Toughening mechanisms in polypropylene filled with rigid particles

Composites of polymer matrix and filler particles constitute an important class of materials. Filler particles are used to reduce overall cost and to improve the mechanical properties of the polymer matrix. Until recently, there exists a trade-off between stiffness and toughness in using filler particles in polymer composites. This thesis studies the mechanisms whereby both stiffness and toughness can be enhanced using rigid mineral filler particles. The mechanisms of deformation and fracture of isotactic polypropylene filled with CaCO3 particles were studied. In slow tension, addition of fillers increased the modulus and decreased the yield stress independent of filler type. An optimum size of particles was found to improve Izod impact energy up to four times that of the unfilled matrix. The toughening mechanisms at work were plastic deformation of interparticle ligaments following particle-matrix debonding with additional contribution coming from crack deflection toughening. The failure of too large or too small particles to toughen the matrix was attributed to poor dispersion. A study on the volume evolution of these composites during deformation revealed that measurement of volume strain can be used to identify the onset of debonding. It also provided a new evidence for the existence of an interphase layer between the filler particles and the polymer matrix. This layer is comprised of polypropylene chains strongly bound to the surface of the particles. The thickness of this layer was estimated to be 20 nm. The effect of particle-matrix interaction was investigated in a study of composites of isotactic polypropylene and glass spheres.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Thio, Yonathan Setioputra, 1977-

Advisor dc:contributor.advisor

• Robert E. Cohen and Ali S. Argon.

• Chemical 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/1721.1/29605

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/29605