Thermooxidative, generally

To improve the processability of PPQ, appropriate phenylquinox-aline oligomers were end-capped with acetylenic groups using 3-(3,4-diaminophenoxy)phenylacetylene (43) or 4-(3- and 4-ethynyl-phenoxy)benzil (44, 45) (Eq. 10). The processability was improved but at the sacrifice of the thermooxidative stability. In general, cured acetylene-terminated heterocyclic polymers are less stable in a thermooxidative environment than the parent linear polymer. 

Because of its extended polyconjugated framework, polymer (210) exhibits semiconducting properties both by itself and in the presence of additives. Perhaps a more remarkable property, however, is that polymer (210) does not burn when exposed to a flame. Thus, by employing this thermooxidative reaction, woven or knitted poly(acrylonitrile) fibers can be transformed into fire-proof materials. Polymer (210) can be pyrolyzed still further at temperatures generally in excess of 1000 °C to expel all heteroatoms and generate carbonized or graphitized fibers. These fibers find application where an inert, extremely high temperature, e.g. up to 3000 °C, material is required. 

From Figure 2.37 it is seen that introduction of dyes increases thermal stability of PVA in the air, moreover it depends not only on the character of the found dye-polymer, but on chemical structure of the dye itself. So, the highest effect appears in phthalocyanine dyes, then follow azodyes and antrachinone dyes have the least effect. At the same time general tendency to improve stability to thermooxidative destruction for samples, containing covalently linked dyes, is displayed here. 

The definition of a general nature thermooxidative the collapse of the copolymers carried out by the method of differential thermal analysis (DTA) and thermo gravimetric analysis (TGA). 

Oxygen atoms in a hydrocarbon chain give torsional mobility and materials flexibility. Nearby skeletal units have to be taken into consideration as ether linkages are generally stable to hydrolysis and to thermooxidation while polyaldehydes depolymerise readily at moderate temperatures. 

The chemical structure of the polyamide does not influence the general direction of thermooxidation. Great influence is exerted by the degree of orientation. Thus, for example, in weakly oriented capron film, structuring processes occur at an appreciable rate at only 160°C, while a nonswelling polymer with a dense network is formed at 170°C [29]. 

Starch can be nsed as a natural filler in traditional plastics (11,23-33) and par-ticnlarly in polyolefins. When blended with starch beads, polyethylene films (34) biodeteriorate on exposure to a soil environment. The microbial consumption of the starch component, in fact, leads to increased porosity, void formation, and the loss of integrity of the plastic matrix. Generally (32,35-38), starch is added at fairly low concentrations (6-15%) the overall disintegration of these materials is achieved by the use of transition-metal compounds, soluble in the thermoplastic matrix, as pro-oxidant additives which catalyze the photo- and thermooxidative process (39-44). 

Key properties of aromatic polyimides are their outstanding thermooxidative stability and high resistance to radiation and to deformation under load at elevated temperatures. This section discusses the properties of polyimides in general. 

Generally speaking, polymers containing e.g., ether and sulfone linkages exhibit lowered thermooxidative stability but increased solubility and flexibility, which facilitates the further processing, modification (cross-linking and... 

Generally [17], starch is added at fairly low concentrations (6-15%) the overall disintegration of these materials is achieved by the use of transition metal compounds, soluble in the thermoplastic matrix, as prooxidant additives which catalyse the photo-and thermooxidative process [18-21]. 

Fig. 3.30). Mass loss may be categorized as volatile components such as absorbed moisture, residual solvents, or low-molecular-mass additives or oligomers that generally evaporate between ambient and 300 °C reaction products, such as water and formaldehyde from the cure of phenolic and amino resins, which generally form between 100 °C and 250 °C and generation of volatile degradation products resulting from chain scission that generally require temperatures above 200 °C but not more than 800 °C. All of these mass loss processes may be characterized by TGA to yield information such as composition, extent of cure, and thermal stability. The kinetics of these processes may also be determined to model and predict cure, thermal stability, and aging due to thermal and thermooxidative processes.

The same general features of temperature dependence have been substantiated on a variety of polymers by yet other investigators [67, 73]. Akutin and co-workers [67], studying injection molding, found that polycarbonates broke down more extensively by thermooxidation than in com-... 

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