Polymer-oxide adhesion: fabrication of a poly(dimethylsiloxane)/iron(III) oxide composite with a high compressive strength

Poly(dimethylsiloxane)/iron(III) oxide composite powders were obtained by t hermal treatment of polymer-oxide mixtures. The composites present themselv es as free-flowing powders, visually indistinguishable from the pure oxide. They are, however, highly hydrophobic and cannot be dispersed in polar sol vents. Cylindrical test specimens were obtained by pressing a composite pow der and heating it at two different temperatures. Specimens heated at 270 a nd 300 degrees C present compressive strengths of 1.19 x 10(7) and 1.55 x 1 0(6) N m(-2), respectively. Scanning electron microscopy of the fracture su rfaces reveals the presence of silicone-rich domains, these being larger an d more abundant in the specimens heated at 300 degrees C. These domains pro bably act as stress absorbent-dissipative sites which are responsible for t he high compressive strength of the composites.