Abstract

Compatibilization of incompatible isotactic polypropylene (iPP)/polyethylene oxide (PEO) is studied with an emphasis on the crystallization behavior of polyethylene oxide. An attempt is made to correlate the crystallization data for PEO obtained from optical microscopy, differential scanning calorimetry, x-ray diffraction, infrared spectroscopy and dynamic mechanical analysis. PEO and iPP are incompatible in the temperature range -50C to 200C. iPP was used as the matrix while PEO was used as the dispersed phase. Experimental observations demonstrated that PEO underwent fractionated crystallization in the blends in the temperature region from -10C to 40C when cooled at a rate of 10C/min. PEO domains nucleated homogeneously as well as heterogeneously in these blends. Larger domains (30-100 microns) crystallized at higher temperatures (heterogeneous nucleation), while smaller domains (10-60 microns) crystallized at lower temperatures (homogeneous nucleation). Heterogeneous nucleation occurred both thermally, and athermally. The graft copolymer, polypropylene-graft-maleic anhydride-graft-polyethylene glycol was used to increase compatibility between iPP and PEO. Three blends systems were studied; iPP and PEO, polypropylene-graft-maleic anhydride and PEO and polypropylene-graft-maleic anhydride-graft-polyethylene oxide and PEO. An increase in the concentration of PEO in the blends increased its crystallinity. However there was a decrease in the crystallinity of PEO, as the blends were made more compatible. This behavior of PEO was observed both by optical microscopy differential scanning calorimetry. Results from x-ray diffraction, however, showed an increase in the crystallinity of PEO relative to iPP as compatibility between the blends increased. The compatibilizer reduced the size of the dispersed phase thus increasing compatibility between iPP and PEO. There was clustering of small PEO domains in the compatibilized blends. Heterogeneous nucleation can be seen only for the 30% PEO concentration of the uncompatibilized blends. The melting point of PEO in the blends was depressed, while that of iPP was the same as the pure polymer. PEO domains existed as spherical droplets in the melt. The crystallization temperatures for PEO were higher when seen through optical microscopy as compared to differential scanning calorimetry. Results from infrared spectroscopy revealed a change in the nature of the spectra for iPP and PEO in the blends as compared to the pure spectra. The infrared spectra of the blends are distinctly different from the coadded spectra of iPP and PEO. Spectroscopy also revealed a change in the composition or structure of PEO in the blends from the targeted compositions. Mechanical analysis revealed a change in the nature of the graph of the loss modulus versus temperature, as the blends are made compatible. Crystal rearrangement of both iPP and PEO is seen as the blends were heated in the temperature range from -50C to 100C.

Library of Congress Subject Headings

Polyethylene oxide; Crystalline polymers; Crystal growth; Crystallization

Publication Date

8-1-2002

Document Type

Thesis

Department, Program, or Center

School of Chemistry and Materials Science (COS)

Advisor

Langner, Andreas

Comments

Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works. Physical copy available through RIT's The Wallace Library at: QD382.C78 I747 2002

Campus

RIT – Main Campus

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