PHYSICAL STUDIES OF THERMOPLASTICS. I. MELTING TEMPERATURE MODIFICATIONS IN BISPHENOL A POLYCARBONATE. II. A MELTING POINT DEPRESSION STUDY OF POLYCARBONATE/POLYCAPROLACTONE BLENDS. III. THERMAL CONDUCTIVITY MEASUREMENTS OF ORIENTED POLYETHYLENES (DIFFUSIVITY, FLASH METHOD, MISCIBILITY, ANNEALING)

This dissertation discusses studies relating to the physical properties of thermoplastics. Separate investigations involving the melting temperature of a slow-to-crystallize polymer, thermal behavior of a miscible polymer blend, and thermal conductivity of oriented polyethylenes are presented. Polycarbonate is known to thermally crystallize slowly and to a limited extent, with a range of reported melting points. In this study, the melting temperature of polycarbonate was modified from 195(DEGREES)C to 300(DEGREES)C by employing a sequence of vapor-induced crystallization and annealing treatments. The crystals formed by the treatment with organic vapor act as a precursor state for further crystallization into larger, more perfect lamellae. An equilibrium melting point of 335(DEGREES)C has been obtained for PC from an extrapolation of reciprocal lamellar thickness. FTIR and SEC measurements confirm the Kolbe rearrangement reaction occurs only to a limited extent for the annealing procedure employed. The miscibility of bisphenol A polycarbonate (PC) / poly-(epsilon)-caprolactone (PCL) was investigated using DSC. A single glass transition was found across the compositional diagram, in accordance with an earlier study, yet no depression was observed in the melting points of either PC or PCL. For the PCL-rich blends, Hoffman-Weeks extrapolations are linear, and identical to the PCL homopolymer, thus the Flory ((chi)) interaction parameter must be zero or slightly positive for this blend. The PC Hoffman-Weeks extrapolation could not be made, since the blends are reactive at high crystallization temperatures. This reaction was demonstrated by FTIR, NMR, and turbimetric titration to be thermo-oxidative chain branching rather than transesterification between these two polyesters. Thermal conductivity measurements are not a routine experimental technique in the field of polymer science. In this dissertation, experimental methods for cylindrical and film sample geometries are explored. The flash technique for thermal diffusivity has been critically examined with regard to rear-face rise and front-to-rear temperature difference modes of analysis on a systematic series of drawn low-density polyethylenes. Correction procedures have been put forth for losses due to radiation and surrounding air. The increase in thermal conductivity was shown to be proportional to draw ratio. Work on a steady-state fin and a pulsed method for thin film measurements is also discussed