The effect of t-butyl peroxybenzoate (TBPB) on the cure reaction of QY8911-3 resin (BMI) was studied by differential scanning calorimetry (DSC) and gel time analysis. The mechanical properties of the resin and the composite were tested and analyzed with the peroxide content. The results showed that TBPB decomposed between 117 and 191degreesC and the enthalpy was 1123 J/g. TBPB reduced the initial reaction temperature, prompted the reaction speed, and shortened the gel time of the BMI resin. TBPB also increased the bending strength and decreased the impacting strength of the postcured samples. So, the peroxide content should be less than 0.6%. CF/SiO2/BMI composites were prepared from the BMI containing peroxide and their microstructure and properties were better than those of the composites free of peroxide. According to the injection-molding experiment, the spilling problem was overcome and the forming time was reduced from 2 h to 15 min when peroxide was added. (C) 2003 Wiley Periodicals, Inc.