Intrinsic birefringence of amorphous poly(bisphenol-A carbonate)

✍ Scribed by Maan-Shii S. Wu

• Publisher: John Wiley and Sons
• Year: 1986
• Tongue: English
• Weight: 914 KB
• Volume: 32
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1986.070320129

✦ Synopsis

The birefringence of uniaxially oriented poly(bispheno1-A carbonate) (PC) samples stretched over a wide range of temperatures has been measured accurately with a combination of the compensator and the wedge methods. The Hermans' orientation function of anisotropic PC was calculated from the measured dichroic ratio of the infrared absorption band at 1364 cm -l . Measurements using differential scanning calorimetry, X-ray diffraction, or infrared spectroscopy indicated no stress-induced crystallinity in stretched amorphous PC. At each state having a defied molecular orientation, samples stretched below the glass transition temperature (T,) always exhibited excess birefringence and slightly higher density. This phenomenon is attributed to bond distortion during stretching, a result of the suppression of large-scale segmental motions of polymer chains below the T8. The birefringence of samples stretched above the T, arises exclusively from the orientation effect as a result of greater chain mobility.

These measured birefringence values are proportional to Hermans' orientation functions, yielding a linear relationship which allows precise determination of the intrinsic birefringence of amorphous PC as 0.192 f 0.006.