Polymeric materials and process for producing same

An improved process for producing a consolidated polymeric monolith from an assembly of thermoplastic polymer. The assembly is placed under pressure to fill a majority of the voids thereof by mechanical deformation of the fibers, and heated to a temperature too low to melt the fibers at the deformation pressure but sufficiently high to at least partly melt the fibers at a lower transition pressure. While maintaining the assembly at this temperature, the pressure is reduced to the transition pressure long enough for partial melting of the fibers to fill the rest of the voids, and then is increased to a consolidation pressure at least as high as the deformation pressure. The assembly is cooled slowly to ambient temperature at the consolidation pressure. The process allows accurate control of thermal expansion coefficients of the product. Further, products of manufacture produced by the process exhibit improved strength, thermal stability, infrared transparency and unique intrinsic physical characteristics.