Copolymerisation for Modified Properties
topic
Incorporation of co-monomers modifies PET crystallinity and dyeability: isophthalic acid (IPA) reduces crystallinity and improves dye uptake; 5-sodium sulphoisophthalate (SIIS) introduces anionic sites for cationic dye uptake (CDP polyester); PEG incorporation creates moisture-regain improvement; CHDM (cyclohexanedimethanol) produces amorphous coPET (PETG). Comonomers are added at 0.5–5 mol%.
Role
Copolymerisation is the primary molecular tool for tailoring polyester to specific end-use requirements — dyeability, softness, elastic recovery, or biodegradability — without major process changes.