Fibrillation in the flow of polyoxymethylene melts

The phenomenon of specific fibrillation from melts of polymer mixtures is considered (using mixtures of polyoxymethylene with copolyamide as an example) when, in contrast to conventional fibre spinning methods, a complex thread consisting of hundreds of thousands of ultrafine fibrils oriented along the extrusion axis is obtained as a result of compressing the melt mixture through a single orifice (or upon extension of one stream of the polymer melt mixture). Here we deal with a radically new process of fibrillation of one of the polymers of the mixture (under the effect of the rheological forces at the capillary inlet) in the matrix of the other, when the number of the filaments in the thread is not determined by the number of the orifices in the die.After solvent extraction (from the solidified extrudate) of the polymer forming the matrix the other component remains as a bundle of fine fibrils less than 1 μm in diameter. The microstructure of mixture extrudates depends on the rheological properties of the melt, the mixture composition, the conditions of mixing and extrusion. Capillary viscometry methods have revealed a drastic difference in the viscoelastic properties of melt mixtures as compared with the separate components.