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Addition of a Block Copolymer to Polymer Blends Produced by Cryogenic Mechanical Alloying

Summary: Addition of a Block Copolymer to Polymer Blends Produced by
Cryogenic Mechanical Alloying
Archie P. Smith,,# Harald Ade,*, Carl C. Koch, Steven D. Smith, and
Richard J. Spontak*,,
Departments of Materials Science & Engineering, Physics, and Chemical Engineering,
North Carolina State University, Raleigh, North Carolina 27695, and Corporate Research Division,
The Procter and Gamble Company, Cincinnati, Ohio 45239
Received September 10, 1999; Revised Manuscript Received November 29, 1999
ABSTRACT: Cryogenic mechanical alloying is used to incorporate a poly(methyl methacrylate-b-isoprene)
(MI) diblock copolymer into blends of poly(methyl methacrylate) (PMMA) and polyisoprene (PI). Mechanical
milling of the copolymer promotes a reduction in the molar mass of the M block, as discerned from glass
transition temperature measurements performed by thermal calorimetry, and induces chemical cross-
linking of the I block, as determined from sol-gel analysis. These effects become more pronounced with
increasing milling time. Morphological characterization of PMMA-rich PI/MI/PMMA blends by X-ray and
electron microscopies reveals that the characteristic size scale of the minority phase decreases with
increasing MI content, as well as milling time. The nanostructural features observed in such blends are
retained at relatively high MI concentrations during subsequent melt-pressing. Impact testing demon-
strates that the blends become tougher upon addition of the MI copolymer, even at relatively low copolymer
concentrations. Blend toughness likewise increases with increasing milling time up to a point, beyond
which phase inversion occurs within the ternary blends (the PI becomes continuous) and impact strength


Source: Ade, Harald W.- Department of Physics, North Carolina State University


Collections: Physics