PTT (Polytrimethylene Terephthalate) Fibre
topic
PTT (polytrimethylene terephthalate): polyester with 1,3-propanediol (PDO) instead of EG. Helical chain conformation in crystal (unlike planar PET) provides spring-like elastic recovery: >95% at 20% extension (vs. PET 85%). Lower modulus (~20 cN/dtex) → softer fabric. Tg 45°C, Tm 228°C. Dyed with disperse dyes at 100–110°C (lower temperature than PET due to lower Tg). Commercial: DuPont Sorona® (bio-PDO from corn, 37% bio-content). Used in stretch fabrics, carpet, and athletic wear.
Role
PTT represents a structurally distinct member of the polyester family where chain geometry (helical vs. planar) produces fundamentally different mechanical behaviour. It exemplifies the principle that polymer architecture determines fibre mechanical character.