Compounding machinery

The relatively low capital investment associated with compounding machinery (usually less than 1 million for a line, compared with many millions for a conventional reactor), coupled with a processing need for small amounts of tailored materials, allows small and mid-sized compounding companies to take advantage of producing reactive polymers. 

This section will consider the fundamental aspects of melt-mixing fillers and polymers, the apphcation of these principles to the design of polymer compounding machinery and the practical application of this and ancillary technology. 

It is the intention to consider the design features of polymer compounding machinery in terms of their functional capabilities, as identified previously, specifically in relation to the processing of filled polymer compositions. 

Salden, D. M., Melt Compounding and Compounding Machinery, 1st Major Conf. on Thermoplastic Compounding, PRl, London (1978). 

Introduction to Polymer Compounding Machinery and Technology, Volume 2... 

In essence these products have been introduced to make FRs easier to use. They allow faster production rates in compounding machinery due to their pre-dispersed nature. 

Cary, P., The Asbestos Panic Attack, U.S. News World Report, February 20,1995. Changing Market in Compounding Machinery, PE Europe, May 2003. 

The report does not cover polymerisation additives, compounding machinery or masterbatches ( concentrates ). Nor does it cover some of the more specialised additives used in active packaging, such as oxygen scavengers, or those that are specific to the thermosetting resin, rubber and coatings industries. 

The fillers most commonly treated are silicas, clays and other silicates and flame retardants such as aluminium and magnesium hydroxides. While both in situ and pre-coating methods are utilised, pre-coating is most popular. This is in part at least due to the problems that can be encountered due to alcohol release in compounding machinery when the in situ process is used. 

Surface treatment of fillers is common to minimise particle interaction and to facilitate dispersion. Additionally, appropriate treatment will lower the filler surface energy, thereby increasing compatibility with the polymer phase. This will aid wet-out hy the melt and may result in enhanced physical properties depending on the relative interaction between surface modifier, filler and polymer. It will be evident from the previous discussion that dispersion will be determined by the level of shear stress experienced hy the filler particles, which in turn is dependent on process-operating conditions and above all, hy compounding machinery design (Figure 5.1). 

Residence time distribution measurements not only generate information about the processing history of a polymer, but have also been used to characterise the conveying and self-cleaning efficiency of compounding machinery. 

Studies of the processing behaviour of thermoplastic elastomers carried out by Berstorff are reported, and developments by the Company in processing methods and machinety for these materials are examined. These include extmsion compounding machinery, extmders for the production of solid profiles and for the coextrusion of profiles combining solid and foamed thermoplastic elastomers with mbbers, and a process for the extmsion of foamed profiles using water as blowing agent. 

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