Date of Award
Master of Science in Chemical Engineering - (M.S.)
Chemical Engineering and Chemistry
Richard G. Griskey
R. E. McMillan
Angelo J. Perna
The purpose of this investigation was to determine the dielectric constant and dissipation factor of atactic and isotactic polystyrene at 25°C and at frequencies of 0.1, 1.0, 10, and 100 kilocycles per second. In addition, the effects of molecular weight and crystallinity on the dielectric properties of polystyrene mos also studied.
Polystyrene slabs of uniform thickness mere prepared by molding the polymer under heat and pressure. The isotactic polystyrene slabs Imre annealed at 175°g for various lengths of time to achieve varying degrees of crystallinity.
The molded polystyrene slabs were fitted with circular aluminum foil electrodes to form a three terminal guarded electrode system. The electrical measurements were made using a variable capacitor in conjunction with a general Radio Impedance Comparitor. The capacitance and dissipation factor of the specimen was measured by using the variable capacitor as the standard to balance the impedance difference of the specimen.
It was found that the dielectric constant and dissipation factor of atactic polystyrene is independent of molecular weight within the range of 224,000 to 337,000. For very low molecular weight, 130,000, the dielectric constant increased.
The isotactic polystyrene was found to have a higher dielectric constant than the *tactic polystyrene. This increase was attributed to the stereoregularity of the isotactic polymer resulting in less dipole-dipole cancellation. Increasing the degree of crystallinity by annealing resulted in a decrease in dielectric constant indicating that the relaxation takes ply essentially in the amorphous phase. The dissipation factor of the isotactic polystyrene decreased with increasing frequency indicating the possibility of a maximum loss peak at a frequency lower than 0.1 kilocycles.
The dissipation factor and dielectric constant of stactic and isotactic polystyrene were found to be relatively low indicating a very low dipole moment per repeat unit or low polarity for polystyrene.
Kroplinski, Thaddeus F., "Dielectric properties of atactic and isotactic polystyrene" (1971). Theses. 2308.