Thermally stimulated current studies on molecular relaxation and blow moulding of poly(ethylene terephthalate)

✍ Scribed by Satoto, Rahmat; Morikawa, Junko; Hashimoto, Toshimasa

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 104 KB
• Volume: 48
• Category: Article
• ISSN: 0959-8103
• DOI: 10.1002/(sici)1097-0126(199906)48:6<509::aid-pi183>3.0.co;2-w

✦ Synopsis

The thermally stimulated current (TSC) technique has been used to investigate molecular relaxation in poly(ethylene terephthalate) (PET) ®lms unstretched and biaxially stretched at 90 and 95 °C. Unstretched PET ®lms show two peaks at 77 and 90 °C corresponding to a and r relaxation processes, respectively. The a relaxation is associated with the main glass transition of the material. The r peak with lower intensity is attributable to permanent dipoles. Both biaxially stretched samples show one TSC peak at 95 °C, supposed to correspond to r relaxation. The disappearance of the a peak, accompanied by the displacement of the r peak to higher temperature, is the result of the higher thermal stability of the permanent dipoles, which is strongly in¯uenced by the stiffening of amorphous parts and the crystallization by stretching. In both stretched samples, the continuous distribution of pre-exponential factors over activation energies observed might correspond to a single relaxation mode. The kinematics of stretching PET has been discussed in terms of activation energy and temperature dependence of relaxation time.