Preparation and Performance of Poly(silicon-alkyne imide) Resins and Their Composites

Silicon-containing arylacetylene resin has excellent heat resistance and low-temperature curing properties. Its main defects are the brittleness of the cured resin and poor interface adhesion with the reinforcement. Polyimide (PI) resin has good thermal and mechanical properties, and excellent interfacial adhesion with reinforcement. The idea of copolymerizing PI and silicon-containing arylacetylene resin is proposed aiming to develop a high-temperature resistant composite matrix resin with excellent heat resistance and low temperature curing properties, and good adhesive property with the reinforcement. First, a highly heat-resistant acetylene-terminated polyimide (ATPI) was designed and screened by a material genome approach (MGA). And then ATPI was synthesized by 3,4'-oxydiphthalic anhydride, 3,4-oxydianiline and 3-ethynylaniline. The chemical structure was investigated by means of Fourier transform infrared spectrometer (FT-IR) and hydrogen nuclear magnetic resonance (¹H-NMR). By copolymerizing ATPI and poly(vinylsilylene ethynylenephenylenethynylene) (PSA) resin, poly(silicon-alkyne imide) (PSI) resin was prepared. The thermal curing behavior of PSI resin was investigated by differential scanning calorimetry (DSC), and the curing process was designed based on the result of DSC. The thermal stability of the cured PSI resin was analyzed by thermogravimetric analysis (TGA). The results showed that the decomposition temperature of 5% mass loss (T_d5) and carbon yield ratio at 800 °C (Y_r800) of the cured PSI resin were 573 °C and 85.9% respectively in nitrogen. The mechanical property of the cured PSI resin was characterized by universal testing instruments. The flexural strength of the cured PSI resin was up to 49.8 MPa, which was 1.5 times higher than that of PSA resin. Next, quartz and T800 carbon fiber reinforced PSI composites were prepared by compression molding or heat pressure tank molding process. The flexural strength and interlaminar shear strength (ILSS) of reinforced composites were measured by universal testing instruments. The flexural strength and ILSS of T800 carbon fiber reinforced composite reached 1 553 MPa and 84.1 MPa, respectively. After 350 °C treated for 100 h, ILSS could remain basically unchanged. The T800 carbon fiber composite material had good heat resistance and mechanical stability. The flexural strength and ILSS of quartz fiber reinforced composite were 539 MPa and 37.6 MPa, respectively. The dielectric property of quartz fiber reinforced composite was also studied. After 500 °C treated for 5 min, the dielectric constant of the material was basically unchanged compared with that at room temperature. The dielectric property of the quartz fiber composite material was stable at high temperature.