In this research, rheological parameters of cement suspensions modified with different doses of two types of superplasticizers (SPs) were evaluated with an alternative method of centrifugation. It was determined that the critical normal and shear stresses (yield values), and the water/solid ratio alter with the additive dose, the additive type as well and the magnitude of centrifugal forces. The results obtained reveal that the method of centrifugation might serve for determination of dispersing effectiveness of SPs and rheological parameters of suspensions in general.

Abstract. The paper deals with the rheological behavior of highly filled compounds proceeded via powder injection molding (PIM) and applied in many sectors of industry (automotive, medicine, electronic or military). Online rheometer equipped with slit dies varying in surface roughness and dimensions was applied to investigate the wall-slip as a rheological phenomenon, which can be considered as a parameter indicating the separation of compound components (polymer binder and metallic powder) during high shear rates when injection molded.

Abstract. In this work, the low-flammability halogen-free polyolefin composites were characterized with three rheological methods. In the extrusion process of the studied materials the end-products with a dissimilar surface quality were produced. Therefore, the diverse melt flow behaviours evaluated with common rheological techniques were also expected. Nevertheless, the conventional rotational and capillary rheometries were not able to describe the differences between investigated flame retarded composites in optimal way. Thus, the non-conventional rheological die Shark skin, originally designed to detect flow instabilities, was tested as a third possibility in order to better understand rheology of the filled polymer melts. It was found that the Shark skin technique is able to characterize the studied two kind flame retardants composites and can also be helpful to qualify the production bathes with identical additives/polymer formulation.

Suspensions of two types of cements modified with different doses of melamine formaldehyde type of plasticizer were rheologically tested by an alternative method of centrifugation. The sorption of organic molecules on the cement particles was evaluated in order to verify the plasticizer efficiency. Regression analysis showed a considerable influence of the plasticizer's sorption on the rheological parameters of suspensions. POLYM. COMPOS., 34:1483–1488, 2013. © 2013 Society of Plastics Engineers

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