Fabrication and characterization of silicone rubber/silane-modified nanodiamond nanocomposites
Topic(s) : Material science
Co-authors :
Noah UKAI (JAPAN), Seira MORIMUNE-MORIYA (JAPAN)Abstract :
Silicone rubber (SR) composites based on thermally conductive fillers are used in various electronic devices. In order to get more advanced features, the higher thermal conductivity is required to solve the high heat generation density in the electronic components. Therefore, conventionally, a large amount of thermally conductive fillers is introduced in SR composites. However, the enhancement in the thermal conductivity has been limited. In addition, poor interaction at the interface between SR and fillers has drastically reduced the flexibility of the material. Moreover, the increased weight has also limited the application of the products.
In this study, we prepared SR nanocomposites with nanodiamond (ND). ND is a nanocarbon material that has high modulus and high thermal conductivity derived from the diamond structure in the core. But ND is incompatible with SR because of various oxygen-containing functional groups on its surface. Therefore, in order to improve the compatibility with SR, we synthesized silane-modified ND (ND-Silane) by silane coupling treatment. The SR nanocomposites with non-modified ND or ND-Silane were prepared and the effect of silane coupling treatment of ND on the structure and properties of the nanocomposites were investigated.
Silane coupling treatment was conducted as follows. Firstly, ND was oxidized with air, and then mixed with the solution including silane coupling agent, water and ethanol. After heating and stirring, the resultant ND-Silane were washed and dried. The SR nanocomposites were prepared by in-situ curing. ND or ND-Silane suspension in acetone was added to the vinyl-polysiloxane solution and stirred. Subsequently, hydrogen-polysiloxane solution was added and further stirred. The mixture was casted and dried, followed by hot press. The SR/ND or SR/ND-Silane nanocomposites with the thickness of 0.2 mm were obtained.
According to the FT-IR spectra, it was revealed that carboxy groups were introduced on the surface of ND by the oxidation. In addition, the spectra indicates that silane was covalently bounded on the ND surface via ester bonds by silane coupling treatment. SEM images show a slight increase in the particle size of ND by the silane coupling treatment. It is due to the large molecular weight of silane molecules on the surface of ND-Silane. X-ray diffraction profiles suggests that the diamond structure in the core was maintained even after the modification.
Regarding the mechanical properties of the nanocomposites, the interesting results were obtained. The Young’s modulus of the nanocomposites increased by the addition of ND-Silane while it decreased by the addition of non-modified ND. ND-Silane can be incorporated in cross-linking network of SR due to the silane groups on the surface. On the other hand, it was assumed that the functional groups on the surface of non-modified ND prevented the cross linking in SR, resulted in the decrease in the mechanical properties.
In this study, we prepared SR nanocomposites with nanodiamond (ND). ND is a nanocarbon material that has high modulus and high thermal conductivity derived from the diamond structure in the core. But ND is incompatible with SR because of various oxygen-containing functional groups on its surface. Therefore, in order to improve the compatibility with SR, we synthesized silane-modified ND (ND-Silane) by silane coupling treatment. The SR nanocomposites with non-modified ND or ND-Silane were prepared and the effect of silane coupling treatment of ND on the structure and properties of the nanocomposites were investigated.
Silane coupling treatment was conducted as follows. Firstly, ND was oxidized with air, and then mixed with the solution including silane coupling agent, water and ethanol. After heating and stirring, the resultant ND-Silane were washed and dried. The SR nanocomposites were prepared by in-situ curing. ND or ND-Silane suspension in acetone was added to the vinyl-polysiloxane solution and stirred. Subsequently, hydrogen-polysiloxane solution was added and further stirred. The mixture was casted and dried, followed by hot press. The SR/ND or SR/ND-Silane nanocomposites with the thickness of 0.2 mm were obtained.
According to the FT-IR spectra, it was revealed that carboxy groups were introduced on the surface of ND by the oxidation. In addition, the spectra indicates that silane was covalently bounded on the ND surface via ester bonds by silane coupling treatment. SEM images show a slight increase in the particle size of ND by the silane coupling treatment. It is due to the large molecular weight of silane molecules on the surface of ND-Silane. X-ray diffraction profiles suggests that the diamond structure in the core was maintained even after the modification.
Regarding the mechanical properties of the nanocomposites, the interesting results were obtained. The Young’s modulus of the nanocomposites increased by the addition of ND-Silane while it decreased by the addition of non-modified ND. ND-Silane can be incorporated in cross-linking network of SR due to the silane groups on the surface. On the other hand, it was assumed that the functional groups on the surface of non-modified ND prevented the cross linking in SR, resulted in the decrease in the mechanical properties.