Blends, alloys and interpenetrating networks

Polymer blends and alloys have more complex behavior in the presence of fillers than the binary mixtures of polymer and filler. The same factors, such as filler distribution, filler-matrix interaction, filler-matrix adhesion, particle orientation, nucleation, chemical reactivity, etc. have influence on properties, but this influence is complicated by the fact that there are two or more polymers present which compete for the same filler particles. These complex interactions result in many interesting phenomena discussed below. 

The above description stresses either chemical reactions in these combinations or physical interactions between components. In reality there is still additional effect which may induce changes to structure and thus properties. It is a commonly known effect of fillers on the nucleation of polymers. It can be perceived that filler does not affect nucleation of both polymers with the same intensity. In addition, the availability of polymers at the interface with fillers depends on various parameters such as viscosity, acid/base interaction, etc. If these two are included in the number of combinations, there is a theoretical abundance of possible combinations and thus 

This abundance of possibilities, combined with still large experimental difficulties in distinguishing between the numerous interactions and morphologies, creates opportunities more for the future than for todays benefit. The existing information is still on the very initial stage of understanding. Inverse gas chromatography was used to explain why, in polyamide-6/SAN blends. 

The phase morphology is modified by both fillers which help to micronize and homogenize both phases. Carbon black, in addition, acts as a compatibilizer, which is seen from shifts in the glass transition temperatures of both polymers and in a decrease in melting point of PVDF.  

It is not only the blend morphology which is affected by filler presence filler orientation might be affected by its surface treatment, as was observed in the works on PC/ABS blends containing aluminum borate whisker. When the whisker surface was treated with epoxy silane, its reaction to flow in injection and compression molding processes changed, resulting in a different orientation even though all other parameters of process and composition were the same.  

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