| Bismaleimide is a composite resin matrix which has witnessed rapid growth in recent years.The self-aggregating polymer with highly crosslinked three-dimensional network structure possessed excellent features such as thermal stability,corrosion resistance,insulation and dimensional stability.Thus it is widely used in the industrial fields of aerospace,petrochemical,electronics,automotive,machinery and so on.However,the cured bismaleimide resin has high crosslinking density,increased brittleness and poor impact resistance and crack resistance.Those poor properties make it difficult to process or to meet the processing technology and industrial use performance requirements,limiting their further development and application.In this study,two series of hyper branched epoxy resin were prepared to modify bismaleimide resin blends by melting method.The structure and properties of blends were studied in order to obtain the bismaleimide modified resin with both excellent thermo stability and good toughness,and make it become a novel high performance resin matrix in composite materials field.The main research contents are as follows:Bismaleimide(BDM)/diallyl bisphenol A(DABPA)matrix resin was modified with aliphatic hyperbranched epoxy resin(AHEP),and the curing behavior of blending system was determined by Fourier transform infrared(FT-IR)and differential scanning calorimeter(DSC).We found that the epoxy groups in AHEP were involved in the reaction,whereas the DSC curve position was unchanged.The research results showed that the addition of AHEP did not change the curing mechanism of the blending system.The curing process of the blending system was determined by DSC test 160°C/2 h+180°C/2 h+230°C/4 h.Mechanical properties of blending cured product was studied by bending test and impact test.When mass fraction of AHEP was 10%,the bending strength(304 MPa)and impact toughness(32 kJ/m~2)of the cured solid were increased 76%and 10 times compared to the matrix resin,respectively.The result of TGA indicated that the addition of AHEP led the blend to have a slightly lower thermal stability than the matrix resin but it was of little effect.Fracture surface of blend was observed by scanning electron microscopy(SEM),and it appeared more fiber pull out phenomenon compared to the matrix resin.This demonstrated that the blends had a better fracture toughness which was consistent with impact test result.The blending system has a better comprehensive performance when mass fraction of AHEP was 7.5%by comprehensive comparison.Bismaleimide(BDM)/diaminodiphenyl methane(MDA)matrix resin was modified with hyperbranched epoxy resin with both rigid benzene ring structure and aliphatic chain(BHEP).The curing kinetics of the blends was studied by DSC and the curing process was as follows150°C/2 h+180°C/2 h+230°C/4 h.The epoxy groups in BHEP were involved in the copolymerization reaction which was investigated by FT-IR,and the result was consistent with the curing mechanism of DSC analysis.The mechanical properties of the blends were tested by bending test and impact test.When mass fraction of BHEP was 10%,the impact toughness(14 kJ/m~2)of the blends increased 25%compared to the matrix resin(11 kJ/m~2).When it was 5%,the bending strength(68 MPa)was best and increased 9%compared to the matrix resin.The analysis result of TGA revealed that the addition of BHEP improved the thermal stability of blends.Moreover,we discovered that the surface of the blends exhibited a better ductile fracture characteristic by SEM,which was aligned with the impact test result.The blending system has a better comprehensive performance when mass fraction of BHEP was 5%by comprehensive comparison. |
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