Thermomechanics of nano-filled elastomers

The incorporation of nanoparticles into engineering thermoplastic elastomers affords engineers an opportunity to formulate flexible, tough and multifunctional polymer nanocomposites that potentially rival the most advanced materials in nature. Development of these materials is difficult since thermodynamic and kinetic barriers inhibit the dispersal of inorganic, hydrophilic nanoparticles into inherently hydrophobic polymer matrices. Thermoplastic polyurethanes (TPUs) are particularly attractive nanocomposite matrix materials due to their vast range of potential applications (e.g. in artificial organs, coatings, foams, and active wear), their mechanical versatility, and tunable block-polymeric structure. In this thesis we explore methods for systematically nanoreinforcing such materials by exploiting the microphase structure, differential polarities and multiple thermomechanical phase transitions of the macromolecular blocks that constitute the elastomeric matrix. Using a solvent exchange technique we show that it is possible to preferentially nanoreinforce the hard micro-domains of thermoplastic elastomers with smectic clay nanofillers that have characteristic dimensions similar to the hard segment. The adhesion between the clay and the hard micro-domains coupled with the formation of a percolative network not only stiffens and toughens, but increases the heat distortion temperature (HDT) of the material. The discotic clay platelets induce morphological ordering over a range of length scales that results in significant thermomechanical enhancement and expands high temperature applications. This thesis seeks to further enhance the understanding and utility of thermoplastic polyurethane nanocomposites by answering two questions: (1) what thermo-physical interactions between nano-clay and elastomeric thermoplastic polyurethane are taking place? and (2) how can these thermo-physical interactions be exploited?

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Liff, Shawna M. (Shawna Marie)

Advisor dc:contributor.advisor

• Gareth H. McKinley.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/46494

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/46494