ORIENTATION OF RESEARCH ON HIGH-PERFORMAN CE ADHESIVES

The high performance adhesives must exhibit good mechanical properties in a wide range of temperatures in different environments for a long time. The aromatic and heterocyclic structures are needed to obtain ch emical and thermal resistance. The linear polymers offer good mechanic al properties in term of fracture toughness, but they require high tem perature and high pressure for the processing in order to insure good wettability. In addition, the temperature service is limited by the tr ansition. Some examples of linear polyimide will be discussed. The cro sslinkable systems are telechelic aromatic oligomers with end groups s uch as maleimides, acetylenes or nadimides. These systems offer good w ettability, but the cure cycle is more complicated than the one of lin ear system. The mechanical properties are maintained up to 370 degrees C for a short period of time. The blend of linear polymer and crossli nkable oligomers were studied in this case of epoxy resins and elastom ers and thermoplastics. Recently, it was mentioned that the blend of l inear polyimides and crosslinkable bismaleimide or bis-nadimide improv e the properties of each component, and these semi-IPN'S concept will be presented.