Ganesh Latta

Publication Date

5-2008

Advisor(s) - Committee Chair

Wei-Ping Pan

Comments

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Degree Program

Department of Chemistry

Degree Type

Master of Science

Abstract

The nanocomposites of ethylene octene copolymer (Engage®) with an organically modified (dimethyldioctadecyl quarternary ammonium chloride) montmorillonite (M-MMT) clay were synthesized by using a solution intercalation technique. The intercalation of M-MMT layers for M-MMT loading of 2.5-7.5% was verified by the shift of X-ray diffraction peak to a lower angle, showing a change in basal d-spacing from 1.26 for M-MMT to 1.35 nm. Internal structure and dispersion state of M-MMT in the nanocomposites were observed by transmission electron microscope, which confirmed the clay in the intercalated state. Thermomechanical analysis results showed improved dimensional stability under compression at 30°C for nanocomposites with increasing M-MMT loading. By DMA, the storage moduli of nanocomposites below glass transition temperature were higher than the neat Engage and increased with increasing M-MMT content. The glass transition temperature, however, was lowest for the nanocomposite containing 2.5% M-MMT (E-2.5M-MMT), suggesting the optimal concentration of M-MMT in nanocomposite being 2.5% or higher from the viewpoint of thermal properties. The oxidation induction time (OIT) of the nanocomposites was obtained by using pressure-differential scanning calorimeter. The Engage/M-MMT nanocomposites were superior in thermal oxidation resistance as compared to the neat Engage, with E-5.0MMMT yielding the highest OITtime value.

In further studies, the Engage was modified by radical initiated grafting of maleic anhydride (MA). The grafting of maleic anhydride onto Engage chain was confirmed by the presence of a carbonyl peak in FTIR analysis and the higher atomic percentage of oxygen by X-ray photoelectron spectrometer (XPS). The MA grafted Engage (MA-g-Engage) was used for the synthesis of MA-g-Engage/M-MMT nanocomposites. The intercalation of M-MMT is verified by both XRD results and TEM. TEM images showed the mixed system for 5% clay loaded sample was intercalated as well as exfoliated. Below glass transition temperature, the storage modulus of MA-g-Engage is higher than the neat Engage. The shift of the glass transition temperature to higher value for the MA-g-Engage sample confirms the grafting and increased interaction between the chains. The glass transition temperature decreases with increasing clay loading to 5% and then increases for 7.5%. The thermal stability of MA-g-Engage/M-MMT nanocomposite was higher than the Engage/M-MMT nanocomposite. The increased thermal stability for MA-g-Engage/M-MMT nanocomposite is attributed to the good dispersion of clay, increase in the polymer filler interaction and a higher extent of intercalation and exfoliation of clay.

Disciplines

Chemistry | Physical Sciences and Mathematics

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