Synthesis and characterization of modified phenylethynyl imides

As an ongoing effort to develop structural adhesives for high-performance aerospace applications, recent work has focused on phenylethynyl terminated imide (PETI) oligomers. The work reported herein involves the synthesis and characterization of a series of phenylethynyl containing oligomers designated LARC(TM) MPEI (modified phenylethynyl imide). These oligomers presumably contain mixtures of linear, branched and star-shaped molecules. The fully imidized polymers exhibited minimum melt viscosities as low as 600 poise at 335 degrees C, significantly lower than equivalent molecular weight linear materials. Ti/Ti lap shear specimens processed at 288 degrees C under 15 psi showed tensile shear strengths as high as similar to 6000 psi and similar to 5200 psi at ambient temperature and 177 degrees C respectively. The chemistry and properties of these new MPEIs are presented and compared with an optimized linear PMI, LARC(TM) PETI-5.