Struetures And Properties Of Bismaleimide/Poly(Phthalazinone Ether Sulfone) Blends

BMI resins possess many superior properties compared to the other materials, such as excellent chemical, corrosion resistance and low moisture absorption, which make them attractive candidates for matrix materials or molding materials in aerospace field and electronic industry. However, the applications of cured BMI are extremely limited because of their brittle characteristic. The problem has initiated a lot of research efforts for improving fracture toughness of the BMI resins recently. High-performance thermoplastics with high Tgs have been utilized to toughen BMI thermosets, the way is extremely advantageous to increase the fracture toughness and only slightly decrease the heat resistance. Poly (phthalazinone ether sulfone) (PPES) is a kind of novel high performance polymer. Their special structure endows them with excellent comprehensive properties, including outstanding thermal properties, good solubility and acceptable interfacial adhesion. It is a very good selection to toughen BMI resin in order to obtain high performance matrix resin.In this paper, novel PPES resin containing phthalazinone structure (DHPZ) was firstly prepared by designing the molecular weight and reactive ended groups, and used to modify BDM resin. Dynamic differential scanning calorimetry (DSC) was carried out to calculate kinetic parameters and determinated curing process. Evolution of phase separation was observed by Optical Microscopy (OM). The reaction-induced phase separation of blends with 10phr modifier was according to the characteristic of spinodal decomposition. The phase of blends was origined from decentralized structure to rules particle structure. The phase of blends with 15phr was origined from decentralized structure to continuous structure rules particle and fixed at particle structure. With varying PPES molecular weight, the phase separation mechanism didn't change, while the phase separation procedure and size of phase were different. The TGA results of the blend indicided the matrix possessed good thermal properties.We investigated the impact resistance of modified blends, the tendency of impact strength and impact critical stress intensity factor (KIC) of the blends with PPES first increases with the addition of PPES until to 15phr, then its highest value appear. These can indicate that the addition of PPES is beneficial to improve the blends toughness. Comparison of the PPES, PPES-BMI and PPES-DA composite showed the higher toughness and a similar regularity that the value of impact strength and KIC increase with the thermoplastic content but the tendency becomes more and more lenitive. The impact strength and critical stress intensity factor values got a maximum when 20phr PPES-DA and PPES-BMI was added. The flexural property of the blends with 15phr modifiers was investigated; flexure test showed that flexural strength of the blends is minor decreasing with addition of thermoplastic resin.Scanning electron microscope was used to investigate the fracture surfaces from specimens, micrograph of fracture surfaces showed PPES can improve toughness in a certain level. It may attribute that fracture toughness depends on cracks deflection and bifurcation, plastic deformation of matrix, the toughness of the thermoplastic and so on. For PPES-DA/BDM/DABPA and PPES-BMI/BDM/DABPA, functional groups can participate in curing reaction, decrease crosslinking density and introduce flexible chain segment. Simultaneously, functional groups can enhance the interfacial adhesion and compatibility in order to improve the toughness of blends.