BLENDING OF POLY(BENZIMIDAZOLE) (PBI) WITH A LOW-MOLECULAR-WEIGHT ETHER IMIDE MODEL-COMPOUND

Poly(benzimidazole) (PBI) was solution-blended with a low molecular ether-imide analog to Ultem 1000. The as-cast blends were found to form one-phase structures over the whole of the composition range. By the use of optical microscopy and differential scanning calorimetry, the blends were found to phase separate on heating above the blend glass transition temperature (T(g)) but did not remix on cooling. It was concluded that the blends formed on room temperature casting were nonequilibrium and remained one-phase simply because they were well below T(g).