Viscosity of siloxane gum and silicone rubbers

• Published in: Asia-Pacific journal of chemical engineering 2010-11, Vol.5 (6), p.882-894
• Main Authors: Crawford, B., Doherty, A. P., Spedding, P. L., Herron, W., Proctor, M.
• Format: Article
• Language: English
• Subjects: CFD; Computational fluid dynamics; die swell; Mathematical models; rheometry; Silicone rubber; siloxane gum; Siloxanes; Stresses; Viscometry; Viscosity; Wall slip
• ISSN: 1932-2135; 1932-2143; 1932-2143
• DOI: 10.1002/apj.419

Organo‐silicone compounds are widely used, have many desirable industrial properties and can exist in many different forms. Extrusion is the most commonly used manufacturing process of silicone products, and it is hoped that application of computational fluid dynamics (CFD) will elicit a better understanding of the underlying controlling mechanisms. In this work experimental data on viscoelastic properties obtained from rotational rheometry are presented for siloxane gums and silicone rubbers which, together with previous data on capillary viscometry and wall slip, will enable CFD simulations to be obtained which are more aligned to real behaviour. A general storage, loss moduli, viscosity curve was developed for the gum with an activation energy of 17.36 kJ mol−1. The equivalent could not be made from the room temperature rubber compound data. Wall slip occurred at all stress levels. A critical stress level necessary before slip took place may only be relevant for pressure‐driven flows. The Cox–Merz relation was of limited use. Die swell reduced with increased filler concentration but the extensional viscosity was found to increase. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.