Improving the Exfoliation of Layered Silicate in a Poly(ethylene terephthalate) Matrix Using Supercritical Carbon Dioxide

Type of Document Master's Thesis
Author Samaniuk, Joseph Reese
Author's Email Address jsamaniu@vt.edu
URN etd-05042008-010025
Title Improving the Exfoliation of Layered Silicate in a Poly(ethylene terephthalate) Matrix Using Supercritical Carbon Dioxide
Degree Master of Science
Department Chemical Engineering
Advisory Committee
Advisor Name Title
Donald G. Baird Committee Chair
John Y. Walz Committee Member
Richey M. Davis Committee Member
Keywords

* PLSN
* polymer-layered silicate nanocomposite
* poly(ethylene terephthalate)
* supercritical carbon dioxide
* nanoclay

Date of Defense 2008-04-29
Availability unrestricted
Abstract

Supercritical carbon dioxide (scCO2) was used as a processing aid to improve the level of exfoliation achievable in a PET-layered silicate nanocomposite produced from melt compounding. Layered silicate and scCO2 were allowed to mix for a period of time before being released into the second stage of a single screw extruder. The rapid expansion forced silicate particles into a modified hopper containing neat PET pellets. The mixture of layered silicate and PET was immediately melt mixed in a single screw extruder, cooled in a water bath and pelletized. Two sets of samples each containing layered silicate with different surface chemistries were produced with this method at 1, 3 and 5 wt% silicate. For comparison, samples of the same weight fraction and type of silicate were produced from a traditional melt compounding method. Wide angle x-ray diffraction (WAXD), mechanical testing and rheological analysis were used in order to characterize the silicate morphology, the composite mechanical properties and the relative amount of degradation between the various samples. Results show that scCO2 processed samples contain a higher degree of layered silicate exfoliation than samples produced with traditional melt compounding. Mechanical property improvements are shown to be dependent on the type of silicate surface modification employed. Finally, degradation of the PET matrix appears to be far less extensive in the scCO2 processed samples as shown from rheological data.

free literature