Polymer filament. Polarised light micrograph of two extruded, liquid crystalline polymer filaments. The red and green colours highlight the regular contours on the filaments' surface. This is often seen on synthetic fibres. Extrusion is the process of forcing molten material through an aperture, to form a profile such as a fibre. Many polymers are ideal materials for extruding into fibres as they are not easily destroyed when melted. In the molten state they can be extremely easy to extrude and the fibres produced are strong and flexible. The fibres can be used for textile fabrics, tyre cords and fishing lines. Magnification: x25 at 35mm size.