Phase Transition
Thermal processes occurring during the high-temperature finishing of synthetic textiles determine the cleanliness of manufacturing equipment. The occurrence of oligomer evaporation during the heat-setting of polyester fabrics results in the release of low-molecular-weight polymer fragments into the air stream of the tenter frame. This phase transition occurs at temperatures above the polymer melting point.
Equipment Impact
Condensation of these airborne polymer particles on the cooler surfaces of the exhaust ducts creates a sticky residue. When oligomer evaporation is heavy, the build-up can drip back onto the moving fabric web, causing permanent oil-like spots that ruin the finished roll. Frequent cleaning of the exhaust system is necessary to prevent these defects.
Control Strategy
Dyehouses address this issue by pre-treating polyester fabrics with specific scour chemicals that remove surface oligomers before heat-setting. If oligomer evaporation is not controlled, the accumulated deposits can also clog the air circulation nozzles, leading to uneven drying and temperature variations across the fabric width. Installing modern exhaust filtration systems with electrostatic precipitators helps capture these vaporised compounds before they condense on machine surfaces.
This equipment modification reduces maintenance downtime and improves air quality.
Fabric Assessment
Mill inspectors check the surface of processed polyester rolls under high-intensity lights to locate spots caused by polymer condensation. If oligomer evaporation has occurred, these spots will appear as shiny, non-absorbent patches on the fabric. Correct drying temperatures and pre-treatment steps prevent these quality failures in production.
