Characterization of two precursor polyblends: Polyhydroxyamide and poly(amic acid)

Blends of two precursor polymers, polyhydroxy amide (PHA) and poly(amic aci d) (PAA), were studied using differential scanning calorimetry (DSC) and th ermogravimetric analysis (TGA). The presence of PHA enhanced thermal and me chanical properties of the polyblends. All of the polyblended films showed large endothermic peaks that decreased monotonically with increasing heat t reatment temperature. The cyclization onset temperature (T-1), initial deco mposition temperature (T-2), and weight residue at 900 degrees C of the pol yblends were shown to be in the ranges of 144-146 degrees C, 532-540 degree s C, and 44-45%, respectively. Also, the thermal stabilities were enhanced consistently with increasing annealing temperature from 25 to 250 degrees C . The ultimate strength and initial modulus of the polyblends increased fro m 84 to 136 MPa and from 2.93 to 5.34 GPa, respectively, with increasing PH A content. Similar to the trend of thermal stability, increasing the anneal ing temperature of the polyblends increased the tensile properties of the f ilms. The observed tensile properties are discussed in terms of the morphol ogy of the fractured films as studied by scanning electron microscopy (SEM) . The degree of crystallinity of the polyblends was characterized as a func tion of heat treatment temperatures by wide angle X-ray diffractometry (WAX D).