PBI-polyarylate PA blends

Polyarylates are high temperature, high performance, thermoplastic polymers with good combinations of thermal and mechanical properties. 

They also have good processability, which allows them to be molded into a variety of useful articles. They are, however, limited in the aerospace industry, where the chemical resistance is limited in chlorinated solvents and inorganic acids. Blends have been reported with polyesters, as well as PEIs and polycarbonates and others. The property shortcomings of polyary lates can be substantially improved by incorporating PBI as a miscible blend. Beneficial properties are reported to be maintained and solvent, resistance, thermal, and physical properties can be improved at a moderate additional cost. 

FTIR and other analyses confirmed the existence of intermolecular hydrogen bonding between PBI and PA the carbonyl band shifts from 1741 to 1730 cm in an 80/20 blend. Also, miscibility and compatibility were indicated further by the clarity (visual and microscopic examination) of films prepared from the 80/20 blend TGAs showed blends conforming to the Rule of Mixtures, and X-ray diffraction (XRD) analysis confirmed that PBI and PA interact and are compatible on a molecular scale blends were found to have physical properties adhering to the Rule of Mixtures values the thermal stability of the blends at 550°C increased proportionately as the relative PBI concentration increased and after blending, the hydrophilicity of the PBI decreased dramatically. Thus, PAs and aromatic PBIs were found to be miscible in all proportions, and synergistic effects of one polymer over the other s weak properties can be achieved. 

PA is soluble in common organic solvents such as methylene chloride and tetrahydrofuran, whereas PBI is insoluble in these solvents. The two polymers can be simultaneously dissolved in a common solvent (DMF, DM Ac, DMSO, NMP, concentrated acid, such as sulfuric), or solution-derived miscible compositions of each polymer may be separately dissolved in separate volumes of a mutual solvent, and desired proportions of the resulting solutions can be mixed together to form a solution of the two polymers. If the blend is mostly PBI, the less expensive polyarylate should be added to an extent to take advantage of rendering the blend more tractable and processable, and less susceptible to moisture. If the blend is mostly polyarylate, then one should take advantage of PBFs 

---