Alexandria Digital Research Library

Investigation of Thermal Stability and Flammability of Polyolefin Composites

Author:
Kunkel, Bryanna
Degree Grantor:
University of California, Santa Barbara.Chemistry
Degree Supervisor:
Scott Susannah
Place of Publication:
[Santa Barbara, Calif.]
Publisher:
University of California, Santa Barbara
Creation Date:
2011
Issued Date:
2011
Topics:
Chemistry
Keywords:
thermal stability
polyolefins
clay
flammability
nanocomposites
Description:

Organoclay-polyolefin nanocomposites are often reported to exhibit slightly increased thermal stability and decreased flammability, compared to unfilled polyolefins. In this thesis, we investigate the properties of nanocomposites containing clay that has not been organically-modified. They are less thermally stable but, unexpectedly, also much less flammable. We investigate the mechanistic origins of these surprising effects. Clay-polyolefin nanocomposites free of surfactants were prepared by in situ polymerization of ethylene or propylene, using a tetrabenzylzirconium catalyst adsorbed onto acid-treated montmorillonite. Their thermal decomposition was investigated qualitatively and quantitatively by anaerobic thermogravimetric analysis, pyrolysis-combustion flow calorimetry and volatiles analysis. The results are compared to those for the unfilled polymers, and for microcomposites prepared by melt-blending. Decreased thermal stability is attributed to clay-catalyzed polymer cracking, which has a lower activation barrierthan uncatalyzed thermal depolymerization. Decreased flammability arises in part because the acidic clay also catalyzes the formation of a polyaromatic char from olefins trapped in the solid material by the barrier effect of the dispersed nanofiller.

Composites containing either carbon black or fullerenes were prepared and their thermal stability was compared to unfilled polyethylene and clay-polyethylene nanocomposites. Fullerenes were found to be more effective than carbon black, achieving similar increases in aerobic thermal stability at much lower concentrations. Polymer composites were also produced in the presence of layered double hydroxides by in situ polymerization of ethylene in toluene and dimethylformamide. Unlike the acidic clay, layered double hydroxides do not exhibit a detrimental effect on the thermal stability of the polymer.

Format:
Text
Collection(s):
UCSB electronic theses and dissertations
ARK:
ark:/13030/m5rn38hx
Merritt ARK:
ark:/13030/m5rn38hx
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