Masters Theses

Date of Award

12-2000

Degree Type

Thesis

Degree Name

Master of Science

Major

Polymer Engineering

Major Professor

Paul J. Phillips

Committee Members

R. S. Benson, K. M. Kit

Abstract

Aliphatic polycarbonates are a family of thermoplastics with a wide variety of properties and applications. The knowledge of structure- property relationships of these homologues is important to design the formulation that will produce the desired properties at the given operating conditions. The objective of the work is to characterize these polymers and correlate their properties with their structure. Specifically relationships between the thermal, mechanical, rheological and viscoelastic properties to the molecular structure of the polymers is discussed. Using the Differential Scanning Calorimeter (DSC) we found that the polymers are completely amorphous. We characterized the glass transition temperature and the thermal degradation properties of the polymers using the DSC. It was found that the glass transition temperature decreases with the decrease in the chain stiffness or increase in the length of the side groups present. The thermal degradation was also studied using the Thermo-Gravimetric Analysis. It was found that the polymers degrade completely with less than 10 % residue. The degradation temperature increases with the increase in the hydrocarbon content of the polymer chain. The tensile testing of the bulk samples showed that the mechanical properties are a strong function of the structure of the polymer. The polymers behave from highly rigid and brittle to rubbery at the room temperature depending on their structure. The effect of strain rate on the mechanical properties is also studied for one polymer. Dynamic Mechanical Analysis was used to study the relaxation phenomena in the polymers. The glass transition temperatures were found to be greater than those obtained from Differential Scanning Calorimetry. The activation energies and the entropies of the primary relaxation are correlated to the structure of the polymers. The Melt Flow Index studies were done on two polymers and the effect of the temperature was studied. The effect of the processing temperature on the surface roughness was studied for one polymer. The rheological properties were determined using parallel plate Rheometer. The effect of branching of the polymer and the molecular weight distribution on the rheological properties of the polymers is studied. These studies are important for the process design and product development using aliphatic polycarbonates

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