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P. Jakubowska, T. Sterzyński, B. Samujło

Rheological studies of highly-filled polyolefinic composites taking into consideration p-v-T characteristics

Polimery 2010, No 5, 379


DOI: dx.doi.org/10.14314/polimery.2010.379

Summary

A general characteristic of fillers, the various modification possibilities and the consequences of their modification on the properties of composites prepared with their participation was initially presented. The results of rheological studies of highly-filled (48-64 wt. %) polyolefin composites, in which calcium carbonate in the form of i-PP/CaCO3 was used as filler for PE-HD, have been presented (Table 1). Common analysis instruments - rotational cone/plate rheometer, extrusion plastometer of varying piston load and a twin-barrel capillary rheometer were used for rheological measurements. The viscosity curves (off-line method) of the composites were compared to those obtained directly during extrusion (in-line) in an extrusion rheometer, equipped with an rheological head with removable nozzles (Figs. 3-9). The studies were carried out on three types of composites comprising mixtures of PE-HD with i-PP, commercial concentrates and concentrates produced under laboratory conditions, depicted as R, H and M groups, respectively. The shear thinning phenomenon which can be described as an observed decrease in the viscosity of the composites caused by an increase in the shear rate and also in the filler content. The latter was observed especially in the low shear rate region and barely noticeable under high shear rate conditions. A comparison of the viscosity curves obtained for the studied materials in the off-line and in-line methods reveals a similar dependence in both cases. This clearly emphasizes the importance of taking into consideration the changes in density as well as the slippage effect caused basically by the modifying filler (in this case stearic acid and waxes) occurring during analysis. This slippage directly influences the rheological properties of components with a high filling degree of modified calcium carbonate.


Key words: polyolefins, calcium carbonate, composites, filler modification, rheological properties, slippage phenomenon


e-mail: Paulina.Jakubowska@put.poznan.pl


P. Jakubowska, T. Sterzyński, B. Samujło

Rheological studies of highly-filled polyolefinic composites taking into consideration p-v-T characteristics