FLOW OF LIQUID-CRYSTALLINE POLYMERS THROU GH CYLINDRICAL CHANNELS ANDFIBROUS POROUS MATERIALS

A comparison investigation is undertaken of the flow of thermotropic l iquid-crystalline copolymer of n-hydroxybenzoic acid and poly(ethylene terephthalate), and of neat poly(ethylene terephthalate) through cyli ndrical channels and fibrous materials of various chemical composition s and morphological structures. It was found that, when flowing throug h channels, the copolymer behaves like a viscoplastic fluid with a pro nounced yield point, the yield strength decreasing with temperature. I t is shown that the flow of liquid-crystalline copolymer through fibro us materials can be quantitatively described as a flow of polymer thro ugh a porous medium with equal diameter capillaries. Of crucial import ance in this case are rheological of the polymer and such characterist ics of the fibrous medium as permeability and porosity. For fabrics, t hese parameters depend on both the fabric structure and the way the la yers of fabric are arranged in the sample. Using the available methods of theoretical analysis, we described quantitatively flow curves of t he liquid-crystalline polymer under investigation. Electron microscopy studies showed that the copolymer penetrates between complex fibers o f the fabric and between the filaments constituting these fibers. It w as also shown that the fibers of the copolymer are formed in such a ma nner that their long axes align along the reinforcing fibers.