AFM and UFM surface characterization of rubber-toughened poly(methyl methacrylate) samples

The microstructure of a series of injection-molded and extruded rubber-toug hened poly(methyl methacrylate) (RTPMMA) samples was investigated. Atomic f orce microscopy (AFM) and ultrasonic force microscopy (UFM) were used to st udy surface topography and local elastic properties. AFM topography measure ments combined with UFM can reveal the distribution and orientation of the rubber particles in the PMMA matrix. UFM, in particular, reveals the core-s hell structure of the particles as well as the presence of particles immedi ately under the surface, otherwise invisible, In some cases the particles a ppear to be covered by a thin PMMA layer, whereas in other cases they appea r to have broken, thereby exposing parts of their internal structure. Gener ally, the particles are elongated in the skin region of the injection-molde d samples. On the other hand, the particles in the surface region of the ex truded samples appear to be almost spherical. The observed difference is at tributed to the fountain flow phenomenon, which takes place during injectio n molding. (C) 2001 John Wiley & Sons, Inc.