PBI-polyetherketoneketone PEKK blends

Blend patent work describes a process for producing a solution blend of PBI and an amorphous PEKK. The objective was to prepare solution-derived blends of 100-mesh PBI polymer with PEKK, and to evaluate the thermal properties (Figs 7.6 and 7.7 show the TGA curves for PBI and PEKK, respectively). The PBI is mixed with sulfuric acid at a temperature between 40°C and 80°C for 30 min to 2 h to produce a PBI solution, then cooled to 

78TGA curve of PBI/PEKK blends. Curves are displaced by 10 unit increment from bottom up. 

Unfilled grades of partially crystalline polymers such as PEEK are not very useful in molded part forms at temperatures much above their Tg since the softening that occurs leads to a sharp loss in polymer mechanical properties, especially stiffness/modulus. This lowered modulus is reflected in reduced dimensional stability under stress at temperatures above Tg. 

Polymer mixtures with PBI benefit from PBI s ability to immobilize the amorphous regions of the PARK matrix resin, thereby imparting enhanced thermo-mechanical properties not obtainable with other fillers of PARK, but which fall short of that obtained in a miscible blend of polymers. 

The Fox equation relationship (Rg. 7.10) defines or describes the composition dependence of the Tg of ideal co-polymer or ideal polymer blends (or miscible blends of two polymers) in which no strong interactions are involved. The Fox equation typically is expected to lead to a lower value of Tg than would be given by a simple linear Rule of Mixtures (Blend Inherent Viscosity vs. % Component in the Solution Blends) and reflects the effective higher free volume or randomness due to the presence of two components in the mixture  

---