Solution Cross-Linked Natural Rubber (NR)/Clay Aerogel Composites

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• 作者：Tassawuth Pojanavaraphan ; Lei Liu ; Deniz Ceylan ; Oguz Okay ; Rathanawan Magaraphan ; David A. Schiraldi
• 刊名：Macromolecules
• 出版年：2011
• 出版时间：February 22, 2011
• 年：2011
• 卷：44
• 期：4
• 页码：923-931
• 全文大小：930K
• 年卷期：v.44,no.4(February 22, 2011)
• ISSN：1520-5835

文摘

Aerogels are structural materials with ultralow bulk densities (often less than 0.1 g cm^鈭?), which stand out as good candidates for a variety of applications. In the present study, natural rubber (NR)/clay aerogel composites were produced by freeze-drying of the aqueous aerogel precursor suspensions, followed by solution cross-linking of the aerogel samples in benzene using sulfur monochloride (S₂Cl₂) as a cross-linking agent. The influences of cross-linking conditions, i.e., cross-linker concentration and reaction temperature, as well as polymer loading on the aerogel structure and properties were investigated. 1% (v/v) of S₂Cl₂ and reaction temperature of 鈭?8 掳C were found to be the optimum conditions for producing a strong and tough rubber composite; the 2.5 wt % NR aerogel, for example, after being cross-linked, exhibited a compressive modulus of 1.8 MPa, 26 times higher than that of the neat control. These favorable mechanical properties are attributed to the high local concentration of rubber and S₂Cl₂ in the freeze-dried structures, giving rise to the high cross-linking efficiency. Increasing the rubber concentration led to a substantial increase in the mechanical strength, in accord with the changes in microstructure and degree of cross-linking. The swelling capacity of the NR aerogels decreased with either increasing the cross-linker concentration or decreasing the weight fraction of rubber. Cross-linking of the rubber aerogels brought about increased thermal stability, consistent with restricted thermal motion of NR chains.