Aging thermooxidative

LARC-TPI is a linear thermoplastic PI which can be processed ia the imide form to produce large-area, void-free adhesive bonds. Mitsui Toatsu Chemicals, Inc., has obtained Hcense to produce this product commercially for appHcations such as adhesives, films, mol ding compounds, etc. These are thermooxidatively stable and show essentially no loss ia weight at 300°C ia air. Weight loss does not exceed 2—3% after isothermal aging ia air at 300°C for 550 h. 

A PFMB-based polyimide (BPDA-PFMB) can be used to prepare fibers with mechanical properties comparable to those of commercial PPTA fibers. However, owing to superior thermooxidative stability, the fibers retain their properties for much longer periods of time when subjected to isothermal aging in air at elevated temperatures. In fact, BPDA-PFMB fibers retain their properties under these conditions better than any other available high-performance fiber. 

Thermooxidative and Photooxidative Aging of Polypropylene Separation of Heptane-Soluble and -Insoluble Fractions... 

INHAM-3 [131] contains up to 97 wt% PE and copper in the metal-polymer with the formula [—CH2—CH2—]nCum, dispersed rubber. Cl, unsaturated hydrocarbons of oil and PE copolymer with polyformaldehyde. This material shows high impact viscosity (see Table 4.13), resistance to thermooxidative aging (the strength does not impair upon thermal aging) and frost resistance (down to —70°C). 

Beside inhibiting thermooxidative ageing, phosphorus containing additives increase radiation resistance of polyimides and poly(alkyl terephthalates) the rate of evolution of the aromatic ring radiation degradation product - CH4 reduces two-fold. 

TPA amide is formed by thermo-oxidation in melt and at low-temperature solid-phase oxidation. Light yellow crystals of TPA amide and TPA mixture occur and accumulate on the surface of mould samples during accelerated heat ageing at temperatures of 150-200 °C. TPA is a typical product of hydrolysis by macrochain ends. From our point of view, TPA amide product is of greater interest. Recall that analogous products (relative to polymer structure) were already observed in investigation of thermo-oxidative transformations of other APH. For example, pyromellite diimide, was identified in thermooxidation of PAI [7, 21] and classical polyimide Capton , and 2,2 -(l,4-phenylene)-bis-(phenylpyrazine), is formed by poly(phenylquinoxaline) ageing [7]. 

Kozlov, G. V. Shustov, G. B. Zaikov, G. E. The structural aspect of the interrelation of the characteristics of thermal and thermooxidative degradation of heterochain polyethers. In book Aging of Polymers, Polymer Blends and Polymer Composites. V. 2. Ed. Zaikov, G. Buchachenko, A. Ivanov, V New York, Nova Science Ihiblishers, Inc. 2002,151-160. 

Thermooxidative Stability. Figures 3-6 detail the retention of PABM laminate (A-llOO finish) flexural strength and modulus after extended aging periods at temperature veurying from 355 to 480 F. 

TheCTial Aging. In addition to their high heat distortion temperatures and retention of properties at elevated temperatures, PABMs exhibit outstanding thermooxidative stabilities. 

Natural rubber-CaC03 nanocomposites Modified CaC03 addition into NR sulfur vulcanizing Calorimetry and thermogravimetric analysis for physical, thermooxidative aging and thermal degradation property assessment microstructure analysis [96]... 

First, the stability of these polymer materials is very important for their practical use and processing. Assessment of surface chemical modification of rubber after aging treatment is, by example, primordial for pneumatic manufacturing. Similar to conventional methods, LA-MS is allowed to evaluate and follow the oxidation effects on model polymers such as polybutadiene (PB), polystyrene (PS), and styrene butadiene rubber (SBR) by both detection and identification of the degradation products. The thermooxidative stability of SBR has been then investigated. 

For aging experiments which consist to realize the thermooxidation of polymer material, the operating temperature was 75°C in presence of air. Thin films prepared by spin coating were aged at this temperature. The exposure time was variable between 20 min and 600 h in order to obtain different oxidation degrees. 

Exposure of the molded HDPE articles to sunlight and air also attacks the polymer over time, especially at wavelengths less than 400 nm. Photooxidation resembles thermooxidation in that it is a complex chain of radical transformations. Such exterior aging of the polymer results in development of surface cracks, brittleness, changes in color, and a deterioration of mechanical and dielectrical properties. Photooxidation degradation is prevented by small amounts of light stabilizers, such as 2-4% carbon black or, for colorless articles, esters of salicylic acid or derivatives of benzotriazole or benzophone and others in the 0.1-0.5% range. 

The time evolution of the thermooxidative aging in SBR has been studied by NMR imaging (see Ref 145). In order to detect the aged surface layer with reduced... 

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