Hybrid materials based composites continued

The hybrid materials having silica content below 50 wt% were composed of polyimide matrix with finely dispersed silica particles, and their hardness values were very close to that of the matrix polyimide. On the other hand, the hybrid materials having a silica content over 50 wt% were very hard and tough, and their hardness values increased with increasing silica content. In the latter hybrid materials, the silica formed a continuous phase with polyimide as the minor phase that probably acts as binder. This is a new type of polyimide-based composite, and may be referred to as polyimide-reinforced silica glass , al-... 

Although many kinds of fillers and fibers have been added to POs over the years, and new ones continue to be developed, the sections below cover the most used and most commercially important materials. These fillers and fibers continue to draw the greatest efforts from industry and academia for further development and improvement. Some newer kinds, such as nanofillers and plant-based fibers, are included here mainly because of their potential future importance. As in other chapters of this book, here the focus is more on materials that can be added in a typical compounding operation or "at the press"—rather than modifiers that are added more upstream by the resin producer, or hybrid combinations of materials, such as glass-mat composites or laminates, where the reinforcing material is not added during screw processing. 

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