Rheological properties of carbon mixes at very low shear rates using a capillary rheometer—III

✍ Scribed by G. Bhatia

• Publisher: Elsevier Science
• Year: 1976
• Tongue: English
• Weight: 266 KB
• Volume: 14
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(76)90002-6

✦ Synopsis

capillary rheometer has been used to determine the rheological properties of carbon mixes consisting of petroleum coke as filler and coal tar pitch as binder. It is shown that carbon mixes behave as Bingham materials with definite yield stresses. The yield stress was found to be a general property of all carbon mixes and its value is independent of the size of the capillary die. It was also seen that extrusion at low shear rates through big diameter capillaries results in slipflow. The slipflow occurs when the applied stress is somewhat below the yield stress, the material then extrudes without the formation of a core which otherwise would cause cracks in the product after baking. This explains why big diameter rods are generally extruded at very low speeds in usua1 manufacturing process. The modified Buckingham-Reiner equation has been applied to the case of slipflow and the values of yield stress and plastic viscosity calculated. These values agree well with those obtained from the consistency curve.