Thermal Separation
A purification technique spreads a liquid mixture into a thin layer on a heated surface to evaporate volatile components quickly. In polymer and synthetic fibre production, thin film evaporation is used to remove residual monomers and solvents from polymer melts. This process prevents the thermal degradation of the polymer by reducing its exposure to high temperatures.
The purified polymer melt is then ready for high-speed spinning.
Mechanical Action
Rotating blades or wipers continuously distribute the polymer melt across the inner wall of a cylindrical heated chamber. This thin film evaporation creates a high surface-area-to-volume ratio, which accelerates the release of volatile residues. The vacuum applied to the chamber lowers the boiling point of the volatile compounds, allowing them to evaporate at lower temperatures.
This mechanism is ideal for heat-sensitive textile polymers, protecting them from thermal breakdown.
Quality Impact
Removing volatile impurities prevents the formation of gas bubbles in the polymer melt during extrusion. These bubbles can cause filament breakages in the spinneret, leading to yarn defects or line shutdowns. Consistent use of this purification step improves the tensile strength and uniformity of the drawn polyester or nylon yarn.
This treatment is a standard step in high-grade filament production.
Process Limitations
The high viscosity of some polymer melts can restrict the flow through the evaporator, requiring higher rotor speeds. This mechanical limitation must be managed to avoid polymer shearing.
