ADHESIVE EVALUATION FOR NEW FORMS OF LARC(TM)-TPI

LARC(TM)-TPI is a linear aromatic polyimide that was developed at NASA Langley Research Center in the 1970's and subsequently licensed to Mi tsui Toatsu Chemicals, Inc., (MTC) in Japan. This company has made it easier to process for use in application as a structural adhesive or a s a composite matrix resin. The present forms that exist are (1) high melt viscosity or Low Flow Grade (LFG); (2) medium melt viscosity or M edium Flow Grade (MFG); and (3) low melt viscosity or High Flow Grade (HFG). As expected, the low melt viscosity material is the easiest to process but has poor toughness; the high melt viscosity material is ve ry tough but is more difficult to process. Because of these two extrem e situations we have worked closely with MTC to develop an optimized s ystem. This work has resulted in the medium melt viscosity material as well as two other modified or blended medium-flow variations. These n ovel forms of LARC(TM)-TPI have resulted in adhesives that can be melt processed at pressures as low as 0.01 MPa (15 psi) at temperatures be tween 343-371 degrees C (650-700 degrees F). Evaluation of adhesive pe rformance has been accomplished using lap shear specimens and evaluati ng flow, wet out and shear strength. Initial strengths for these optim ized materials range from 20.7-41.4 MPa (3000-6000 psi) at room temper ature and 13.8-20.7 MPa (2000-3000 psi) at elevated test temperatures.