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

Thermoplastic elastomer nanocomposites based on polypropylene (PP) and ethylene-propylene diene monomer (EPDM) and Cloisite 15A were prepared via direct melt mixing in a co-rotating twin-screw extruder. The formulation for preparation 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 was to investigate the effects of processing conditions on the formation of TPE (PP/EPDM/nanoclay) nanocomposites. The parameters under study included the feeding 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 Analysis Method) on the basis of three different levels of the above processing parameters. The state of dispersion was quantified by X-ray diffraction, transmission electron microscopy and rheological measurements. X-Ray diffraction results show that the nanocomposites obtained in different conditions have an intercalated structure and the proportion of exfoliation, estimated by rheological measurements, depend on the operating conditions. The exfoliated layers increase when the feed rate and barrel temperature decrease and the screw speed increases. The study of linear viscoelastic properties also shows that the storage modulus, G’, is very sensitive to the microstructure of the nanocomposite. A Carreau-Yasuda model with a yield stress is proposed to describe the rheological behaviour of these materials. The yield stress of nanocomposites increases when the barrel temperature and feed rate are reduced and the screw speed is increased.