Influence of incorporating CaCO₃ into room temperature vulcanized silicone sealant on its mechanical and dynamic rheological properties

Abstract

Abstract Silicone sealants with low modulus and high elongation were prepared by using ketoxime silane as chain extender agent, and a novel silane coupling agent acting as adhesion promoting agent was synthesized. Mechanical properties of vulcanized polydimethylsiloxane (PDMS) filled with large amounts of carbonate calcium (CaCO 3 ) and dynamic viscoelastic properties of unvulcanized samples were investigated through electronic multifunctional tensile tests, dynamic mechanical analyzers, and dynamic rheological measurements. The results of mechanical tests indicate that diminishing the particle diameter size, narrowing the particle diameter distribution, and increasing the filler amount lead to a relative high tensile strength and modulus at 100% elongation, but a relative low elongation at break. The reasons for these are believed to be the evolution of molecular interactions and the formation of additional physical crosslinking induced by the filler network. Compared to virgin PDMS, there is a significant elevation of glass transition temperature with filler addition. On the other hand, the results of dynamic rheological measurements reveal that as filler amount increases, the span of the linear viscoelastic region in which dynamic storage modulus (G′) is constant in low strain amplitude narrows. However, a characteristic plateau phenomenon appears in low frequency regions together with increasing the width and height of the modulus plateau. This phenomenon is also ascribed to the formation of a filler network due to filler–polymer and filler–filler interaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2027–2035, 2007