Effect of Processing Parameters on PP/EPDM/Organoclay Nanocomposites Using Taguchi Analysis Method

Thermoplastic elastomer nanocomposites based on polypropylene (PP) andethylene-propylene diene monomer (EPDM) and Cloisite 15A were prepared viadirect melt mixing in a co-rotating twin-screw extruder. The formulation forpreparation of nanocomposites was fixed with the ratio of 75/20/5 for PP/EPDM/organoclay©15A, expressed in mass fraction. The objective of the present study wasto investigate the effects of processing conditions on the formation of TPE(PP/EPDM/nanoclay) nanocomposites. The parameters under study included thefeeding rate, screw speed and barrel temperature, which were varied independently,from 0.2 to 1.0 kg/h and from 50 to 150 rpm and 180 to 200°C, in the order given.Design of experiments was carried out by Expert Design software (Taguchi AnalysisMethod) on the basis of three different levels of the above processing parameters. Thestate of dispersion was quantified by X-ray diffraction, transmission electronmicroscopy and rheological measurements. X-Ray diffraction results show that thenanocomposites obtained in different conditions have an intercalated structure and theproportion of exfoliation, estimated by rheological measurements, depend on theoperating conditions. The exfoliated layers increase when the feed rate and barreltemperature decrease and the screw speed increases. The study of linear viscoelasticproperties also shows that the storage modulus, G’, is very sensitive to the microstructureof the nanocomposite. A Carreau-Yasuda model with a yield stress isproposed to describe the rheological behaviour of these materials. The yield stress ofnanocomposites increases when the barrel temperature and feed rate are reduced andthe screw speed is increased.