Masters Theses

Date of Award

8-1992

Degree Type

Thesis

Degree Name

Master of Science

Major

Polymer Engineering

Major Professor

Joseph E. Spruiell

Committee Members

Dondald C. Bogue, Jack F. Fellers

Abstract

A study was carried out to determine processing parameters and to characterize oriented films prepared from copolymers of styrene maleic anhydride (S/MA) with 8 % and 14 % maleic anhydride. The purpose of this study was to investigate the potential of these films for packaging applications that would withstand the temperatures of foods being heated in microwave ovens. Studies on the pure homopolymer of polystyrene were also done in order to provide comparison of the S/MA material to that of a similar material of known properties. Oriented films from uniaxial to biaxial nature were prepared for each grade under a range of process conditions using a biaxial stretching apparatus. The resulting films exhibited a range of molecular orientations and mechanical properties.

In general the molecular orientation increased with increase in the stretch ratio and strain rate. Films prepared from compression molded plaques had more uniform and reproducible properties than the same films produced from plaques cut from extruded sheets. Thus residual orientation in the sheet prior to stretching plays an important role in successfully orienting and predicting the properties of S/MA films prepared from extruded sheets.

The optimum process temperatures for S/MA 3000FG (14 % MA) was 170°C while S/MA 2000 FG (8 % MA) and PS (0% MA) processed at the lower temperatures of 155°C and 140°C , respectively. The differences in processing temperatures reflects the variation of the Tg of the polymer with increase in the maleic anhydride content.

The degree of molecular orientation for all the grades investigated was found to be very sensitive to the stretch temperature. Increase in the stretch temperature sharply decreased the final orientation in the films.

For the optimum process temperature range, for a common stretch ratio and strain rate, the tensile strengths of these polymers in decreasing order were S/MA 3000FG > S/MA 2000FG > PS.

Films of polystyrene prepared under identical conditions but three different starting thicknesses of 14 mils, 21 mils and 26 mils gave maximum strengths and molecular orientation in films prepared from plaques of 21 mils starting thickness.

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