Heat-resistant adhesives heterocyclic polymers

During 1960—1970, an impressive number of heterocycles were engaged in macromolecules without taking into account their processability. At the present time, a few heterocyclic polymers have found general acceptance in the industry as heat-resistant adhesives, dielectric and insulating films, high-modulus fibers, protecting overcoats, and matrices for composites. The... 

Many trends in polymer synthesis generally are being applied, or could be applied in the future, to adhesives. There is a continuous stride toward polymers with superior heat resistance. To achieve this, various heterocyclic and aromatic structures are built into polymers, e.g., by intramolecular cyclization (polyimides, polybenzimidazoles), trimerization of terminal acetylene or nitrile groups, etc. Another route is to introduce highly stable perfluorinated units into the polymer. While heat-resistant polymers find their main applications as laminating... 

An impressive amount of data published in the literature indicates, based on TGA, that many heterocyclic polymers can be used at temperatures more than 350—4(X) °C. All experiments conducted later with these polymers, in actual long-term thermal operations, showed that heat-resistant polymers exhibit only a very short-term thermal stability at the onset of degradation revealed by TGA. In actual use, the thermal stability of a given polymer is approximately 150 to 2(X) °C less than the value provided by dynamic TGA. However, it is worth noting that significant differences exist between materials such as films and adhesives. In the former case, the surface area subjected to pyrolysis or oxidation is far greater than the periphery of an adhesive joint. 

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