PTT
Polytrimethylene Terephthalate
Glass Transition (Tg)
45–50 °C
Melting Point (Tm)
225–230 °C
Density
1.35 g/cm³
CAS Number
26925-16-6
Recycling Code
♺ 7
Category
Engineering
Repeat Unit
–[O–(CH₂)₃–O–CO–C₆H₄–CO]ₙ–
The repeating unit is the smallest structural fragment whose repetition builds the whole chain. Subscripts show the relative share of each unit in copolymers.
Key Properties
Odd number of methylene units creates a helical "kinked" chain giving exceptional elastic recovery; propanediol can be bio-derived.
Applications
Stretch carpet fibre, apparel, engineering resins.