STRUCTURE PROPERTY RELATIONSHIPS IN LCP/PEI BLENDS REVEALED WITH A NEW SELECTIVE ETCHING PROCESS

An etching technique for making visible the morphology of blends composed of polyetherimide and a liquid crystalline fully aromatic copolyester (LCP) has been developed. The four organic solvents - tetrachloroethane, N-methylpyrrolidone (NMP), dimethylformamide (DMF) and dimethylacetamide (DMAc) - selectively etch the polyetherimide without attacking the LCP component. By adjusting the etching conditions to the respective conditions prevailing within the samples, all the four solvents yielded equally good results across the entire concentration range investigated (from 20/80 to 80/20 percent by weight of LCP/PEI). The viscosity of the LCPs decreases markedly. with increasing shear rate. The large shear rate gradient from the mould edges to the centre results in different deformations of different volume elements within the melt. The resulting frozen-in morphologies can be visualized with the new etching technique. This allows one to explain certain correlations between morphology and mechanical properties of the respective samples.