Matrix-Fibril Morphology and Structure of Polyblend Fibers in Melt Spinning Process: A Review

The mechanism and the parameters affecting the matrix-fibril morphology in melt spun polyblend fibers are discussed. The properties of polymeric blends depend considerably on their final morphologies. Blending of two miscible polymers, normally gives rise to formation of a single-phase morphology while blending of two immiscible polymers can create a two or three (in case of using compatibilizer) phase morphology. Disperse phase in matrix phase could be formed in different shapes with playing important parts in the final properties of the blends. Though, formation of multiphase morphology may result in deterioration of physical properties, by choosing proper components and polymer blend contents, these properties can be improved. In immiscible polymeric blends depending on polymer processing methods various morphologies can take shape. However, in melt spinning process due to intensive extensional flow at take-up region the most convenient conditions for creation of matrix-fibril morphology can be achieved. According to various reports, extensional fields are acting more effectively than shear fields to shape the matrix-fibril morphology. In addition, extensional flows can reduce fibrils' diameter while enhancing fibrils lengths evenness. However, reducing the ratio of disperse phase to matrix phase viscosity (ηd/ηm) increases the probability of fibrils formation, in such a way, that even in the fields with zero extension force still fibrils formation phenomenon can occur. The finest fibrils' diameter in viscosities ratio of around 1 (ηd/ηm=1) was observed. Using compatibilizing agents also can reduce fibrils' diameter.
On the effect of viscoelasticity parameter of two-component system some researchers have reported that; when matrix phase elasticity is higher than the disperse phase, the morphology of the fibrils still remain unchanged. Changing the blend ratio of the two-phase polymers may also have effect in the formation of the number of fibrils and their diameters.