The Effect of Polyamic Acid Binder Concentration on the Processability and Properties of LaRC TPI Composites Made by Suspension Prepregging

Unidirectional carbon fiber/LaRC TPI composites were prepared by aqueous suspension prepregging. The matrix material was fully imidized LaRC TPI powder, and the binder was LaRC TPI polyamic acid. The effect of the concentration of the polyamic acid binder on composite processability and properties was studied. An optimum concentration range of 2.9-9.4% weight/weight binder/matrix was found that resulted in good prepreg handling characteristics and good consolidation. A binder concentration 2 13.1% led to poorer consolidation of the composites due to an increase in the melt viscosity of the matrix. This increase was probably due to a combination of crosslinking and chain extension of the polyamic acid during the imidization step. Formation of the crosslinked structure was supported by transverse flexure, meso-indentation, and solubility tests.