Addition of Fillers and Reinforcing Materials

Fillers are solid materials that are dispersed in plastics and elastomers. One distinguishes between inactive fillers that are used in the first place to make the plastics less expensive and active fillers (reinforcing fillers) that improve specific mechanical properties and thus effect a reinforcement . With the aid of these fillers, the elastic modulus, hardness, and thermostability are enhanced predominantly, whereas the impact strength of thermoplastic materials is reduced. Often the 

By the addition of glass fibers, textile fibers, or chopped fabrics to crossfinkable polymers molding materials are produced with increased tensile strength, stif tess, and thermal stability compared to the filler-free polymers. The so-called reinforcing fillers, like carbon black, have good adhesion to the matrix due to specific surface interactions and their characteristic geometry. 

During the last decade, nanofillers of different geometry, but in at least one dimension in the nanometer range, became more and more important. Examples are nanoclay (layered silicates, like montmorillonite), carbon nanotubes (single- and multiwalled), expanded graphite, and even graphene sheets. 

A speciality of such nanocomposites is the very high surface of well dispersed nanofillers, which results in a very high interfacial area. Here, the behavior of the polymer chains near the interface is influenced by the interaction with the filler, leading to an interphase with new properties which aheady at low amounts of nanofillers can determine the nanocomposite s properties. In addition, quite big effects are observed aheady at quite low filler loadings, especially if the filler has an anistropic shape. As an example, in thermoplastic polymers electrical conductivity can be reached with carbon nanotubes even below 1 wt% addition. 

In case of other fillers, the nanofillers can introduce new functionality into the polymer, e.g. electrical conductivity in case of carbon based nanoparticles, barrier properties in case of platelet like nanofillers (nanoclay, expanded graphite), enhancement of mechanical properties, enhanced flame retardancy, and many others. 

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