Particulate filled polypropylene: Structure and properties

The characteristics of all heterogeneous polymer systems including composites containing either micro or nano fillers are determined by four factors: component properties, composition, structure and interfacial interactions. The most important filler characteristics are particle size, size distribution, specific surface area and particle shape, while the main matrix property is stiffness. Segregation, aggregation and the orientation of anisotropic particles determine structure. Interfacial interactions lead to the formation of a stiff interphase considerably influencing properties. Interactions are changed by surface modification, which must be always system specific and selected according to its goal. Under the effect of external load inhomogeneous stress distribution develops around heterogeneities, which initiate local deformation processes determining the macroscopic properties of the composites. In filled polymers, the dominating deformation mechanism is usually debonding. Particulate filled polypropylene is used in many areas, but development never stops. Natural fiber and wood reinforced polymers, layered silicate nanocomposites and hybrid composites are in the focus of attention in recent times