A Study on the Size Effect Via Spectrophotometry and Impedence Measurements

Abstract

The optical and dielectric properties of polycarbonate films have been studied as a function of sample thickness. The observed optical energy gaps were determined from the absorption spectra. The dielectric constant was determined from impedance data collected in the frequency range of 30 Hz–40 kHz. Four polycarbonate thin sheets of different thickness (0.17, 0.25, 0.30, and 0.55 mm) were used to assess the size effect on the physical behavior of this material. It was found that the measured properties as optical energy gap, dielectric constant, refractive index, and glass transition temperature are nearly independent of the specimen thickness. In general, it can be seen that the processing conditions of the glassy polymer sheets are quite identical and not producing structural changes leading to detectable size effect.

Keywords:

• dielectric constant
• glass transition
• optical absorption
• polycarbonate
• refractive index
• size effect
• temperature
• thickness

The authors thank Dr. J. Starr of the General Electric Company in USA for providing the polycarbonate sheets. Dr. S. Saq'an carried out the UV-optical measurements during his work as a visiting scientist at the “Physics of Materials Laboratory” at the University of Jordan, in Amman, Jordan.