.12366-12371. 

Compositions were prepared by blending CN with melted polymer in a laboratory mixer Brabender at 190°C. TOPANOL (l,l,3-tris(2-methyl-4-hydroxy-5-t-butylphe-nyl)butane) and dilamylthiodipropionate (DLTP) were added in the amount of 0.3 wt% and 0.5 wt% as antioxidants to prevent thermal-oxidative degradation during polymer processing. 

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