Structure And Properties Of High Performance Bismaleimide Resin Composites Based On Metal Organic Frameworks

High performance heat-resistant thermosetting resin(HPTR)has been a critical base material that constrains the development prospects of cutting-edge industries such as electric information,insulation,new energy and aerospace.With the development of lighter weight,faster speed and higher power for products,the reliability of the service life puts forward more and more significant necessity.A large number of studies have shown that high dielectric loss is the main factor inducing easy aging and low servise reliability of electric and insulation applications.Therefore,the low dielectric loss becomes an important performance characteristic of high performance insulating materials including high heat resistance and good toughness.Bismaleimide resin(BMI)is a typical representative of HPTR and has important applications in cutting-edge areas such as electric information,insulation,new energy and aerospace.However,it is always an important research topic in the field of materials to develop composites with good toughness,high heat resistance,low dielectric constant and loss on the basis of maintaining outstanding performances of thermosetting resins.In addition,there has been no study on the flame retardancy of metal organic framework(MOF)modified resins.Based on above problems,two kinds of rigid MOFs,s MIL and aminated MOFs(sN-MIL),were prepared,and their structures were systematically characterized.Results show that compared with s MIL,sN-MIL has similar structure,and its particle size is about 100 nm,the BET specific surface area is 171.78 m2/g,which is much smaller than that of 3099 m2/g in literature.In addition,sN-MIL was added into allyl bisphenol A(DBA),which was then blended with bismaleimide(BMI)to prepare new kind of composites(sN-MIL/BD).The influences of sN-MIL on curing behavior,aggregation structure(cross-linking degree and free volume),heat resistance,dielectric properties and mechanical properties(including toughness and rigidity)as well as toughening mechanism and flame retardancy of BD resin were systematically studied.Results show that all sN-MIL/BD composites have ultralow dielectric loss,low dielectric constant,good heat resistance and excellent mechanical properties,including impact strength,flexural strength and critical stress intensity factor(KIC).Typically,for the composite with 0.3wt% sN-MIL(0.3sN-MIL/BD),its flexural strength,impact strength and KIC were 1.86,1.70 and 1.65 times higher than that of BD resin,respectively.At the same time,the dielectric loss of 0.3sN-MIL/BD is as low as 0.0004 at 100 Hz,which is the lowest value of filler/polymer composites so far and the dielectric constant(3.15)is also low.It is shown that sN-MIL prepared herein has excellent abilities of reducing dielectric loss as well as toughening and strengthening BD resin.In addition,the flame retardancy and flame retardant mechanism of sN-MIL/BD composites were studied in detail from the limit oxygen index,cone calorimetry and thermogravimetric analysis-infrared spectra.Studies have shown that the addition of sN-MIL increases the difficulty of catching fire,showing good flame retardancy.Aggregation structures(free volume,cross-linking density)of sN-MIL/BD composites were studied in detail.The mechanism of sN-MIL/BD composites was investigated.