Chemical Byproduct
Low molecular weight ring-shaped polymer molecules form as unintended reaction products during synthetic fibre synthesis. During high-temperature polyester dyeing, a cyclic oligomer migrates from the interior of the PET fibre matrix to the liquor and recrystallizes upon cooling. This crystalline deposit settles on package yarn surfaces, causing friction and thread breakage in subsequent weaving or knitting processes.
Deposition Mechanism
Thermal energy during high-temperature dyeing expands amorphous regions of polyethylene terephthalate, allowing trimeric and tetrameric rings to dissolve into the aqueous bath. As the bath temperature drops below eighty degrees Celsius, these solubilized ring structures precipitate out of solution and adhere to metal surfaces and yarn structures. Filtering mechanisms in machinery collect portion of the residue, but coarse microscopic crystals remain trapped on the filament exterior.
In spun yarns, deposits interfere with drafting and spinning stability, raising yarn tension and causing filament shear during high-speed rewinding.
Removal Protocol
Alkaline reduction clearing with sodium hydrosulfite and caustic soda hydrolyzes surface deposits into water-soluble monomeric units. Machine cleaning cycles utilize special oligomer dispersants alongside carrier solvents to scour internal pipework and package dyeing carriers.
Prevention Boundary
Specialty polyester polymers synthesized with controlled molecular weight distributions minimize initial ring formation during polymerization. Surface treatments reduce but cannot eliminate subterranean ring structures that migrate out during subsequent thermal processing runs.
