Highsilicone Austempered Ductile Iron

Ductile iron casts with a higher silicone content were produced. The austempering process of high silicone ductile iron involving different austempering times was studied and the results presented. The results of metallographical observations and tensile strength tests were offered. The obtained results point to the fact that the silicone content which is considered as acceptable in the literature may in fact be exceeded. The issue is viewed as requiring further research

High Temperature Ceramifying Behavior of SR/Al2O3 Composites

In this work, silicone/alumina composites with 33 wt.% silicone content are prepared by compression mould technique. TGA, XRD and SEM were used to characterize the ceramifying behavior when the samples were heated from 600 to 1600°C. XRD results suggest that the ceramic residue of SR could restrain the phase transformation of γ-Al2O3 below 1100°C, indicating that the chemical bonds preserve the mechanism strength of SR/Al2O3 composites under high temperature. The flexural strength increases from 18.19 MPa to 75.31 MPa with the increasing temperature from 600 to 1600°C, owing to the sintering reaction between SiO2 and Al2O3 forming mullite phase under higher temperature. It has low liner shrinkage after firing and nearly no macrocracks or deformation under any temperature, illustrating that the SR/Al2O3 composites can be used as organic fire-retardancy materials.

Structures and Gas Separation Properties of Silicone-Containing Polyimides

In order to obtain polymer materials suitable for thermally stable gas separation membranes, silicone-containing polyimides (SPIs) with various chemical structures and silicone contents were prepared, and the relationship between the chemical structures and the gas separation properties was studied. The permeability of gases such as oxygen, nitrogen, carbon dioxide and methane increased with the silicone content, while the permselectivity decreased. Therefore the permeability and the permselectivity were found to be controlled by the silicone content as well as the chemical structure of the SPIs.

The preparation of poly(methylsilsesquioxane) network-polyimide hybrid materials by the sol-gel process and their properties

Poly(methylsilsesquixoane) network (silicone)-polyimide hybrid materials were successfully prepared by the sol-gel reaction of methyltriethoxysilane (MTES). The ethoxysilyl group in MTES was hydrolyzed and polycondensed in the solution of the polyamic acid, derived from pyromellitic dianhydride and bis(4-aminophenyl)ether, in N,N-dimethyl-acetamide (DMAc). The hybrid films were obtained by casting the reaction mixture, followed by heating up to 300°C. The hybrid materials containing 0-60wt% of silicone afforded flexible films. The films containing less than 7 wt% silicone were yellow and transparent, whereas the films with higher silicone content were yellow and opaque. Silicone particles with a diameter of around 1-10 μm were observed in the fracture surface of the hybrid films by scanning electron microscopy. Although the tensile strength and tensile modulus of the films obtained decreased with increasing silicone content. the value of the elongation at break remained at 60% up to 30% silicone content.

The preparation of new poly(phenylsilsesquioxane)-polyimide hybrid films by the sol-gel process and their properties

The preparation of poly(phenylsilsesquioxane)-polyimide hybrid films was successfully performed with phenyltriethoxysilane (PhTES) and the polyamic acid (polyimide precursor) prepared from 4.4'-oxydianiline (ODA) and pyromellitic dianhydride (PMDA). During the heating process at 300 C, the imidization of the polyamic acid and the sol-gel reaction, hydrolysis and condensation of PhTES, proceeded simultaneously. The IR spectrum and the t3C-NMR and 29Si-NmR spectra showed that the sol-gel reaction of PhTES proceeded in the polymer matrix with high conversion. The hybrid films with a silsesquioxane content up to 75 wt% were obtained as the self-standing form. The hybrid films having a silsesquioxane content of 45 wt% were yellow and transparent, and those having more silicone content were yellow and translucent. The therma] properties of the hybrid films were improved to some extent by the introduction of the silsesquioxane component into the polyimide matrix. With respect to the tensile properties. the tensile strength remained around 85 MPa up to a silicone content of 45 wt%. This value was twice that of the hybrid films based on methyltriethoxysilane. The tensile modulus decreased with increasing silsesquioxane content.