Poly(trimethylene terephthalate)

Abstract Poly(trimethylene terephthalate) (PTT) is a newly commercialized odd‐numbered aromatic polyester made by the melt polycondensation of 1,3‐propanediol and terephthalic acid. It has a melting point of 228°C and a glass‐transition temperature of 45°C. PTT crystallizes into triclinic unit cell with two chemical repeating units in the c ‐axis. The three methylene units are arranged in gauche–gauche conformation. Crystal and amorphous densities are 1432 and 1295 kg/m 3 , respectively. PTT crystallization rate is in between those of poly(ethylene terephthalate) and poly(butylene terephthalate), with a crystallization half‐time of 2.4 min at 180°C. A rapidly quenched PTT shows cold crystallization at about 65°C, which could affect its drawing behavior if crystallization were to occur during hot drawing. Heat of fusion of 100% crystalline PTT is 30 ± 2 kJ/mol. Isotropic PTT has a flexural modulus of 2.76 GPa and a tensile strength of 67.6 MPa. The notched Izod impact is 48 J/m. Current commercial applications are in textile and carpet fibers. Applications in monofilament, nonwoven, film, and engineering thermoplastics are under development. PTT is processed at 250–270°C. Melt viscosity of a 0.92 dl/g intrinsic viscosity fiber grade PTT is about 240 Pa·s at 265°C. PTT fibers are soft and have very good hand. It also has excellent elastic recovery similar to nylon fiber and is stain‐resistant. The fibers are disperse‐dyed at atmospheric boil without using a carrier.