Fiber Spinning, Structure, and Properties of Poly(ethylene terephthalate-co-4,4‘-bibenzoate) Copolyesters

• Published in: Macromolecules Vol. 35; no. 13; pp. 5123 - 5130
• Main Authors: Ma, Hongming, Hibbs, Michael, Collard, David M, Kumar, Satish, Schiraldi, David A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 18-06-2002
• Subjects: Applied sciences; Exact sciences and technology; Fibers and threads; Forms of application and semi-finished materials; Polymer industry, paints, wood; Technology of polymers; Stretchability; Molten state; Property composition relationship; Mechanical properties; Melt spinning; Experimental study; Property processing relationship; Molecular relaxation; Random copolymer; Ester copolymer; Hot drawing; Oriented copolymer; Activation energy; Ethylene terephthalate copolymer; Rheological properties; Crystalline structure
• DOI: 10.1021/ma012245h
• EISSN: 1520-5835
• ISSN: 0024-9297

Thermal, rheological, and fiber spinning behavior of poly(ethylene terephthalate-co-4,4‘-bibenzoate) random copolymers containing 5−65 mol % bibenzoate (BB) units have been studied. Copolymer randomness was determined by 13C solution NMR. Copolymers with >40 mol % BB units spin like thermotropic liquid crystals and have mechanical properties approaching those of liquid crystals; however, no evidence of liquid crystallinity was observed in these fibers based on thermal, optical, and rheological studies. Thus, we believe these polymers are frustrated liquid crystalline polymers. The α-relaxation attributed to the glass transition temperature is completely suppressed in the fully drawn and heat-treated PETBB55 fibers. Structure development during fiber spinning as well as fiber mechanical properties have been studied. Fibers containing more than 40 mol % bibenzoate show the development of a new crystal structure and exhibit much higher tensile modulus than the copolymers containing a lower bibenzoate percentage. Copolymers containing more than 40 mol % bibenzoate also exhibit high melt relaxation times compared to the lower bibenzoate copolymers.