| Advanced polymer materials have excellent heat resistance,mechanical properties and functionality to meet the needs of aerospace,shipbuilding and electronic packaging industries.Compared with the widely used high-performance thermosetting resins at present,such as:Heat-resistant epoxy resin,thermosetting polyimide resin,bismaleimide resin and cyanate ester,etc.phthalonitrile resin has high heat resistance,good mechanical properties,strong flame retardancy,low dielectric and low water absorption,etc.With many excellent properties,phthalonitrile resin has become a hot spot in thermosetting resin research at present.The research on phthalonitrile started in 1970 s,and the related research started later in China.At present,there has been a breakthrough in the research of phthalonitrile resin from molecular modification to blending modification,including the research of carbon fiber and glass fiber reinforced phthalonitrile resin composites.Although phthalonitrile resin has a glass transition temperature(Tg)above 400?,it still has some problems to be solved,including narrow processing window,brittleness,low curing efficiency and high curing temperature.In view of these problems of phthalonitrile resin,this paper adopts long-chain thermoplastic resin to toughen phthalonitrile resin,so as to improve the toughness and functionality of phthalonitrile resin and improve the curing efficiency of phthalonitrile resin.The phthalonitrile resin studied in this paper is phenolic hydroxyl self-catalyzed phthalonitrile resin,in which the ratio of phthalonitrile group to phenolic hydroxyl group is 75:25,that is,phthalonitrile unit accounts for 75%,so the resin is called PN75 or PN for short.Autocatalytic phthalonitrile resin avoids the addition of small molecular catalyst,ensures the stability of resin structure in the curing process,and reduces the operation difficulty.Secondly,silicon hybrid phthalonitrile-terminated poly(arylene ether nitrile)resin(BPSiPEN)was selected as the second phase toughening agent and blended with phthalonitrile resin to improve its brittleness and low curing efficiency.In this paper,BPSiPEN and PN75 were blended by melt blending and solution blending,and the effects of BPSiPEN addition and content on the blended resin were studied.The results show that the addition of BPSiPEN can shorten the gel time and effectively improve the curing efficiency of phthalonitrile resin.By non-isothermal DSC analysis,when the addition of BPSiPEN is 5%,the apparent activation is sightly reduced,the decrease of apparent activation energy means that curing reaction is easier to occur.The blended resin was cured,and its bending strength and heat resistance were tested.The results show that the addition of BPSiPEN hardly affects the high heat resistance of phthalonitrile resin,and can effectively improve its toughness.The flexural strength of the blend resin increased by 44.96% and 26.96%,respectively,when BPSiPEN content was 5% and 7%.the fracture displacement increased by 54.29% and 13.41%.Therefore,BPSiPEN can improve the toughness and curing efficiency of phthalonitrile resin without damaging its high heat resistance.Moreover,the addition of BPSIPEN can effectively reduce the dielectric constant of phthalonitrile resin,The dielectric constant was stable at 2.07 with the addition of 7% BPSIPEN,which decreased by about 39.12%compared with that of phthalonitrile resin.Finally,carbon fiber reinforced composites with different BPSiPEN content were prepared,and their mechanical properties at normal temperature,high temperature stability,dynamic mechanical properties,water absorption and flame retardancy were tested.The results showed that the bending strength and interlaminar shear strength increased by about 25.27% and 5% when the content of BPSIPEN was 7%,and the heat resistance and functionality were almost lost or even better. |
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