Compounding Particulate-Filled Polymer Composites

Machinery used to prepare particulate-filled polymer composites may be classified in terms of the applied shear intensity and whether the operation is of a batch or continuous nature. Furthermore, most compounding processes are critically dependent on the efficiency of ancillary equipment to undertake various functions, including additive and polymer feeding, melt filtration and pelletising procedures. 

Continuous forms of compounding plant engineered for the preparation of particulate-filled polymer composites are frequently based on variants of the extrusion machine, modified to impart increased mixing capability. 

Beyer G. Flame retardant properties of EVA-nanocomposites and improvements by combination of nanofiller with aluminium trihydrate. Fire Mater, 2001 25 pp. 193-197. Rothon NR. Particulate-Filled Polymer Composites. Harlow Longman Scientific 1995. Hawroth B, Raymond CL, Sutherland I. Polyethylene compounds containing mineral fillers modified by acid coatings. 2. Factors influencing mechanical properties. Polym Eng Sci, 2001 41 pp. 1345-1364. 

As was mentioned in the previous section two types of interactions must be considered in particulate filled polymers particle/particle and matrix/filler interaction. The first is often neglected even by compounders, in spite of the fact that its presence may cause composite properties to deteriorate significantly especially under the effect of dynamic loading conditions [18]. Many attempts have been made to change both interactions by the surface treatment of the filler, but the desired effect is often not achieved due to improper use of incorrect ideas. 

With this wide range of material types and approaches to compounding, incorporation of particulate additives into polymers can vary greatly from one compoimd to another. Attention will therefore be directed only on the main types of compoimding plant used industrially, highlighting their principles of design and operation specifically for the preparation of particulate-filled polymeric compositions. 

Whilst many of these areas fall outside the scope of this chapter, particulate polymer composites are becoming increasingly complex and commonly require more than just inclusion of a filler or particle additive in order to achieve optimum properties. For example, rubber modification of mineral-filled thermoplastics to yield a balance of enhanced toughness and stiffness, is an area of commercial importance. In these ternary-phase systems, there is not only a requirement to attain good dispersion of the filler component, but also a need for breakdown of the rubbery inclusion to yield the most effective size and spatial location within the composition. Whilst this may depend to a large extent on characteristics of the material s formulation, it can also be influenced by the material s compounding route. 

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