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Supercritical fluid assisted process...

Yang, Kumin.

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Supercritical fluid assisted processing of nanoparticle/polymer composites.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Supercritical fluid assisted processing of nanoparticle/polymer composites./
作者:	Yang, Kumin.
面頁冊數:	154 p.
附註:	Adviser: Rahmi Ozisik.
Contained By:	Dissertation Abstracts International69-01B.
標題:	Chemistry, Polymer. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3299442
ISBN:	9780549439264

Supercritical fluid assisted processing of nanoparticle/polymer composites.
Yang, Kumin.

Supercritical fluid assisted processing of nanoparticle/polymer composites. - 154 p.

Adviser: Rahmi Ozisik.

Thesis (Ph.D.)--Rensselaer Polytechnic Institute, 2006.

An experimental study was carried out to determine the effects of supercritical fluids on the nanoparticle dispersion for various nanoparticle/polymer systems. The nanoparticles were classified according to forces that hold them together: (1) strong electrostatic interactions (montmorillonite); (2) physical entanglements (carbon fibers); (3) weak electrostatic interactions (untreated alumina); and (4) polar interactions (modified alumina). For the case of strong electrostatic attraction without supercritical fluid, pressure improved the clay delamination by reducing the free volume of the polymers and thereby augmenting the interaction between the chains, and ultimately increasing the viscosity and the wall shear stress. Using supercritical fluids such as carbon dioxide or 1,1,1,2-tetrafluoroethane did not ameliorate the clay dispersion for the 95/5 N6-L/20A because it resulted in an increase in the free volume and a decrease in the melt viscosity. For the carbon fibers/polystyrene system, the rapid expansion of the supercritical carbon dioxide (scCO2) did not improve the state of dispersion. This was due to the carbon fiber microstructure whose highly interwoven, physically entangled fibers resisted fiber pullouts or fracture. Spherical alumina, both untreated and modified, were also investigated in polystyrene using an autoclave at 17.7 MPa. All agglomerates were found inside the cells and the cell size increased with agglomerate size. For the untreated alumina, the sudden expansion of the carbon dioxide did not alter the size of the agglomerates. This was probably caused by the weak interaction of scCO2 with the untreated alumina and the relatively strong electrostatic interactions between the nanoparticles. In contrast to the three aforementioned cases, only the large agglomerates (L ≥ 15 mum) of the modified alumina showed signs of any catastrophic fragmentation. The fluorinated modifiers were found to be soluble in scCO 2 using solubility parameter analysis at the processing conditions and therefore, the scCO2 were able to diffuse easily into the modified alumina agglomerate compared to the untreated alumina. Large agglomerates can absorb more scCO2 than smaller ones; and therefore have an adequately larger bursting pressure to overcome both the hydrogen bonding between the modified alumina nanoparticles and the weak electrostatic interactions. Higher applied pressure may improve the dispersion of the modified agglomerates.

ISBN: 9780549439264Subjects--Topical Terms:

1018428
Chemistry, Polymer.

Supercritical fluid assisted processing of nanoparticle/polymer composites.
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502 $a Thesis (Ph.D.)--Rensselaer Polytechnic Institute, 2006.
520 $a An experimental study was carried out to determine the effects of supercritical fluids on the nanoparticle dispersion for various nanoparticle/polymer systems. The nanoparticles were classified according to forces that hold them together: (1) strong electrostatic interactions (montmorillonite); (2) physical entanglements (carbon fibers); (3) weak electrostatic interactions (untreated alumina); and (4) polar interactions (modified alumina). For the case of strong electrostatic attraction without supercritical fluid, pressure improved the clay delamination by reducing the free volume of the polymers and thereby augmenting the interaction between the chains, and ultimately increasing the viscosity and the wall shear stress. Using supercritical fluids such as carbon dioxide or 1,1,1,2-tetrafluoroethane did not ameliorate the clay dispersion for the 95/5 N6-L/20A because it resulted in an increase in the free volume and a decrease in the melt viscosity. For the carbon fibers/polystyrene system, the rapid expansion of the supercritical carbon dioxide (scCO2) did not improve the state of dispersion. This was due to the carbon fiber microstructure whose highly interwoven, physically entangled fibers resisted fiber pullouts or fracture. Spherical alumina, both untreated and modified, were also investigated in polystyrene using an autoclave at 17.7 MPa. All agglomerates were found inside the cells and the cell size increased with agglomerate size. For the untreated alumina, the sudden expansion of the carbon dioxide did not alter the size of the agglomerates. This was probably caused by the weak interaction of scCO2 with the untreated alumina and the relatively strong electrostatic interactions between the nanoparticles. In contrast to the three aforementioned cases, only the large agglomerates (L ≥ 15 mum) of the modified alumina showed signs of any catastrophic fragmentation. The fluorinated modifiers were found to be soluble in scCO 2 using solubility parameter analysis at the processing conditions and therefore, the scCO2 were able to diffuse easily into the modified alumina agglomerate compared to the untreated alumina. Large agglomerates can absorb more scCO2 than smaller ones; and therefore have an adequately larger bursting pressure to overcome both the hydrogen bonding between the modified alumina nanoparticles and the weak electrostatic interactions. Higher applied pressure may improve the dispersion of the modified agglomerates.
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