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Herein, we fabricated a hybrid (mSiO 2 @ZrPB) by modifying mesoporous silica (mSiO 2 ) with zirconium N,N 0 -piperazine (bismethylene phosphonate) (ZrPB) via a selfassembly method, and studied the effects of the combination between mSiO 2 @ZrPB and 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phospha-phenantbrene-10-oxide (DOPO-HQ) on the curing behavior, flame retardancy, mechanical/thermal properties of epoxy/cyanate (EPCE) copolymer. The EPCE composite containing 8.0 wt% DOPO-HQ and 2.0 wt% mSiO 2 @ZrPB reaches UL-94V-0 with the highest limiting oxygen index of 30.5%, and exhibits a reduction of 34.1% on the peak heat release rate and a reduction of 26.8% on the total heat release compared with pure EPCE.The flame-retardant mechanism is mainly attributed to the catalyzing carbonization effect of both DOPO-HQ and mSiO 2 @ZrPB in the condensed phase. Moreover, the EPCE composites have improved thermal resistance (i.e., an increase in glass transition temperature). In addition, the tensile and impact strengths of the composite containing 9.0 wt% DOPO-HQ and 1.0 wt% mSiO 2 @ZrPB are respectively increased by 19.1% and 18.9%, with respect to those of pure EPCE. Moreover, the EPCE composites exhibit excellent dielectric properties. Additionally, the curing and thermaloxidative degradation behaviors of EPCE and its composites were investigated in more detail. The work provides a new strategy for preparation of EPCE composites with excellent comprehensive properties.flame/fire retardancy, mechanical properties, mesoporous silica hybrid, polymer-matrix composites, thermal properties | INTRODUCTIONEpoxy resin (EP) is widely applied in the fields of aviation, coating, electronics, and so forth owing to its superior adhesiveness, excellent chemical resistance and good mechanical properties. 1-5 However, with the rapid development of communication technologies (e.g., 5G), some properties of EP such as thermal resistance and dielectric properties cannot meet the requirements in the field of electronic encapsulation. In order to improve the drawbacks of EP mentioned above, cyanate ester resin (CE) is usually used to copolymerize with EP, because CE possesses outstanding features including high thermal stability, low dielectric constant and dielectric loss, and low moisture absorption. [6][7][8] Besides, CE can be mixed with any proportion of EP. The EP and CE copolymer (EPCE) has higher thermal resistance and much better dielectric properties than those of EP, which is possibly used in the fields of printed circuit boards, electronic encapsulants, and so forth. [9][10][11][12] It was reported that the initial thermal stability (e.g., the temperature at 5% weight loss) and thermal resistance

Epoxy resin (EP)/cyanate ester (CE) copolymer, an important structural material with high temperature resistance and low dielectric constant in aerospace, microelectronics, and related fields, is still of great flammability danger. In this work, copper phenyl phosphonate (CuPP), a flame retardant used in EP/CE copolymer was synthesized by the reaction of phenyl phosphonic acid and copper nitrate trihydrate. The fire and thermal behavior of EP/CE/CuPP composites were studied in detail. The results suggested that the UL-94 rating and limiting oxygen index of EP/CE composite with 5 wt% CuPP (EP/CE/CuPP5) reach V-1 level and 30.6%, respectively. Compared with pure EP/CE copolymer, the peak heat release rate and total heat release values of EP/CE/CuPP5 decreased by 34.5% and 18.9%, respectively. The glass transition temperature of EP/CE/CuPP composite is higher than that of pure EP/CE copolymer, suggesting that the fire-retardant composite has higher work temperature and better heat resistance.