Preparation, Microstructure, And Property Of Silicone Rubber/Organically Modified Montmorillonite Nanocomposites

Silicone rubber (SiR) is a kind of elastomer with the largest use temperature range, and also one of the most widely used space sealing materials. But the gas barrier property of silicone rubber is the lowest among all elastomer materials. Clay sheet with high shape factor has been used to SiR to improve its gas barrier properties, but how to achieve the nano-dispersion is the key and difficult problems. This preparation methods and techniques of silicone rubber/organic modified montmorillonite (SiR/OMMT) nanocomposites were studied in this work; XRD and TEM characterization were used to characterize the intercalated structure of OMMT and the OMMT dispersion in the matrix; the relationship between the material structure and properties was revealed. The results showed as follows:1. Mechanical mixing method was used to blend liquid silicone rubber (LSR) and OMMT to prepare SiR/OMMT composites. The results showed that high temperature heat treatment play a good role to the clay intercalated; it is difficult to achieve nano-dispersion for OMMT in the LSR with low viscosity, so the LSR/OMMT composites performance poor properties. 2. Five different types of organically modified montmorillonites (OMMT) were incorporated into silicone rubber (SiR) respectively by melt blending. The results revealed that the organic intercalants or silane coupling agent having higher polarity might play the negative roles in the melt intercalation; and the higher the OMMT initial interlayer spacing, the easier the intercalation. The intercalated structure in the SiR/I.44P OMMT nanocomposite has the largest interlayer spacing and the best spatial dispersion of OMMT. The OMMT dispersion improves with increasing OMMT dosage. The gas barrier property of the SiR is obviously improved by the incorporation of OMMT. The nitrogen gas permeability coefficient of the SiR/OMMT nanocomposite is lower than that of pure SiR by 30% at an OMMT loading of 30 phr.3. In order to further improve the OMMT dispersion in SiR,20 phr fumed silica (FS) was added to the compound prior to mixing OMMT for increasing viscosity of the compound and mechanical shearing force during compounding OMMT. The results shown that though FS have no effects on the gas barrier properties of SiR/FS composites, the SiR/OMMT/FS ternary nanocomposites exhibit improved dispersion of OMMT and better gas barrier properties than the binary counterparts. The N2 gas permeability coefficient of SiR/OMMT/FS(100/30/20) nanocomposites decreases nearly 40% compared to net SiR.4. Hydroxyl silicone oil with different dosage (FS structural control agent) on the OMMT (I.44P) pre-intercalation to increase the initial lamellar spacing of OMMT, and then mechanically mixed with the premix of the MVQ Silicon 20 FS Preparation of rubber ternary nanocomposites, can OMMT dispersion in the SiR in further improvement. With the increased amount of silicone oil composites tightness and elongation at break increases the tensile strength decreased.5. Using mechanical blending method has excellent mechanical properties of commercial silicon rubber compound mixed with the preparation of OMMT nanocomposites. The results show that, due to the viscosity of the silicone rubber, OMMT dispersion in the SiR in better mechanical properties of composite materials with gas barrier properties are more desirable. When the clay content of 30 phr filled, OMMT nanocomposites was not added when the permeability of 50%.