Topic
Rheometer
About: Rheometer is a research topic. Over the lifetime, 5759 publications have been published within this topic receiving 125849 citations.
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TL;DR: In this article, the influence of boron nitride on the rheology and processability of polyolefins was studied using an Instron capillary rheometer equipped with capillary and special annular dies.
Abstract: The influence of a new processing additive (fine particles of boron nitride) on the rheology and processability of polyolefins is studied. The equipment used includes an Instron capillary rheometer equipped with capillary and special annular dies (Nokia Maillefer wire coating crosshead) and two rheometers, namely a parallel-plate and a sliding-plate rheometer. Several types of boron nitride powders, varying in average particle size and distribution and in morphology are tested at various concentration levels. The additive with the smallest average particle size and free of agglomeration was found to have the greatest influence on the processability (melt fracture performance) of the polyolefins tested. Specifically, it was found that boron nitride not only eliminates surface melt fracture but also postpones the critical shear rate for the onset of gross melt fracture to significantly higher values, depending on the additive concentration, surface energy, and morphology. A flow visualization technique was used to visualize the polymer flow at the entrance of a transparent capillary die in order to determine the mechanism by which boron nitride eliminates gross melt fracture.
56 citations
TL;DR: In this article, the authors proposed a control scheme to maintain a constant strain rate of the mid-filament diameter in a filament stretching rheometer for polymer melts, cast as a velocity algorithm and consisting of a feed-back and a feed forward contribution.
Abstract: We propose a new control scheme to maintain a constant strain rate of the mid-filament diameter in a filament stretching rheometer for polymer melts. The scheme is cast as a velocity algorithm and consists of a feed-back and a feed-forward contribution. The performance of the controller is demonstrated on a commercial low-density polyethylene. Several strain rates and experimental conditions are tested to demonstrate the necessity of the control parameters and the limits of both the control scheme and the experimental apparatus. When the control parameters are properly tuned, the algorithm ensures that the applied strain stays within 2% of the set point and measurements can be made up to Hencky strains of 6.5.
56 citations
TL;DR: In this article, a split-bottom ring shear cell is used for powder flow simulation, where the bottom plate is split such that the outer part of it can move with the outer wall, while the other part (inner disk) is immobile.
56 citations
TL;DR: In this article, a rheological study was carried out on EOC/PP and EPDM/PP blends, and the oscillatory flow properties of pure polymers and blends were determined at 220°C on a cone-plate rheometer at an angular frequency ranging from 0.01 to 100 rad/s.
56 citations
01 Jan 1999
TL;DR: In this article, a new type of rheometer was developed to measure these two parameters and experimental works were conducted on the imitative concrete as well as the real one, in which the rheological properties of the matrix and the volume fraction of aggregates were variously changed.
Abstract: Self-compacting concrete (SCC) can produce much higher fluidity with no occurrence of segregation, thanks to its lower yield value and higher viscosity than conventional concrete. However, the fresh property of SCC cannot be evaluated by conventional consistency test such as slump test. It must be evaluated from the rheological point of view, of which SCC is considered as a Bingham plastic fluid with two parameters, the yield value and plastic viscosity. A new type of rheometer was developed to measure these two parameters and experimental works were conducted on the imitative concrete as well as the real one, in which the rheological properties of the matrix and the volume fraction of aggregates were variously changed. The result of this research allow us to develop an important parameter in establishing a new mix design method for the SCC.
56 citations